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Green tea effects on cognition, mood and human brain function: A systematic review

Affiliations.

1 University of Basel, Department of Psychiatry, Wilhelm Klein Str. 27, 4012 Basel, Switzerland.
2 University Hospital Basel, Department of Gastroenterology, 4031 Basel, Switzerland.
3 University of Basel, Department of Psychiatry, Wilhelm Klein Str. 27, 4012 Basel, Switzerland; King's College London, Institute of Psychiatry, Department of Psychosis Studies, London, United Kingdom. Electronic address: [email protected].
PMID: 28899506
DOI: 10.1016/j.phymed.2017.07.008

Background: Green tea (Camellia sinensis) is a beverage consumed for thousands of years. Numerous claims about the benefits of its consumption were stated and investigated. As green tea is experiencing a surge in popularity in Western culture and as millions of people all over the world drink it every day, it is relevant to understand its effects on the human brain.

Purpose: To assess the current state of knowledge in the literature regarding the effects of green tea or green tea extracts, l-theanine and epigallocatechin gallate both components of green tea-on general neuropsychology, on the sub-category cognition and on brain functions in humans.

Methods: We systematically searched on PubMed database and selected studies by predefined eligibility criteria. We then assessed their quality and extracted data. We structured our effort according to the PRISMA statement.

Outcome: We reviewed and assessed 21 studies, 4 of which were randomised controlled trials, 12 cross-over studies (both assessed with an adapted version of the DELPHI-list), 4 were cross-sectional studies and one was a cohort study (both assessed with an adapted version of the Newcastle-Ottawa assessment scale). The average study quality as appraised by means of the DELPHI-list was good (8.06/9); the studies evaluated with the Newcastle-Ottawa-scale were also good (6.7/9).

Conclusions: The reviewed studies presented evidence that green tea influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI). The effects of green tea cannot be attributed to a single constituent of the beverage. This is exemplified in the finding that beneficial green tea effects on cognition are observed under the combined influence of both caffeine and l-theanine, whereas separate administration of either substance was found to have a lesser impact.

Keywords: Brain functions; Cognitive functioning; Green tea.

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Published: 10 July 2020

Effects of green tea consumption on glycemic control: a systematic review and meta-analysis of randomized controlled trials

Renfan Xu 1 ,
Yang Bai 2 ,
Ke Yang 2 &
Guangzhi Chen ORCID: orcid.org/0000-0003-2004-1486 2

Nutrition & Metabolism volume 17 , Article number: 56 ( 2020 ) Cite this article

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The results of human clinical trials investigating the effects of green tea on glycemic control are inconsistent.

We conducted a systematic review and meta-analysis of RCTs that examined the effects of green tea supplementation on glycemic control. A literature search in PubMed, Embase, and Cochrane Library databases for RCTs that investigated the effect of green tea consumption on glycemic control was performed up to February 2020. A random-effects model was used to estimate weighted mean difference (WMD) with 95% confidence intervals (CIs).

Twenty-seven trials involving 2194 subjects were included in the meta-analysis. The pooled results showed that green tea significantly lowered fasting blood glucose by − 1.44 mg/dL (95%CI:-2.26, − 0.62 mg/dL; P < 0.001) with no obvious heterogeneity ( I 2 = 7.7%). However, green tea consumption did not significantly affect fasting insulin and HbA1c values. The mean differences were − 0.46μIU/mL (95% CI: − 1.10, 0.17 μ IU/mL; P = 0.21) for fasting insulin and − 0.06%; (95% CI: − 0.12, 0.01%; P = 0.07) for HbA 1c concentrations. Heterogeneity was significant in fasting insulin ( I 2 = 46.8%) and mild in HbA 1c ( I 2 = 1.7%).

Conclusions

In short-term trials, green tea supplementation significantly reduced fasting glucose, but had no significant effect on fasting insulin and HbA 1c . Long-term trials assessing the effects of green tea supplementation on glycemic control are needed.

Introduction

Type 2 diabetes mellitus (T2DM) is a significant global public health challenge [ 1 ]. By the end of 2017, more than 451 million people were living with T2DM worldwide. Moreover, this number is projected to rise to 693 million by 2045 [ 2 ]. T2DM is one of the leading risk factors for premature mortality [ 3 ]. In addition, T2DM is associated with adverse health outcomes including heart attack, stroke, blindness, kidney failure, and amputation [ 4 ]. In prediabetic individuals with impaired glucose tolerance or fasting glucose, lifestyle modification can decelerate the progression to T2DM [ 3 ] . However, it is difficult to achieve and sustain sufficient lifestyle intervention. Although medications may play a role in delaying the onset of diabetes, long-term usage may be costly and associated with various side effects. Plants have always been an important source of drugs, and many currently available drugs were either directly or indirectly derived from plants [ 5 ]. Herbal drugs are widely used for their effectiveness, relatively low cost, and fewer side effects.

Green tea is produced from the fresh leaves of Camellia sinensis and has played an important dietary and medicinal role throughout history, particularly in Asian countries. Green tea contains a variety of effective compounds including antioxidants, vitamins, carbohydrates, protein, minerals, and flavonoid-like polyphenols [ 6 ], which may be beneficial in the prevention of diabetes. The most prominent effects of green tea on human health are mainly attributed to catechins, which belong to the flavonoid-like polyphenols family. The four major catechins found in green tea extract are epicatechin (EC), epigallocatechin (EGC), epicatechingallate (ECG), and epigallocatechingallate (EGCG) [ 7 ].

A previous meta-analysis with 17 randomized controlled trials (RCTs) suggested that green tea consumption resulted in a significant reduction in fasting blood glucose (FBG) and glycated hemoglobin (HbA 1c ) [ 8 ]. In addition, a meta-analysis with 9 cohort studies showed that green tea consumption was associated with a significant reduction of T2DM risk [ 9 ]. Both in vitro and animal experiments have shown that green tea catechins, especially EGCG can significant improve glycemic control as well as insulin sensitivity and may lower insulin requirement [ 10 , 11 ]. However, findings from randomized controlled trials (RCTs) on green tea supplementation and glycemic control or insulin sensitivity in individuals with preclinical diabetes or T2DM are debatable. Some studies observed that green tea significantly improve glycemic control [ 12 ], whereas others found no significant association between green tea intake and glycemic control [ 13 , 14 ].

Given the inconsistency of prior clinical studies and the limitations in these previous meta-analyses, such as the inadequate consideration of possible confounding factors and lower number of included references, we performed a systematic review and meta-analysis to update the evidence which quantitatively assess the effect of green tea supplementation on measures of glucose control and insulin sensitivity.

Search strategy and eligibility criteria

This systematic review and meta-analysis was conducted in accordance with the recommendations outlined in the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement [ 15 ]. Relevant English-language articles were identified via searches in PubMed, Embase, and the Cochrane Library from the index date of each database through February 2020. The search terms were as follows: “green tea,” “green tea extract,” “tea component(s),” “tea solid(s),” “tea polyphenols,” “catechin,” “catechins,” “EGCG,” and “ Camellia sinensis ,” which were paired with the following words: “glucose,” “glyc(a)emia,” “hyperglycaemia,” “glucose control,” “insulin,” “insulin sensitivity,” “insulin resistance,” “HbA 1c ,” “glycated protein,” “fructosamine,” and “diabetes”. Additional studies were identified by manually screening the reference of originally identified reviews and research reports or the clinical trials. The search was confined to studies involving humans.

Study selection

The prespecified inclusion criteria were as follows: 1) RCTs with both parallel and crossover interventions, 2) study involved adult subjects who consumed green tea for≥2 weeks, 3) blood glucose was evaluated by estimating the concentrations of FBG, fasting blood insulin (FBI) and HbA 1c , and 4) the study used a concurrent control group with the only difference between the treatment and control groups being the consumption of either green tea or green tea extract. The exclusion criteria were as follows: 1) subjects in each group ≤10, 2) green tea extract was given as part of a multicomponent supplement,3) RCTs that did not report mean (SD) changes in fasting glucose, fasting insulin, or HbA 1c in each treatment group and could not be calculated from the data available. The data from multiple published reports involving the same study population were included only once.

Quality assessment

Two review authors (CGZ and XRF) independently assessed the study quality and any disagreement was resolved by discussion between the third author (YK). Jadad scoring criteria was used in which a study was judged on 0–5 points (5 reflected the highest quality). With this system, one point was allocated to each for 1) randomization; 2) double blinding (participant and researcher masking); 3) reporting the number of and reasons for withdrawal; 4) generation of random numbers; and 5) allocation concealment. Trials were considered of high-quality if the Jadad score was ≥4, while trials were classified as low-quality if the Jadad score was < 4 [ 16 ].

Data extraction

Two authors (CGZ and XRF) independently extracted the data, and any discrepancies between the two reviewers were resolved through discussion with a third author (BY). The following information was recorded using a standardized electronic form: study characteristics (the first author, publication year, study design, study duration, sample size, intervention type, and dosage), population information (age, sex, country, and baseline fasting glucose), and baseline and final concentrations or net changes of FBG, FBI, HbA1c and homeostatic model assessment of insulin resistance (HOMA-IR). Studies with multiple dosages of green tea or multiple control groups were included separately in the meta-analysis.

Statistical analysis

A meta-analysis was performed with the use of the STATA statistical software (version 11; STATA Corp LP). For parallel trials, the treatment effects were calculated as the weighted mean difference (WMD) and standard deviation (SD) in the change from baseline to follow-up in the green tea group versus control group. For crossover trials, the treatment effects were calculated as the WMD and SD at follow-up in the green tea intervention versus control periods. If the SD were not reported directly, the variances were imputed from 95% CIs, P values, standard error (SE), or t values [ 17 ]. In addition, missing SD values for paired differences were imputed by assuming a correlation coefficient of 0.5 between variances at baselines and completion of trials according to the method of Follmann et al. [ 18 ]. The statistical heterogeneity of treatment effects between studies was evaluated via the Cochran’s Q test ( P < 0.1 was considered significant) and the inconsistency index ( I 2 ). I 2 > 50% indicated significant heterogeneity across studies [ 19 ]. Random-effects models (DerSimonian and Laird), which considered both within- and between-study variation, were performed for the studies used different doses, different populations, different durations and so on [ 20 ]. Primary outcome measures included WMD in FBG, FBI, and HbA 1c after green tea supplementation. The secondary outcome measures included WMD in HOMA-IR concentration.

Sensitivity analyses were used to evaluate the stability of the results by removing a single study each time to identify the effect of individual studies on the pooled effect size. Prespecified subgroup analyses were performed by catechins dosage (≥500 mg/d compared with < 500 mg/d), intervention type (green tea beverage compared with green tea capsule), participants’ country (Asian compared with Western countries), study design (parallel compared with crossover), baseline fasting glucose level (high or normal), trial quality (low risk of bias, some concern or high risk of bias) and treatment duration (≥12 weeks compared with < 12 weeks). In addition, the study duration< 12 weeks were defined as short duration for the changes of HbA 1c need to be monitored for at least 2–3 months. Meta-regression analysis was performed to examine the association between the net change in fasting glucose, fasting insulin or HbA 1c and intervention dose, treatment duration, intervention type, caffeine content, different ethnicity or study design. Publication bias was assessed by funnel plots and Egger’s test [ 21 ]. A P value of < 0.05 was considered statistically significant, unless otherwise specified.

Results of the literature search

The search strategy identified 2324 abstracts. After the titles and abstracts were screened, 2229 articles were excluded and 95 articles underwent full-text review. A further 68 articles were excluded for the following reasons: 26 articles did not provide relevant outcomes, 14 articles involved green tea as a multicomponent supplement in the experimental group, 12 articles were excluded because the subjects had been treated with black tea or oolong tea.

5 studies were less than 2 weeks in duration and 11 articles did not report sufficient details for inclusion. Finally, 27 eligible articles met the inclusion criteria and were included in the meta-analysis (Fig. 1 ).

Flow diagram of the trial selection process

Study characteristics

Twenty seven eligible RCTs [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] were enrolled in this meta-analysis (Table 1 ). Twenty seven studies [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] with 2194 subjects reported on FBG, 18 studies [ 23 , 24 , 25 , 26 , 27 , 29 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 39 , 43 , 44 , 48 ] with 1559 subjects reported data on FBI and 11 studies [ 22 , 24 , 27 , 31 , 32 , 34 , 37 , 40 , 41 , 43 , 48 ] with 767 subjects reported data on HbA 1c . The green tea catechins intake ranged from 80 to 1344 mg/d, the trial size varied from 25 to 240 subjects and the study duration ranged from 3 weeks to12 months. (Table 1 ).

Of the 27 trials with 28 comparisons included in the current meta-analysis, 13 comparisons [ 22 , 23 , 24 , 25 , 28 , 29 , 30 , 33 , 36 , 39 , 46 , 48 ] were conducted in western countries and 15 comparisons [ 26 , 27 , 31 , 32 , 34 , 35 , 37 , 38 , 40 , 41 , 42 , 43 , 44 , 45 , 47 ] were conducted in Asian countries. Twenty comparisons [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 33 , 36 , 38 , 39 , 41 , 42 , 45 , 46 , 47 , 48 ] were performed in subjects with normal FBG and 8 comparisons [ 31 , 32 , 34 , 35 , 37 , 40 , 43 , 44 ] were performed in subjects with high level FBG. Most comparisons (25 of 28) used a parallel study design [ 22 , 23 , 24 , 26 , 27 , 28 , 29 , 30 , 31 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 45 , 46 , 47 , 48 ], while others (3 comparisons) used a crossover design [ 25 , 32 , 44 ]. Twelve comparisons [ 22 , 24 , 25 , 27 , 29 , 33 , 35 , 37 , 38 , 39 , 48 ] adjusted for the confounding effect of caffeine on glucose and insulin, 13 comparisons [ 26 , 28 , 30 , 31 , 32 , 34 , 36 , 40 , 41 , 42 , 43 , 44 , 45 ] used caffeinated green tea, and 3 [ 23 , 46 , 47 ] did not report the use of coffee. Twenty comparisons [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 46 , 47 , 48 ] used green tea extract capsule and eight comparisons [ 22 , 31 , 32 , 41 , 42 , 43 , 44 , 45 ] used green tea beverage (Table 1 ).

Data quality

The study quality of the 27 included RCTs varied. Fourteen studies [ 22 , 23 , 24 , 25 , 26 , 27 , 29 , 34 , 35 , 38 , 39 , 45 , 46 , 47 ] were classified as high-quality (Jadad score ≥ 4), and the remaining 13 studies [ 28 , 30 , 31 , 32 , 33 , 36 , 37 , 40 , 41 , 42 , 43 , 44 , 48 ] were classified as low-quality (Jadad score < 4). Most trials did not report details regarding allocation concealment (14 of 27) [ 26 , 28 , 30 , 31 , 32 , 36 , 37 , 40 , 41 , 42 , 43 , 44 , 46 , 48 ] or randomization method (15 of 27) [ 23 , 28 , 30 , 31 , 32 , 33 , 36 , 37 , 40 , 41 , 42 , 43 , 44 , 45 , 48 ]. Twenty-two trials used double-blinded design [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 45 , 46 , 47 , 48 ], one trial used a single-blinded design [ 22 ], and four trials used an open-label design [ 31 , 32 , 33 , 44 ]. Three trials did not report the dropout rate or the reasons for the dropouts [ 28 , 40 , 44 ] (Table 2 ).

Main outcomes

Primary outcome measures included changes in FBG, FBI, and HbA 1c . Overall, green tea supplementation significantly decreased FBG concentration by − 1.44 mg/dL (95%CI:-2.26, − 0.62 mg/dL; P < 0.001). Heterogeneity was not significant for this outcome ( I 2 = 7.7%, P = 0.35) (Fig. 2 ). Green tea supplementation had no significant effect on FBI concentrations in the overall analysis (WMD: − 0.46μIU/mL; 95%CI: − 1.10, 0.17 μ IU/mL; P = 0.21). The overall test for heterogeneity was significant ( I 2 = 46.8%; P = 0.01) (Fig. 3 ). In addition, there was no significant difference in serum HbA 1c concentration between green tea supplementation and placebo group (WMD: − 0.06%; 95% CI: − 0.12, 0.01%; P = 0.07), with mild heterogeneity ( I 2 = 1.7%; P = 0.43) (Fig. 4 ).

Meta-analysis of the effects of green tea on fasting blood glucose concentrations. Results from individual trials were pooled with the use of random-effect models and are expressed as weighted mean differences with 95% CIs

Meta-analysis of the effects of green tea on fasting blood insulin concentrations. Results from individual trials were pooled with the use of random-effect models and are expressed as weighted mean differences with 95% CIs

Meta-analysis of the effects of green tea on HbA lc concentrations. Results from individual trials were pooled with the use of random-effect models and are expressed as weighted mean differences with 95% CIs

Secondary outcome measures included changes in HOMA-IR concentration. Green tea supplementation had no significant effect on HOMA-IR (WMD: -0.15; 95%CI:-0.39, 0.10; P = 0.24) compared with controls. Heterogeneity was not significant for this outcome ( I 2 = 34%, P = 0.12).

Subgroup analysis and meta-regression

In the subgroup analysis, green tea consumption significantly lowered FBG concentrations in subjects using green tea capsule or with high catechins dosage, subjects from western countries, subjects in short duration of green tea supplementation, subjects with normal FBG, studies with caffeinated green tea intake, studies with parallel design, and studies with low quality. However, significant reduction in fasting glucose was not found in other subgroups. In addition, the beneficial effect for green tea supplementation on fasting insulin was observed in subjects with green tea capsule, subjects from western countries, subjects with normal baseline FBG and studies with decaffeinated green tea intake. However, no effect was found in other subgroups. Significant reductions in HbA 1c concentrations were observed in subjects from Asian countries, studies with caffeine in green tea and studies with low quality, while the obvious effect was not found in other subgroups (Table 3 ).

Meta-regression found no linear relations between WMD in FBG, FBI or HbA 1C and intervention dose (Fig. 5 ). Furthermore, meta-regression found no linear relations between WMD in FBG or FBI and treatment duration, caffeine content, different ethnicity, intervention type and study design. In contrast, meta-regression by intervention type (beverage or capsule) did impact the WMD in HbA 1C for green tea consumption versus control group ( P = 0.021), while, there was no linear relations between WMD in HbA 1C and other subgroups.

a Relation between the WMD of FBG and intervention dose in 27 independent randomized controlled comparisons. b Relation between the WMD of FBI and intervention dose in 18 independent randomized controlled comparisons. c Relation between the WMD of HbA lc and intervention dose in 11 independent randomized controlled comparisons. Each circle represents a study, telescoped by its weight in the analysis. Meta-regression found no linear relations between WMD in FBG ( P = 0.89), FBI ( P = 0.97), or HbA lc ( P = 0.25) and intervention dose

Publication bias

The funnel plots of the studies were symmetrical for fasting glucose, fasting insulin, and HbA 1c (Supplementary Figure 1 ). Furthermore, the results of the Egger’s test did not support the existence of publication bias for fasting glucose ( P = 0.18), fasting insulin ( P = 0.58), and HbA 1c ( P = 0.45).

A sensitivity analysis was performed to confirm the robustness of our findings. In a sensitivity analysis, in which one study was removed at a time and the remaining studies analyzed, the pooled reductions in fasting glucose ranged from − 1.55 mg/dL (95% CI: − 2.39, − 0.70 mg/dL) to − 1.16 mg/dL (95% CI: − 2.10, − 0.22 mg/dL); and the pooled reductions in fasting insulin ranged from − 0.59 (95% CI: − 1.21, 0.02) to − 0.23 (95% CI: − 0.87, 0.42). The result was consistent after removing each trial for both fasting glucose and fasting insulin. In the sensitivity analysis of HbA 1c , the exclusion of one trial [ 22 ] (Basu 2011) resulted in significant reductions of-0.08 (95% CI: − 0.14, − 0.01) in HbA 1c . However, there was no significant reduction in HbA 1c after the removal of other trials.

This meta-analysis involving 27 RCTs with 2194 subjects evaluated the effect of green tea supplementation on glycemic control. We found that green tea supplementation significantly reduced FBG concentration, while the effect of green tea on other glycemic variables such as FBI, HbA 1c , and HOMA-IR was not significant.

Our results are consistent with some previous meta-analysis [ 49 , 50 ], which also showed that green tea consumption resulted in a significant reduction in FBG. While, another previous meta-analysis [ 8 ] suggested that green tea consumption had favorable effects on decreasing both FBG and HbA 1c concentrations. In our study, we did not find a significant improvement in HbA 1c concentrations. In more than half of the included trials, the intervention duration was less than 12 weeks. However, HbA 1c changes need to be monitored for at least 2–3 months when evaluating the progression of diabetes. Observational prospective cohorts and case-control studies have been performed to determine the effect of green tea supplementation on glycemic control, although the results are conflicting. In particular, A large epidemiological study conducted in Japan have indicated that daily tea consumption (> 6 cups/day) was associated with a decreased risk for diabetes [ 51 ] . Some RCTs also found beneficial effects on glycemic control, including reducing fasting glucose and fasting insulin [ 38 , 48 ]. In contrast, several RCTs have reported no significant correlations between green tea intake and glycemic control [ 24 , 27 ]. Nonetheless, these results need to be interpreted with caution because the number of patients enrolled in most trials was too limited, at less than 100 patients; in addition, the intervention duration and catechins dosages were varied among studies. So, more RCTs with larger subjects and longer duration were needed to find out the real relationship between green tea consumption and blood glucose control.

Recent mechanistic studies have examined the effects of green tea consumption on glucose control and provided further evidence for the biological plausibility of these findings. Green tea may affect glucose control through different mechanisms. First, tea catechins have been reported to reduce carbohydrate absorption from the intestine via inhibition of intestinal sucrose, alpha-amylase, and alpha-glucosidase [ 10 ]. Second, Tea catechins might also inhibit the hepatic gluconeogenesis through regulation of the expression of gluconeogenic genes and protein-tyrosine phosphorylation in the mouse liver [ 52 ]. Third, tea catechins could enhance insulin sensitivity and glucose metabolism there by helping to prevent the development of T2DM [ 53 ]. Furthermore, Tea catechins are also powerful antioxidants that can ameliorate oxidative stress [ 54 ].

In this meta-analysis, subgroup analyses were performed based on predefined variables to identify potential sources of heterogeneity. Green tea consumption significantly decreased FBG and FBI only in subjects using green tea capsule. In addition, meta-regression also pointed out that green tea capsule was associated with HbA 1C . Nowadays, there was still insufficient evidence on whether green tea capsule was more biologically active compared to green tea beverage in vivo or vitro studies. In addition, subgroup analyses revealed that green tea with caffeine had a more pronounced effect on FBG and HbA 1C than the decaffeination subgroup. As tea naturally contains caffeine in addition to catechins and other compounds, whether caffeine intake influences the glucose control of tea remains controversial [ 55 , 56 ]. As there were a limited number of subjects in the subgroup analysis, these results may not be generalized.

Our study had several strengths. First, we only selected RCTs in this meta-analysis, which ensured a relatively high-quality and provided reliable inference about causality. Second, both parallel and crossover studies were included in this meta-analysis. Crossover trials are generally considered to have a more-robust design than parallel trials because of reduced intraparticipant variability. We considered it important to include all these studies because they represented a comprehensive evidence for our analysis. Third, results were less likely to be influenced by publication bias. Furthermore, subgroup analyses were undertaken to detect potential sources of heterogeneity for primary outcomes.

Our study also had several limitations. First, the studies had relatively short durations of follow-up ranging from 3 weeks to 12 months. The intervention durations were less than 12 weeks in almost half of the included studies. In particular, HbA 1c changes need to be monitored for at least 2–3 months when evaluating the progression of diabetes. HbA 1c is an important indicator for glucose control, including greater pre-analytical stability, greater convenience, and less day-to-day perturbations. In addition, it also takes a number of months to detect delayed effects of green tea on insulin resistance. Therefore, RCTs with at least 3 months intervention duration might be more appropriate to assess the effects of green tea on glycemic control. Second, although significant effect of green tea intake on fasting glucose was observed in our study, we did not provide an optimal dosage of green tea supplementation that would maximize the improvement of glycemic control as the catechin dosage varied from 80 to 1344 mg/d and no consensus has been achieved. In addition, we could not ascertain the safety margin in this meta-analysis because no serious side effects were reported in the included trials. However, mild side effects such as mild skin rashes, gastric disturbances, and abdominal bloating were reported in some clinical studies [ 57 ]. Third, the size of these trials, which ranged between 25 and 240 participants, were indeed limited. Therefore, our meta-analysis may have been underpowered to detect a true effect. Forth, the quality of RCTs included in this meta-analysis varied. Some of the RCTs did not provide detailed randomization process. Of the 27 trials, almost half of the trials were of high risk of bias, which may also affect the reliability of our findings.

In conclusion, green tea intake had a favorable effect on fasting blood glucose concentration. However, green tea intake did not significantly affect fasting blood insulin or HbA 1c . In future, high-quality larger RCTs with long-term follow-up are needed to investigate the effect of green tea supplementation on glycemic control, especially the long-term effects on fasting insulin and HbA 1c .

Availability of data and materials

All data generated or analyzed during this study are included in this published article.

Abbreviations

Confidence intervals

Epigallocatechin gallate

Fasting blood glucose

Fasting blood insulin

Glycated hemoglobin

Homeostatic model assessment of insulin resistance

Systematic Reviews and Meta-Analyses

Randomized placebo-controlled trials

Standard deviation

Standard error

Type 2 diabetes mellitus

Weighted mean difference

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The present study was supported by the National Natural Science Foundation of China (No. 81500293).

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Additional file 1: figure 1..

A. Funnel plot of green tea supplementation and FBG. B. Funnel plot of green tea supplementation and FBI. C. Funnel plot of green tea supplementation and HbA lc .

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Xu, R., Bai, Y., Yang, K. et al. Effects of green tea consumption on glycemic control: a systematic review and meta-analysis of randomized controlled trials. Nutr Metab (Lond) 17 , 56 (2020). https://doi.org/10.1186/s12986-020-00469-5

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DOI : https://doi.org/10.1186/s12986-020-00469-5

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Regular consumption of green tea as an element of diet therapy in drug-induced liver injury (dili).

1. Introduction

2. methodology of information retrieval in databases, 3. pathophysiological mechanisms of dili, 4. effect of gut microbiota on liver function, 5. the potential of green tea as a component of dietotherapy in dili, 5.1. phenolic compounds in green tea, 5.2. hepatoprotective effects of green tea, 5.3. the antioxidant action of green tea, 5.4. anti-inflammatory action of green tea, 5.5. anti-obesogenic and anti-diabetic effects of green tea, 5.6. impact of green tea on gut microbiota, 6. controversies, 7. summary and perspectives, author contributions, institutional review board statement, conflicts of interest.

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Click here to enlarge figure

Characteristic	Duration of the Study	Disease	Dosage of Green Tea	Antioxidant Parameters	Liver Parameters	Type of Study	Reference
Control n = 40 Experimental n = 40	12 weeks	Non-alcoholic fatty liver disease	500 mg/day of GTE		↓ ALT, ↓ AST	Double-blind, placebo-controlled, randomized clinical trial	[ ]
Control n = 40 Experimerntal n = 80	12 weeks	Non-alcoholic fatty liver disease	1000 mg/day of GTE		↓ ALT, ↓ AST, ↓ hs-CRP	Double-blind, placebo-controlled, randomized clinical trial	[ ]
Control n = 20 Experimental n = 20	12 weeks	Moderate hypercholesterolemia	2 × 300 mL catechin-enriched green tea/day	↑ TEAC, ↑ GSH, ↑ SOD, ↑ CAT, ↑ GPx, ↑ GR	reverting mild fatty liver to the normal hepatic condition	Randomized, controlled trial	[ ]
Control n = 12 Experimental n = 26	6 months	Non-alcoholic steatohepatitis	600 mg/day catechins		↓ ALT, ↓ AST	Double-blind, placebo-controlled, randomized clinical trial	[ ]
Control n = 24 Experimental n = 21	3 months	Non-alcoholic fatty liver disease	550 mg/day green tea tablets		↓ AST	Placebo-controlled, randomized clinical trial	[ ]
Control n = 16 Experimental n = 16	4 weeks	Operating room staff chronically exposed to inhalation anesthetics			↓ AST, ↓ ALT, ↓ ALP, ↓ bilirubin	Placebo-controlled, randomized clinical trial	[ ]

	Animal Species	Duration of Experiment	Treatments	Dosage of Green Tea	Antioxidant Parameters	Liver Parameters	Anti-inflammatory Indices	Tissues	References
Control n = 6 Experimental n = 18	Male Wistar rats	28 days	Intraperitoneal injections of N-nitrosodimethylamine in a dose of 1 mg/100 g body weight on 3 consecutive days of a week	0.2 mg EGCG/100 g body weight	↓ MDA	↓ ALT, ↓ AST		Serum	[ ]
Control n = 5 Experimental n = 25	Male and female mice ICR	7 days	Stress-induced liver injury and immunosuppression	40 mg EGCG/kg		↓ ALT, ↓ AST	↓ IL-1β, ↓ IL-2, ↓ IL-6	Serum, liver	[ ]
Control n = 6 Experimental n = 22	Female Sprague–Dawley rats	8 weeks	Non-alcoholic fatty liver disease	50 mg EGCG/kg	↓ iNOS, ↓ COX-2, ↓ TNF-α	↓ ALT,↓AST ratio, ↓ number of fatty score, necrosis	↓ inflammatory foci	Serum, liver	[ ]
Control n = 8 Experimental n = 32	Male C57BL/6 mice	4 weeks	Methionine- and choline-deficient diet-induced non-alcoholic steatohepatitis	25, 50, or 100 mg EGCG/kg		↓ ALT, ↓ AST		Serum	[ ]
Control n = 5 Experimental n = 30	Female C57BL/6 mice	4 days	CCl -induced liver injury	100 mg GTE/kg		↓ ALT, ↓ AST, ↓ liver index		Serum, liver	[ ]
Control n = 6 Experimental n = 18	Male ICR mice	7 days	Lipopolysaccharide-induced inflammatory liver injury	100 or 200 mg green tea polyphenols/kg body weight	↓ MDA, ↓ GSH, ↑ SOD	↓ ALT, ↓ AST	↓ IL-1β, ↓ IL-18, ↓ IL-6, ↓ TNF-α	Serum, liver	[ ]
Control n = 6 Experimental n = 24	Male Sprague–Dawley rats	2 months	Thioacetamide-induced liver injury	250 mg/kg or 500 mg/kg daily methanolic GTE	↓ MDA, ↑ SOD, ↑ CAT	↓ ALT, ↓ AST, ↓ ALP, ↓ bilirubin		Serum, liver	[ ]
Control n = 12 Experimental n = 36	Male C57BL/6J mice	4 weeks	Methionine–choline-deficient diet-induced non-alcoholic steatohepatitis	50 mg/kg EGCG		↓ ALT		Serum	[ ]
Control n = 12 Experimental n = 6	Male C57BL/6J mice	14 weeks	High-fat diet-induced non-alcoholic fatty liver disease	EGCG—50 mg/kg/day	↓ ROS, ↑ GPx, ↑ SOD, ↑ CAT	↓ ALT, ↓ AST		Serum, liver	[ ]
Control n = 12 Experimental n = 48	Adult male Wistar rats	6 or 12 weeks	7 mg CdCl2 + 50 mg Pb(CH COO) per kg of feed	Green tea infusion (contains 111 mg tannic acid) per 1000 mL H O	↑ SOD, ↑ CAT, ↑ GPx			Liver	[ ]
Control n = 20 Experimental n = 23	Male Nrf2-null mice, male C57BL6 WT mice	8 weeks	High-fat diet-induced non-alcoholic steatohepatitis	2% GTE	↓ MDA	↓ ALT	↓ TNF-α	Liver	[ ]
Control n = 8 Experimental n = 24	Male Wistar rats	1 week	Halathion 150 mg/kg by gavage	30 mg/kg green tea through intraperitoneal injection	↓ LPO, ↑ TAP, ↑ TTG	↓ ALT, ↓ AST, ↑ ChE		Plasma, liver	[ ]
Control n = 20 Experimental n = 40	Adult mice Balb-C strain	12 weeks	High-fat and high-cholesterol diet-induced hepatic steatosis	1% green tea over in food		↓ ALT, ↓ AST, ↓ ALP		Serum	[ ]
Control n = 10 Experimental n = 30	Male Kunming mice	12 weeks	D-galactose-induced liver ageing	0.05% green tea polyphenols diet	↑ SOD, ↑ CAT, ↑ GSH, ↑ GST, ↑ TAC, ↓ MDA, ↓ NO	↓ ALT, ↓ AST, ↓ ALP	↓ TNF-α, ↓ TGF-β, ↓ IL-1β, ↓ IL-6		[ ]

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Winiarska-Mieczan, A.; Jachimowicz-Rogowska, K.; Kwiecień, M.; Borsuk-Stanulewicz, M.; Tomczyk-Warunek, A.; Stamirowska-Krzaczek, E.; Purwin, C.; Stryjecka, M.; Tomaszewska, M. Regular Consumption of Green Tea as an Element of Diet Therapy in Drug-Induced Liver Injury (DILI). Nutrients 2024 , 16 , 2837. https://doi.org/10.3390/nu16172837

Winiarska-Mieczan A, Jachimowicz-Rogowska K, Kwiecień M, Borsuk-Stanulewicz M, Tomczyk-Warunek A, Stamirowska-Krzaczek E, Purwin C, Stryjecka M, Tomaszewska M. Regular Consumption of Green Tea as an Element of Diet Therapy in Drug-Induced Liver Injury (DILI). Nutrients . 2024; 16(17):2837. https://doi.org/10.3390/nu16172837

Winiarska-Mieczan, Anna, Karolina Jachimowicz-Rogowska, Małgorzata Kwiecień, Marta Borsuk-Stanulewicz, Agnieszka Tomczyk-Warunek, Ewa Stamirowska-Krzaczek, Cezary Purwin, Małgorzata Stryjecka, and Marzena Tomaszewska. 2024. "Regular Consumption of Green Tea as an Element of Diet Therapy in Drug-Induced Liver Injury (DILI)" Nutrients 16, no. 17: 2837. https://doi.org/10.3390/nu16172837

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The green tea effect: From gut microbes to weight loss, new insights emerge

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In a recent study published in the Foods Journal, a group of researchers investigated the impact of green tea and its functional components on body weight and gut microbiota regulation.

The study was undertaken in mice fed with a high-fat (HF) diet and also identified potential obesity markers via 16S ribosomal ribonucleic acid (16S rRNA) gene sequencing.

Study: The Role of Green Tea on the Regulation of Gut Microbes and Prevention of High-Fat Diet-Induced Metabolic Syndrome in Mice. Image Credit: grafvision/Shutterstock.com

Obesity, affecting over 500 million people globally, leads to multiple metabolic diseases, including high blood pressure and hyperglycemia. The condition is linked with particular gut microflora that favor weight gain.

Green tea, consumed widely, is known to have beneficial effects such as reducing body weight and metabolic syndrome. Its components – polyphenols, caffeine (Caf), and L-theanine (Thea), can decrease calorie uptake and stimulate protein kinase.

The components, primarily residing in the large intestine, interact with and modulate the gut microbiome . Research shows green tea extract reduces harmful gut bacteria and increases beneficial ones, potentially impacting obesity.

About the study

The present study prepared green tea using leaves from the Suchazao tea cultivar, sourced from the Zhongshanling tea garden in Nanjing, China. Various concentrations of tea were brewed with distilled water and tested for total tea polyphenols (TPP), Caf, and Thea content via spectrophotometry and high-performance liquid chromatography.

For animal testing, young male C67BL/6J mice were obtained from Yangzhou University, acclimated for a week, and then divided into groups for different dietary regimens.

Some received a HF diet supplemented with green tea infusions, while others were given an HF diet with major green tea components. Mice's water intake and weight were monitored daily.

Study results

The present study examined how green tea affected obesity-related indicators in mice with a HF diet. As anticipated, the mice on this diet gained significant weight and accumulated fat within eight weeks, validating using the HF diet as a model to induce obesity. This contrast in weight gain and fat accumulation was observed against a low-fat (LF) diet group, even though food and water intake had no significant difference for both groups.

However, introducing green tea into the HF diet yielded intriguing results. The study used three different concentrations of green tea in the diet: 1%, 2%, and 4%.

Remarkably, even though the group with the highest concentration of green tea ate more food, they showed the most considerable weight loss and fat reduction, indicating a significant impact of green tea on combating obesity.

Further biochemical tests showed a decline in obesity indicators in green tea mice. Additionally, liver cells from mice on the HF diet plus green tea seemed healthier than those from the pure HF group, providing further evidence of green tea's anti-obesity properties.

Particularly noteworthy was the reduction of inflammation markers tumor necrosis factor-alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) in the groups treated with green tea.

As revealed through NGS, gut microbiota health was also positively impacted by adding green tea. The group consuming the 4% green tea had significant alterations in the population of their intestinal microflora, indicating a potential shift toward a healthier gut environment.

Delving further into the role of TPP, Thea, and Caf in these effects, researchers found that the groups consuming TPP and Thea significantly reduced weight and fat after eight weeks. Furthermore, their liver inflammation was reduced, with TPP having the strongest impact. These components also enhanced intestinal villi length and surface area, improving gut health.

Regarding gut microbiota composition, TPP substantially increased beneficial bacterial populations while decreasing harmful ones. The gut microbiota clusters for Thea and Caf slightly diverged from the HF group, while the TPP cluster was separate from the HF and similar to the LF group.

TPP showed the greatest impact on operational taxonomic units (OTUs), a measure of microbiome diversity. Out of 32 identified obesity-associated microbial genera, each component significantly influenced ten genera.

Conclusions

The researchers found a unique pattern in gut microbiota clustering in mice fed a HF diet supplemented with a green tea. This infusion, particularly at a 4% concentration, substantially improved the intestinal microflora of obese mice, mitigating the metabolic alterations caused by the HF diet.

The study identified 32 genera, including Akkermansia, Saccharofermentans, Acetatifactor, Bacteroides, Alistipes, Allobaculum, and Falsiporphyromonas , as biomarkers associated with the HF diet.

Of these, TPP notably enhanced the presence of Akkermansia , playing a vital role in re-establishing a healthy bacterial community necessary for countering obesity.

Thus, the research suggests that green tea can be a potent remedy for HF diet-induced complications, primarily by modifying gut microbial communities.

Mei, H. et al. (2023) "The Role of Green Tea on the Regulation of Gut Microbes and Prevention of High-Fat Diet-Induced Metabolic Syndrome in Mice", Foods , 12(15), p. 2953. doi: 10.3390/foods12152953 . https://www.mdpi.com/2304-8158/12/15/2953

Tags: Bacteria , Biomarker , Blood , Blood Pressure , Caffeine , Chromatography , Diet , DNA , Food , Gene , Gene Sequencing , Glucose , Green Tea , High Blood Pressure , Hyperglycemia , Inflammation , Kinase , Large Intestine , Liquid Chromatography , Liver , Metabolic Syndrome , Microbiome , Monocyte , Necrosis , Obesity , Protein , Research , Ribonucleic Acid , Small Intestine , Syndrome , Tea , Tumor , Tumor Necrosis Factor , Villi , Weight Loss

Vijay Kumar Malesu

Vijay holds a Ph.D. in Biotechnology and possesses a deep passion for microbiology. His academic journey has allowed him to delve deeper into understanding the intricate world of microorganisms. Through his research and studies, he has gained expertise in various aspects of microbiology, which includes microbial genetics, microbial physiology, and microbial ecology. Vijay has six years of scientific research experience at renowned research institutes such as the Indian Council for Agricultural Research and KIIT University. He has worked on diverse projects in microbiology, biopolymers, and drug delivery. His contributions to these areas have provided him with a comprehensive understanding of the subject matter and the ability to tackle complex research challenges.

Please use one of the following formats to cite this article in your essay, paper or report:

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Kumar Malesu, Vijay. "The green tea effect: From gut microbes to weight loss, new insights emerge". News-Medical . 28 August 2024. <https://www.news-medical.net/news/20230808/The-green-tea-effect-From-gut-microbes-to-weight-loss-new-insights-emerge.aspx>.

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Open access
Published: 06 April 2010

Beneficial effects of green tea: A literature review

Sabu M Chacko 1 ,
Priya T Thambi 1 ,
Ramadasan Kuttan 2 &
Ikuo Nishigaki 1

Chinese Medicine volume 5 , Article number: 13 ( 2010 ) Cite this article

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The health benefits of green tea for a wide variety of ailments, including different types of cancer, heart disease, and liver disease, were reported. Many of these beneficial effects of green tea are related to its catechin, particularly (-)-epigallocatechin-3-gallate, content. There is evidence from in vitro and animal studies on the underlying mechanisms of green tea catechins and their biological actions. There are also human studies on using green tea catechins to treat metabolic syndrome, such as obesity, type II diabetes, and cardiovascular risk factors.

Long-term consumption of tea catechins could be beneficial against high-fat diet-induced obesity and type II diabetes and could reduce the risk of coronary disease. Further research that conforms to international standards should be performed to monitor the pharmacological and clinical effects of green tea and to elucidate its mechanisms of action.

In recent years, the health benefits [ 1 ] of consuming green tea, including the prevention of cancer [ 2 ] and cardiovascular diseases [ 3 ], the anti-inflammatory [ 4 ], antiarthritic [ 5 ], antibacterial [ 6 ], antiangiogenic [ 7 ], antioxidative [ 8 ], antiviral [ 9 ], neuroprotective [ 10 ], and cholesterol-lowering effects [ 11 ] of green tea and isolated green tea constituents are under investigation. However, adding green tea to the diet may cause other serious health concerns.

The health-promoting effects of green tea are mainly attributed to its polyphenol content [ 12 ], particularly flavanols and flavonols, which represent 30% of fresh leaf dry weight [ 1 ]. Recently, many of the aforementioned beneficial effects of green tea were attributed to its most abundant catechin, (-)-epigallocatechin-3-gallate (EGCG) [ 13 – 15 ]. Green tea extracts are more stable than pure epigallocatechin gallate, one of the major constituents of green tea, because of the presence of other antioxidant constituents in the extract [ 8 ]. In general, herbal medicines are complex mixtures of different compounds that often act in a synergistic fashion to exert their full beneficial effect [ 11 ]. However, relatively few herbal medicines have been well characterized and their efficacy demonstrated in systematic clinical trials as compared to Western drugs. This review article highlights the recent research on the efficacy, action mechanisms, and side effects of green tea and its catechins in in vitro , in vivo , and ex vivo systems [ 16 ].

The review on green tea and its catechins focused on language literature in English. The literature search was conducted in the following databases: Pubmed (1980-2009), EMBASE (1980-2009), Allied and complementary Medicine Database (AMED, 1985-2009) and China Journals Full Text Database (1975-2009). The keywords used were selected from the following terms: green tea, catechins, anticancer, diabetes, polyphenols, in vivo studies, general pharmacology and toxicology. The health benefits and adverse effects of green tea and its catechins were reviewed.

The authors read full articles and reached consensus after discussion. Articles included in the study covered the following effects of green tea: (1) the health benefits in humans and animals, (2) absorption of metal ions and drug-metabolizing enzymes, (3) antioxidation and inhibition of oxidative stress, (4) carbohydrate metabolism and diabetes mellitus, and (5) adverse effects. A total of 105 peer-reviewed papers in English were selected for this review.

Tea is one of the most popular beverages consumed worldwide. Tea, from the plant Camellia sinensis , is consumed in different parts of the world as green, black, or Oolong tea. Among all of these, however, the most significant effects on human health have been observed with the consumption of green tea [ 17 ]. The first green tea was exported from India to Japan during the 17th century. It is estimated that about 2.5 million tons of tea leaves are produced each year throughout the world, with 20% produced as green tea, which is mainly consumed in Asia, some parts of North Africa, the United States, and Europe [ 18 ]. The association between tea consumption, especially green tea, and human health has long been appreciated [ 19 , 20 ]. Green tea and black tea are processed differently during manufacturing. To produce green tea, freshly harvested leaves are immediately steamed to prevent fermentation, yielding a dry, stable product. This steaming process destroys the enzymes responsible for breaking down the color pigments in the leaves and allows the tea to maintain its green color during the subsequent rolling and drying processes. These processes preserve natural polyphenols with respect to the health-promoting properties. As green tea is fermented to Oolong and then to black tea, polyphenol compounds (catechins) in green tea are dimerized to form a variety of theaflavins, such that these teas may have different biological activities.

Green tea composition

The chemical composition of green tea is complex: proteins (15-20% dry weight), whose enzymes constitute an important fraction; amino acids (1-4% dry weight) such as theanine or 5- N- ethylglutamine, glutamic acid, tryptophan, glycine, serine, aspartic acid, tyrosine, valine, leucine, threonine, arginine, and lysine; carbohydrates (5-7% dry weight) such as cellulose, pectins, glucose, fructose, and sucrose; minerals and trace elements (5% dry weight) such as calcium, magnesium, chromium, manganese, iron, copper, zinc, molybdenum, selenium, sodium, phosphorus, cobalt, strontium, nickel, potassium, fluorine, and aluminum; and trace amounts of lipids (linoleic and α-linolenic acids), sterols (stigmasterol), vitamins (B, C, E), xanthic bases (caffeine, theophylline), pigments (chlorophyll, carotenoids), and volatile compounds (aldehydes, alcohols, esters, lactones, hydrocarbons). Due to the great importance of the mineral presence in tea, many studies have determined their levels in tea leaves and their infusions (Table 1 ) [ 21 ]. Fresh leaves contain, on average, 3-4% of alkaloids known as methylxanthines, such as caffeine, theobromine, and theophylline [ 22 ]. In addition, there are phenolic acids such as gallic acids and characteristic amino acid such as theanine present [ 22 ].

Green tea contains polyphenols, which include flavanols, flavandiols, flavonoids, and phenolic acids; these compounds may account for up to 30% of the dry weight. Most of the green tea polyphenols (GTPs) are flavonols, commonly known as catechins. Products derived from green tea are mainly extracts of green tea in liquid or powder form that vary in the proportion of polyphenols (45-90%) and caffeine content (0.4-10%). The major flavonoids of green tea are various catechins, which are found in greater amounts in green tea than in black or Oolong tea [ 23 ]. There are four kinds of catechins mainly find in green tea: epicatechin, epigallocatechin, epicatechin-3-gallate, and EGCG [ 24 ]. The preparation methods influence the catechins both quantitatively and qualitatively; the amount of catechins also varies in the original tea leaves due to differences in variety, origin, and growing conditions [ 25 ]. The preparation of fresh green tea cannot totally extract catechins from the leaves; therefore, the concentration found differs from the absolute values determined through the complete extraction of leaves [ 26 ]. Moreover, catechins are relatively unstable and could be quantitatively and qualitatively modified during the time frame of an experiment [ 27 , 28 ]. Thus, comparison of ingested doses in animal studies is not possible because the catechin quantification before administration is often not known.

Health benefits of green tea in humans and animals

Studies using animal models show that green tea catechins provide some protection against degenerative diseases [ 29 ]. Some studies indicated that green tea has an antiproliferative activity on hepatoma cells and a hypolipidemic activity in hepatoma-treated rats, as well as the prevention of hepatoxicity [ 29 ] and as a preventive agent against mammary cancer post-initiation [ 29 ]. Green tea catechins could also act as antitumorigenic agents [ 30 ] and as immune modulators in immunodysfunction caused by transplanted tumors or by carcinogen treatment [ 29 ]. Moreover, green tea, its extract, and its isolated constituents were also found to be effective in preventing oxidative stress [ 31 ] and neurological problems [ 32 ].

Green tea consumption has also been linked to the prevention of many types of cancer, including lung, colon, esophagus, mouth, stomach, small intestine, kidney, pancreas, and mammary glands [ 33 ]. Several epidemiological studies and clinical trials showed that green tea (and black and Oolong teas to a lesser extent) may reduce the risk of many chronic diseases [ 34 ]. This beneficial effect has been attributed to the presence of high amounts of polyphenols, which are potent antioxidants. In particular, green tea may lower blood pressure and thus reduce the risk of stroke and coronary heart disease. Some animal's studies suggested that green tea might protect against the development of coronary heart disease by reducing blood glucose levels and body weight [ 35 ]. However, all these data are based on middle-aged animals' populations, not the elderly populations, which nutritional status tends to be more adversely influenced by age-related biological and socioeconomic factors [ 36 ].

Tea components possess antioxidant, antimutagenic, and anticarcinogenic effects and could protect humans against the risk of cancer by environmental agents [ 37 ]. Sano et al . [ 38 ] reported the inhibitory effects of green tea leaves against tert-butyl hydroperoxide-induced lipid peroxidation, and a similar antioxidant effect on the kidney was observed after oral administration of the major tea polyphenol EGCG. The antioxidative potency of crude catechin powder and individual catechins was tested in experiments using the active oxygen method. Crude catechins reduced the formation of peroxides far more effectively than dl-α-tocopherol [ 39 ]. Shim et al . [ 40 ] studied the chemopreventive effect of green tea among cigarette smokers and found that it can block the cigarette-induced increase in sister chromatid exchange frequency.

The effectiveness of green tea in treating any type of diarrhea and typhoid has been known in Asia since ancient times [ 41 – 43 ]. Green tea catechins have an inhibitory effect on Helicobacter pylori infection [ 44 , 45 ]. Effects of green tea against the influenza virus, especially in its earliest stage, as well as against the Herpes simplex virus have also been demonstrated [ 46 – 48 ]. Furthermore, Weber et al . [ 9 ] observed that adenovirus infection is inhibited in vitro by green tea catechins.

In humans, Hirasawa and Takada [ 49 ] studied the antifungal activity of green tea catechins against Candida albicans and the convenience of a combined treatment with catechins and lower doses of antimycotics, which may help to avoid the side effects of antimycotics. Green tea consumption has also been associated with increased bone mineral density, and it has been identified as an independent factor protecting against the risk of hip fractures; this effect was considered independent of smoking status, hormone replacement therapy, coffee drinking, and the addition of milk to tea [ 50 ]. Park et al . [ 51 ] observed the positive effects of green tea extracts and GTPs on the proliferation and activity of bone cells. The proliferation of hepatic stellate cells is closely related to the progression of liver fibrosis in chronic liver diseases, and EGCG has a potential inhibitory effect on the proliferation of these cells [ 52 , 53 ]. Green tea strengthens the immune system action because it protects it against oxidants and radicals. Recent studies suggested that GTPs might protect against Parkinson's and Alzheimer's diseases and other neurodegenerative diseases [ 10 , 54 ]. Studies have demonstrated GTP neuroprotectant activity in cell cultures and animal models, such as the prevention of neurotoxin-induced cell injury [ 54 ]. Green tea is considered to be useful for insect stings due mainly to its anti-inflammatory effects and its capacity to stop bleeding [ 55 , 56 ]. Some studies have suggested an inverse association between green tea consumption and the risk of kidney stone formation [ 41 , 57 ]. In an experimental cataractogenesis system, green tea acted by preserving the antioxidant defense system of the lens [ 58 ]. Skrzydlewska et al . [ 59 ] indicated a beneficial effect of green tea in alcohol intoxication. In addition to all of these reported properties, which have helped the recognition of green tea as functional food by some authors [ 60 ], green tea is also currently used in the preparation of a variety of foods, pharmaceutical preparations, dentifrices, and cosmetics [ 61 ].

Tea has been shown anticarcinogenic effects against breast cancer in experimental studies [ 62 ]. However, epidemiologic evidence that tea protects against breast cancer has been inconsistent [ 62 ]. A case-control study was conducted in southeastern China between 2004 and 2005 [ 63 ]. The incidence cases were 1009 female patients aged 20-87 years with histologically confirmed breast cancer, and the 1009 age-matched controls were healthy women randomly recruited from breast disease clinics. Information on duration, frequency, quantity, preparation, and type of tea consumption as well as diet and lifestyle were collected by face-to-face interviews using a validated and reliable questionnaire. In comparison with non-tea drinkers, green tea drinkers tended to reside in urban settings, to have more education, and to consume more coffee, alcohol, soy, vegetables, and fruits. After adjusting established and potential confounding factors, green tea consumption was associated with a reduced risk of breast cancer. Similar dose-response relationships were observed for duration of drinking green tea, number of cups consumed, and new batches prepared per day.

Hsu et al . [ 64 ] demonstrated the effects of supplementation with decaffeinated green tea extract (catechins) on hemodialysis-induced reactive oxygen species, atherosclerotic disease risk factors, and proinflammatory cytokines. The pharmacokinetics of one oral dose of catechins was compared between healthy subjects and hemodialysis patients. The authors compared the antioxidant effects of three different doses (0, 455, and 910 mg) of oral catechins with that of oral vitamin C (500 mg) during a hemodialysis session. In patients, catechin supplementation reduced hemodialysis-enhanced plasma hypochlorous acid activity more effectively than did placebo or vitamin C. Between the treatments with 455 and 910 mg catechins, no significant difference was found in the reduction of plasma hypochlorous acid activity. Catechins also significantly reduced proinflammatory cytokine expression enhanced by hemodialysis.

Effects on absorption of metal ions

Tea catechins can affect iron absorption, particularly in groups at risk of iron deficiency [ 65 , 66 ], but their effects on other ions are poorly understood. Green tea ingestion over a long period does not affect the apparent absorption of copper, whereas it decreases that of zinc and increases that of manganese [ 67 ]. However, catechin intake does not affect the plasma concentration of these ions [ 68 ]. Green tea catechins have the potential to affect absorption and metabolism of ions because flavonoids interact with a variety of metal ions [ 69 ].

Effects on drug-metabolizing enzymes

Long-term ingestion of green tea increases UDP-glucuronosyl transferase activity in rats [ 66 , 70 , 71 ], and after being absorbed, catechins are metabolized by drug-metabolizing enzymes in various organs [ 72 , 73 ]. Thus, the increased glucuronidation through UDP-glucuronosyl transferase induction is postulated to contribute to the anticarcinogenic effect of green tea by facilitating the metabolism of chemical carcinogens into inactive products that are readily excreted. The interaction between 2-amino-3-methylimidazol (4,5-f)quinoline (IQ) and green tea catechin metabolism was examined [ 74 ]. IQ is a precarcinogen that was originally detected in an extract of fried meat. The major route of IQ biotransformation in rats is cytochrome P450 in the first step, followed by conjugation to a sulfate and a glucuronide conjugate. Green tea modifies IQ metabolism in rats, increasing the formation of IQ glucuronides, which are then excreted in the urine. Moreover, protection against cancers induced by polycyclic aromatic hydrocarbons by green tea catechins may be due to the inhibition of their cytochrome P450 metabolism, but the effect of green tea on cytochrome P450 enzymes depends on the particular form. The long-term consumption of green tea increases cytochrome P450 1A1 and 1A2 activities, but not 2B1 and 2E1 activities, in normal rats. However, it is difficult to draw conclusions about a beneficial effect of green tea against carcinogens involving only modulation of this metabolic pathway.

Effects on antioxidant markers and oxidative stress

Green tea is a popular neutraceutical as an antioxidant. Antioxidants are compounds that protect cells against the damaging effects of reactive oxygen species, such as singlet oxygen, superoxide, peroxyl radicals, hydroxyl radicals, and peroxynitrite. An imbalance between antioxidants and reactive oxygen species results in oxidative stress, leading to cellular damage [ 75 ]. Catechins are hypothesized to help protect against these diseases by contributing, along with antioxidant vitamins (i.e., vitamins C and E) and enzymes (i.e., superoxide dismutase and catalase), to the total antioxidant defense system [ 76 ].

In vivo studies showed that green tea catechins increase total plasma antioxidant activity [ 77 , 78 ]. Intake of green tea extracts also increases the activity of superoxide dismutase in serum and the expression of catalase in the aorta; these enzymes are implicated in cellular protection against reactive oxygen species [ 78 , 79 ]. This action is combined with direct action on oxygen species by a decrease in the nitric oxide plasma concentration [ 80 ]. Malondialdehyde, a marker of oxidative stress, also decreases after green tea intake [ 77 , 80 ]. These results suggest that catechins could have a direct (antioxidant) or indirect (increase of activity or expression) effect. Since catechins can act as antioxidants in vitro , they might prevent the oxidation of other antioxidants, such as vitamin E. However, ingestion of green tea catechins does not modify the plasma status of vitamins E and C in vivo [ 78 , 81 , 82 ]. Nevertheless, one study reported that catechins increase vitamin E concentration in low-density lipoprotein [ 81 ] and in this way could protect low-density lipoprotein against peroxidation [ 77 ].

Pilipenko et al . [ 83 ] assessed the tolerance of tableted green tea and its effect on the antioxidant status indices. Twenty-five patients with different gastrointestinal pathologies were included in the study and divided into treatment and control groups. The tolerance of tableted green tea was good in the treatment group, who showed better dynamics of quality-of-life indices, especially in scales of body pain and social functioning. There were no significant differences in biochemical analysis between the groups, which may indicate the safety of this product. Analysis revealed that the treatment group showed a decreased level of all antioxidant status indices, as reflected in a significant decreasing of the lipid peroxidation index from 4.63 to 4.14.

Effects on carbohydrate metabolism

Type II diabetes is a heterogeneous disorder that involves resistance of glucose and lipid metabolism in peripheral tissues to the biological activity of insulin and inadequate insulin secretion by pancreatic β cells [ 84 ]. Animal models of diabetes are available: Zucker rats, which are genetically obese; injection of streptozotocin or alloxan, which destroys pancreatic β cells; and treatment with sucrose-rich diets, which induces obesity and insulin resistance.

In a study by Sabu et al . [ 85 ], administration of GTPs (500 mg/kg) to normal rats increased glucose tolerance significantly at 60 minutes. GTPs were also found to reduce significantly serum glucose levels in alloxan diabetic rats at a dose of 100 mg/kg. Continued daily administration (15 days) of the extract at 50 or 100 mg/kg produced 29% and 44% reduction, respectively, in the elevated serum glucose level produced by alloxan administration. Elevated hepatic and renal enzymes produced by alloxan were found to be reduced significantly by GTPs. The serum lipid peroxidation level was increased by alloxan and reduced significantly by the administration of 100 mg/kg of GTPs. Decreased liver glycogen resulting from alloxan administration showed a significant increase after GTP treatment. The GTP-treated group showed increased antioxidant potential, as seen from improvements in superoxide dismutase and glutathione levels. However, catalase, lipid peroxidation, and glutathione peroxidase levels were unchanged. These results indicate that alterations in the glucose utilizing system and oxidation status in rats that were increased by alloxan were partially reversed by the administration of GTPs [ 85 ].

Catechins also reduced plasma triglyceride levels in an oral glucose-tolerance test in normal rats [ 86 ]. Green tea extract intake reduced these values in both Zucker rats and rats fed a sucrose-rich diet [ 87 , 88 ]. Several human- and animal-based studies suggested that green tea and its flavonoids have antidiabetic effects [ 86 , 89 , 90 ]. Green tea flavonoids were also shown to have insulin-like activities [ 91 ] as well as insulin-enhancing activity [ 92 ].

The antihyperglycemic effect of black tea was reported by Gomes et al . [ 93 ]. EGCG was found to inhibit intestinal glucose uptake by the sodium-dependent glucose transporter SGLT1, indicating its increase in controlling blood sugar [ 94 ]. Streptozotocin diabetic rats showed increased sensitivity to platelet aggregation and thrombosis, and this abnormality could be improved by dietary catechins from green tea [ 95 , 96 ]. Alloxan produces oxygen radicals in the body, which cause pancreatic injury [ 75 ] and are responsible for increased blood sugar.

Under in vivo conditions, glutathione acts as an antioxidant, and its decrease was reported in a diabetes mellitus model [ 97 ]. The increased glutathione content in the liver of the rats treated with GTPs may be one of the factors responsible for the inhibition of lipid peroxidation. Superoxide dismutase and catalase are the two major scavenging enzymes that remove the toxic free radicals in vivo . Vucic et al . [ 98 ] reported that the activity of superoxide dismutase is low in diabetes mellitus.

The Mediterranean Islands (MEDIS) epidemiological study is a cross-sectional health and nutrition survey that aims to evaluate the association between various sociodemographic, bioclinical, dietary, and other lifestyle habits and the prevalence of the common cardiovascular disease risk factors (i.e., hypertension, dyslipidemia, diabetes, and obesity) among elderly people without a history of any chronic disease and living in the Mediterranean islands. Because data relating tea consumption with clinical characteristics are lacking in elderly populations, in the context of the MEDIS study, the authors sought to evaluate whether green tea consumption is independently associated with fasting blood glucose levels and the prevalence of type II diabetes mellitus [ 99 ]. An earlier study was aimed at providing evidence of improvement in glucose metabolism in diabetic mice and healthy humans upon green tea consumption [ 35 ]. Green tea promoted glucose metabolism in healthy human volunteers at 1.5 g/kg as shown in oral glucose-tolerance tests. Green tea also lowered blood glucose levels in diabetic db+/db+ mice and streptozotocin-diabetic mice two to six hours after administration at 300 mg/kg without affecting serum insulin level, whereas no effect was observed in control mice (+m/+m and normal ddY mice).

Effect of EGCG on diabetes

A study by Waltner-Law et al . [ 91 ] provided compelling in vitro evidence that EGCG decreases glucose production of H4IIE rat hepatoma cells. The investigators showed that EGCG mimics insulin, increases tyrosine phosphorylation of the insulin receptor and the insulin receptor substrate, and reduces gene expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase. Recently, green tea and green tea extracts were demonstrated to modify glucose metabolism beneficially in experimental models of type II diabetes mellitus [ 35 , 100 ]. In addition, EGCG ameliorates cytokine-induced β cell damage in vitro [ 101 ] and prevents the decrease of islet mass induced by treatment with multiple low doses of streptozotocin in vivo [ 102 ].

Lambert et al . [ 103 ] showed that intragastric administration of EGCG at a dose of 75 mg/kg resulted in a Cmax of 128 mg/l total plasma EGCG and a terminal half-life of 83 minutes. Furthermore, in humans an oral intake of EGCG at a dose of 50 mg (0.7 mg/kg) resulted in a Cmax of 130 mg/l total plasma EGCG and a terminal half-life of 112 minutes [ 104 ]. These results indicate that rodents must be orally administered 100- to 600-fold more EGCG (depending on whether they are administered by gavage or by feed admixture) to achieve similar plasma concentrations as those found in humans. Total plasma EGCG concentrations shown to be efficacious in mice and rats can be reached by an intake of low to moderate doses of EGCG in humans.

Effect on obesity

The effects of tea on obesity and diabetes have received increasing attention. Tea catechins, especially EGCG, appear to have antiobesity and antidiabetic effects [ 105 ]. African black tea extract has been shown to suppress the elevation of blood glucose during food intake and reduce the body weight in KK-A(y)/TaJcl diabetic mice [ 106 ]. Although few epidemiological and clinical studies have shown the health benefits of EGCG on obesity and diabetes, the mechanisms of its actions are emerging based on various laboratory data. These mechanisms may be related to certain pathways, such as through the modulations of energy balance, endocrine systems, food intake, lipid and carbohydrate metabolism, and redox status [ 88 ].

A double-blind, placebo-controlled, cross-over design study showed that consumption of a beverage containing green tea catechins, caffeine, and calcium increases 24-h energy expenditure by 4.6%, but the contribution of the individual ingredients could not be distinguished. It was suggested that such modifications were sufficient to prevent weight gain. It has been reported that the body weights of rats and their plasma triglyceride, cholesterol, and low-density lipoprotein cholesterol were significantly reduced by feedings of Oolong, black, and green tea leaves to the animals. In addition, the inhibition of growth and suppression of lipogenesis in MCF-7 breast cancer cells may be through down-regulation of fatty acid synthase gene expression in the nucleus and stimulation of cell energy expenditure in the mitochondria [ 107 , 108 ]. When fed to mice, EGCG purified from green tea decreased diet-induced obesity in mice by decreasing energy absorption and increasing fat oxidation [ 109 ]. The increased and prolonged sympathetic stimulation of thermogenesis by the interaction between polyphenols and caffeine could be of value in assisting the management of obesity [ 110 ].

Recent data from human studies indicate that the consumption of green tea and green tea extracts may help reduce body weight, mainly body fat, by increasing postprandial thermogenesis and fat oxidation. In a randomized, double-blind, placebo-controlled, cross-over pilot study, six overweight men were given 300 mg EGCG per day for two days. Fasting and postprandial changes in energy expenditure and substrate oxidation were assessed. Resting energy expenditure did not differ significantly between EGCG and placebo treatments, although during the first postprandial monitoring phase, respiratory quotient values were significantly lower with EGCG treatment compared to the placebo. These findings suggest that EGCG alone has the potential to increase fat oxidation in men and may thereby contribute to the antiobesity effects of green tea. However, more studies with a greater sample size and a broader range of age and body mass index are needed to define the optimal dose [ 111 ].

Adverse effects of green tea

Although green tea has several beneficial effects on health, the effects of green tea and its constituents may be beneficial up to a certain dose yet higher doses may cause some unknown adverse effects. Moreover, the effects of green tea catechins may not be similar in all individuals. EGCG of green tea extract is cytotoxic, and higher consumption of green tea can exert acute cytotoxicity in liver cells, a major metabolic organ in the body [ 112 ]. Another study found that higher intake of green tea might cause oxidative DNA damage of hamster pancreas and liver [ 113 ]. Yun et al . [ 114 ] clarified that EGCG acts as a pro-oxidant, rather than an antioxidant, in pancreatic β cells in vivo . Therefore, high intake of green tea may be detrimental for diabetic animals to control hyperglycemia. At a high dose (5% of diet for 13 wk), green tea extract induced a thyroid enlargement (goiter) in normal rats [ 115 , 116 ]. This high-level treatment modified the plasma concentrations of the thyroid hormones. However, drinking even a very high dietary amount of green tea would be unlikely to cause these adverse effects in humans.

Harmful effects of tea overconsumption (black or green) are due to three main factors: (1) its caffeine content, (2) the presence of aluminum, and (3) the effects of tea polyphenols on iron bioavailability. Green tea should not be taken by patients suffering from heart conditions or major cardiovascular problems. Pregnant and breast-feeding women should drink no more than one or two cups per day, because caffeine can cause an increase in heart rhythm. It is also important to control the concomitant consumption of green tea and some drugs, due to caffeine's diuretic effects [ 117 ]. Some studies revealed the capacity of tea plants to accumulate high levels of aluminum. This aspect is important for patients with renal failure because aluminum can be accumulated by the body, resulting in neurological diseases; it is therefore necessary to control the intake of food with high amounts of this metal [ 118 ]. Likewise, green tea catechins may have an affinity for iron, and green tea infusions can cause a significant decrease of the iron bioavailability from the diet [ 119 ].

Conclusions

Laboratory studies showed the health effects of green tea. As the human clinical evidence is still limited, future research needs to define the actual magnitude of health benefits, establishes the safe range of tea consumption associated with these benefits, and elucidates the mechanisms of action. Development of more specific and sensitive methods with more representative models along with the development of good predictive biomarkers will give a better understanding of how green tea interacts with endogenous systems and other exogenous factors. Definitive conclusions concerning the protective effect of green tea have to come from well-designed observational epidemiological studies and intervention trials. The development of biomarkers for green tea consumption, as well as molecular markers for its biological effects, will facilitate future research in this area.

Abbreviations

epigallocatechin-3-gallate

green tea polyphenols

Uridine di-phospatase

2-amino-3-methylimidazol (4,5-f)quinoline

Mediterranean Islands

Sodium dependent glucose transporter

Allied and complementary Medicine Database.

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Chacko, S.M., Thambi, P.T., Kuttan, R. et al. Beneficial effects of green tea: A literature review. Chin Med 5 , 13 (2010). https://doi.org/10.1186/1749-8546-5-13

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Turmeric and green tea among health supplements putting people in hospital

More than 15 million Americans may be putting their liver health at risk, simply by trying to better their overall health. New research has revealed the extent of the damage being caused by taking popular botanical supplements including turmeric, green tea, the stress-relieving ashwagandha and weight-loss aid Garcinia cambogia.

Health researchers from the University of Michigan, Ann Arbor, looked at data from 2017 to 2021, covering 9,685 people, and found that nearly 4.7% of US adults had used one of the six potentially toxic supplements within the previous 30 days. Those supplements were turmeric, green tea, ashwagandha, G. cambogia, black cohosh and red yeast rice.

Supplement users were mostly taking these botanicals of their own accord, not due to medical directives, for a range of issues: turmeric for joint health and arthritis, green tea extract to boost energy levels, G. cambogia for weight loss, black cohosh to manage hot flushes and red yeast rice for heart health. We should add that when the study talks of green tea, it's specifically concerned with green tea extract , not drinking tea (which has no link to liver toxicity – though a limit of eight cups a day is recommended).

And while news of liver toxicity connected to these supplements is not new, having been reported to be on the rise for some time now, including in this 2022 study , medical researchers are concerned that people are unaware that they come with a serious risk of overdose that results in emergency department presentations. Hospitalizations increased from 7% to 20% over the decade between 2004 and 2014.

"Use of herbal and dietary supplements (HDSs) accounts for an increasing proportion of drug hepatotoxicity cases," said the researchers, led by Alisa Likhitsup, an assistant professor of gastroenterology.

Drug-induced hepatotoxicity is an acute or chronic liver injury also known as toxic liver disease, with a host of symptoms including yellowing of the skin, fatigue, nausea, rash, itching and upper-right abdominal pain. While it can be treated by removing the toxic trigger, it can lead to serious consequences, including the patient needing a liver transplant or even dying from it if it is untreated or missed.

While hospitalizations due to misuse of herbal supplements are on the rise, the researchers are not campaigning for abstinence, but for users to be vigilant with ingredients and dosages, especially if they're taking a combination of them or other medicines to treat chronic conditions.

"In light of the lack of regulatory oversight on the manufacturing and testing of botanical products, it is recommended that clinicians obtain a full medication and HDS use history when evaluating patients with unexplained symptoms or liver test abnormalities," they wrote in the study. "Considering widespread and growing popularity of botanical products, we urge government authorities to consider increasing the regulatory oversight on how botanicals are produced, marketed, tested, and monitored in the general population."

They also point out that the regulatory processes surrounding these supplements are not as stringent as for prescription medicines, and that chemical testing of products has revealed inconsistencies between what's advertised on the bottle and what dose is in a tablet.

What's more, clinical trials into the efficacy of these supplements have not provided robust evidence of their benefits compared to their risks when they're taken at higher doses. Safe amounts of each supplement of course depends on any prescription medicines an individual may be taking, as well as their baseline liver health and other medical conditions. As such, recommendations of safe doses should ideally be personalized.

"The safety and efficacy of HDSs are not well established due to the lack of regulatory requirements by the US Food and Drug Administration for human pharmacokinetic or prospective clinical trials prior to marketing," the researchers added.

In 2023, the Australian FDA equivalent, the Therapeutic Goods Association (TGA), issued a warning that highlighted the risk of liver injury from consuming turmeric and/or curcumin. While they cautioned that serious injury is rare, the risk varied depending on an individual's bioabsorption and liver health.

"The risk of liver injury does not appear to relate to Curcuma longa (turmeric) when consumed in typical dietary amounts as a food," the TGA added, offering a pinch of good news for those who cook with the popular orange spice.

The study was published in the journal JAMA Network Open .

Source: University of Michigan via Medical Xpress

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Matcha 101: benefits, caffeine content, side effects & recipe ideas.

Matcha has taken the world by storm in recent years, captivating tea enthusiasts and health-conscious individuals alike. But what exactly is matcha, and what makes it so special?

We chatted with health experts and dietitians specializing in Japanese cooking to get the scoop on the benefits of matcha and how to prepare this vibrant tea at home.

What is matcha?

Matcha is a type of powdered green tea from Japan that continues to gain popularity worldwide. What sets matcha apart is its distinctive cultivation and preparation process.

Matcha tea plants are shaded from excessive sunlight using bamboo mats during the growth period. This traditional growing method produces plants that are higher in theanine, antioxidants, chlorophyll, and caffeine 1 than other green teas.

Unlike other tea processes where the leaves are steeped and discarded, matcha involves finely grinding shade-grown green tea leaves into a bright green powder. Traditionally, matcha is whisked with a small amount of hot water and served in a bowl to be enjoyed in its pure form.

Matcha's distinct flavor also sets it apart from other teas. While some would describe the taste as grassy and bitter, high-quality matcha prepared correctly will be high in umami and have a slight sweetness.

“In Japan, we say, 'enjoy the taste of green tea, but enjoy the aroma of other tea, such as black tea,'" says registered dietitian Asako Miyashita, MS, RDN, CDN . Miyashita notes that brewing matcha slowly at a low temperature is the secret to a delicious cup.

Caffeine content of matcha

A typical cup of matcha has around 30-40 milligrams of caffeine, though it can contain far more depending on the brand.

“Matcha has higher caffeine than other green teas. Depending on the type and brand of matcha, one cup might even have more caffeine than the same amount of coffee, ” explains dietitian and chef Cindy Chou, RDN .

But matcha also contains the amino acid L-theanine , which helps provides a more balanced energy boost. This is why many people notice the caffeine feels more mild than the caffeine in other teas or coffee. Some Japanese dietitians sip on matcha throughout the day, even after dinner, to help calm their minds before bed.

Here’s how the caffeine content of matcha stacks up against coffee and other teas, according to USDA data. Keep in mind that the exact caffeine content will vary depending on the brand and serving size.

Drink	Caffeine per cup
Japanese matcha	30-40 mg
Green tea	29.4 mg
Black tea	47.4 mg
Coffee	91.8 mg

Benefits of matcha

Matcha is renowned for its high concentration of antioxidants, notably catechins 1 , which are believed to have various health benefits, including potential cancer-fighting properties and improving metabolic health.

Additionally, matcha contains L-theanine, an amino acid that promotes relaxation and mental alertness 2 , providing a calm and focused energy boost .

Due to its potential for preventing many diseases and supporting cognitive function, regular matcha consumption may positively affect both physical and mental health. Here are its most promising health benefits.

It's high in antioxidants.

Green teas, like matcha, contain a considerable amount of catechins, the most abundant being epigallocatechin gallate (EGCG), a group of flavonoids with antioxidant and anti-inflammatory properties 3 . The high polyphenolic content of matcha is better at scavenging free radicals than vitamin C on its own 1 .

“Matcha is particularly high in a type of antioxidant called polyphenols 1 , which have been shown to have many health benefits themselves,” says dietitian Jennifer Akimoto, MAN, RD . “The benefits of matcha may be more of the synergistic effects 4 of several different compounds, including caffeine and vitamin C, theanine, and chlorophyll."

It may enhance cognitive function.

“Many studies showing health benefits are from green tea and not specific to matcha. However, there have been some small studies examining the benefits of matcha on brain function 5 ,” says Akimoto. “Theanine, in combination with caffeine, has been found to improve attention and reaction rates in older adults 6 .”

Matcha improves cognitive function 4 both in the short and long term because the theanine in matcha promotes a calm nervous system, explains William Siff, L.Ac MscAOM , acupuncturist and clinical herbalist.

“Its moderate caffeine content helps to amplify the cognitive effects of the theanine 4 , and the two together create a unique, balanced state of mind that is both alert and relaxed," Siff adds. "The compounds in matcha help to improve clarity, reduce anxiety, and improve memory and focus 4 .”

It may have cardioprotective effects.

The EGCG and rutin in matcha green tea have been associated with cardioprotective properties 1 . EGCG may reduce oxidative stress and prevent the activation of certain proteins and signaling pathways that trigger inflammation in our body. When interacting synergistically with vitamin C, rutin is a potent antioxidant that may strengthen blood vessels 7 .

“Studies have shown that drinking green tea on a daily basis may help to reduce the risk of cardiovascular disease 8 , with EGCG potentially lowering LDL-cholesterol levels 8 .” says Chou. “Though, more research is needed.”

It may have anticancer properties.

Phenolic acids, like those found in matcha, have high antioxidant and anti-inflammatory potential, which may inhibit cancer cell growth and prevent metastasis 1 .

EGCG in green teas, like matcha, seems to have some special abilities that could help fight against cancer 9 by preventing the growth of blood vessels that feed tumors, protecting our cells from damage, and reducing the risk of cancer-causing processes. Consuming large amounts of EGCG may reduce the incidence of colorectal and biliary duct cancers 1 and inhibit the growth and proliferation of gallbladder and bile duct cancer cells.

It may support metabolism.

Some phenolic acids found in matcha can help control how our bodies digest and absorb fats and carbohydrates, which may offer support in managing metabolic 1 conditions 1 . Matcha may also help lower blood glucose levels and improve insulin sensitivity.

In a small study of adult females, consuming matcha daily for three weeks enhanced exercise-induced fat oxidation 10 during a 30-minute brisk walk.

Studies have shown that green tea extracts can reduce body weight and waist circumference 11 when combined with a balanced diet and regular physical exercise. While most studies showing metabolic benefits are from green tea and not specific to matcha, they do come from the same plant and contain similar compounds.

Matcha side effects

As with most things, matcha does have some potential downsides to consider.

“If you consume matcha on an empty stomach, it can be irritating or cause some queasiness,” says Siff. “It’s traditionally served with little mochi sweets in Japan for that reason. Accompany your matcha with something small to eat to offset its astringency and bitterness.”

Siff adds that lower-quality matcha tends to have a higher tannin content and lower L-theanine content, making it more likely to upset or overstimulate the stomach. (We're sharing tips on buying a high-quality powder below.)

Miyashita points out that matcha also contains tannins, which may cause dizziness or interfere with iron absorption 12 , and oxalates, which can trigger or contribute to kidney stones 13 in some people who are more sensitive to oxalates.

How to make matcha

With the right tools, matcha tea is very easy to make at home.

“Traditionally, matcha is made using a bamboo whisk, called a chasen . It adds air to your matcha and creates a lovely foam and froth,” explains Akimoto. If you don't have a chasen, you can use a mason jar, Akimoto adds. Simply add a small amount of water to the jar, followed by your matcha powder, close the jar, and shake.

“Matcha tends to clump when it comes into contact with liquids, so it’ll help to sift it with a fine mesh strainer before mixing,” says Chou. Traditionally, matcha is served without any sugar or milk.

Matcha latte recipe

Courtesy of Asako Miyashita, MS, RDN, CDN

Serving size 1

Ingredients

1.5-2 teaspoons (3-4 grams) of matcha powder
30-40 milliliters water in 80-90℃ (176-194°F) temperature
200-250 milliliters of milk/plant-based milk
Optional: your favorite sweetener/spice/matcha powder as topping
Measure matcha powder and sift it into a tea bowl using a tea strainer. The tea strainer helps get rid of clumps.
Add boiled water and cool it to 80-90℃ (176-194°F). Pour 30-40ml of hot water into matcha in the tea bowl.
Whisk the tea until you don't see any clumps. A bamboo whisk is better, but use a spoon or frother if you don't have it. If you still see clumps, strain the tea one more time with the tea strainer.
Warm the milk and fill the tea bowl with the milk - use a milk frother or whisk to combine. If you do not have a frother or whisk but still want to form milk, shake the milk in a container with a lid, and then add it to matcha)

Other ways to drink matcha

Once you have this basic preparation down, here are a few creative more ways to serve your matcha.

Hold a traditional Japanese tea ceremony

Functional nutrition expert Michiko Tomioka, RDN, IFNCP , has been seriously practicing chado (traditional Japanese tea ceremony) for years. One thing she wants people to understand about matcha is that it’s not just a tea, but a way of living.

Chado says that serving matcha to others is a way to promote hospitality between a host and their guest. So while you can make a matcha latte with a blender, Tomioka says taking the time to prepare matcha with the proper bamboo whisk gives the host a moment of calm and the privilege of enjoying the aroma of matcha while preparing it for their guest.

The traditional way of preparing matcha enhances flavor, umami, and fragrance.

Use it for smoothies and lattes

Straight matcha can be an acquired taste, which is why many people add milk and sweeteners to create creamy drinks like lattes and smoothies that offset some of the bitterness of the matcha.

“If you don’t have a whisk or frother, you can use a blender on lower speeds to mix sifted matcha with water first, then add your choice of milk to make a latte,” says Chou.

Add it to baked goods

You can also add its flavor and characteristic green color to pastries, cookies, loaves, and other baked goods. Akimoto says its umami flavor is a nice addition to desserts because it's not too sweet.

"In baked goods, coconut milk pairs especially well with the umami and slight bitterness of matcha," says Chou.

Sip it iced

“Pure, whisked matcha is great over ice," Siff says. "It’s also nice to add lemon or lime juice to an iced matcha, along with a preferred natural sweetener. This preparation really enhances the fresh, lighter, uplifting qualities of matcha."

He notes that you can also add a citrus-flavored electrolyte powder to your iced matcha for extra hydration.

Enhance its nutrition with a greens powder

"To enhance the nutrient profile, you can add moringa or ashitaba powder to your matcha," says Siff. "This works for hot, iced, and latte formats.” He suggests using a ratio of ⅔ matcha to ⅓ greens powder.

How to buy matcha

When shopping for matcha powder, you’ll typically see ceremonial or culinary-grade matcha.

“Ceremonial-grade matcha is meant to be enjoyed on its own. Culinary-grade matcha can be paired with different plant-based milks and sweeteners,” says Chou.

While more expensive, ceremonial-grade matcha from Japan is the highest quality and provides a distinct flavor that is not bitter.

Culinary-grade matcha still has many of the same health benefits, but it tends to taste more bitter and isn't as pleasant for daily drinking.

When shopping for matcha, look for products that are organic or use a designation on their label that they are grown without chemicals.

Frequently Asked Questions

Are there side effects of drinking matcha.

People who are sensitive to caffeine may experience side effects like jitters, anxiety, faster heart rate, nausea, headache, and even insomnia if they consume too much matcha. Matcha tends to be higher in caffeine than other green teas, but lower in caffeine than coffee.

How often should you drink matcha?

For healthy adults, drinking 1-2 cups of matcha (up to 2 teaspoons of matcha powder) every day is likely safe.

Does matcha speed up metabolism?

Most studies showing metabolic benefits are from green tea and not matcha specifically, but they come from the same plant and contain similar compounds, so possibly. More research is needed in this area.

The takeaway

Matcha is a powerful beverage with a rich history. Rich in antioxidants, matcha may support metabolic health, cognitive function, and more.

Whether you prefer ceremonial-grade matcha for its pure taste or culinary-grade matcha for creative kitchen delights, incorporating matcha into your daily routine can be as tasty as it is healthy. Check out some other top teas for well-being here .

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Popular health supplements causing liver damage, hospitalizations, research finds

Published: Aug. 08, 2024, 2:06 p.m.

Turmeric is one of six supplements causing health issues requiring hospitalization, researchers have found. (Getty Images) Getty Images

Ann Marie Barron | [email protected]

STATEN ISLAND, N.Y. — Popular supplements used by more than 15 million Americans may be putting their liver health at risk, according to health researchers.

Research has revealed the extent of the damage being caused by taking popular botanical supplements including turmeric, green tea, the stress-relieving ashwagandha and weight-loss aid Garcinia cambogia.

For this most recent study, University of Michigan health researchers in Ann Arbor looked at data from 2017 to 2021, covering 9,685 people, and found that nearly 4.7% of U.S. adults had used one of the six potentially toxic supplements within the previous 30 days. The resulting paper, “Estimated Exposure to 6 Potentially Hepatoxic Botanicals in U.S. Adults,” appeared in JAMA Network Open this month .

Supplement users were mostly taking these botanicals on their own, not under medical advice, for a range of issues: Turmeric is taken for joint health and arthritis, green tea extract is thought to boost energy levels, G. cambogia is taken for weight loss, black cohosh is taken to manage hot flushes and red yeast rice is taken for heart health.

The study was specifically concerned with green tea extract, not drinking tea, which has no link to liver toxicity – though a limit of eight cups a day is recommended, according to a report in New Atlas, a science and technology publication.

Hospitalizations increased from 7% to 20% over the decade between 2004 and 2014, the new study found.

“Use of herbal and dietary supplements (HDSs) accounts for an increasing proportion of drug hepatotoxicity cases,” researchers, led by Alisa Likhitsup, an assistant professor of gastroenterology, told New Atlas

Drug-induced hepatotoxicity is an acute or chronic liver injury also known as toxic liver disease, with a host of symptoms including yellowing of the skin, fatigue, nausea, rash, itching and upper-right abdominal pain, according to the National Library of Medicine. And, while it can be treated by removing the toxic trigger, it can lead to serious consequences — including the patient needing a liver transplant or even death if it is left untreated.

The researchers are not campaigning for abstinence, but urge users to be vigilant with ingredients and dosages, especially if they’re taking a combination of them or other medications, according to the report.

“In light of the lack of regulatory oversight on the manufacturing and testing of botanical products, it is recommended that clinicians obtain a full medication and HDS use history when evaluating patients with unexplained symptoms or liver test abnormalities,” they wrote in the study. “Considering widespread and growing popularity of botanical products, we urge government authorities to consider increasing the regulatory oversight on how botanicals are produced, marketed, tested, and monitored in the general population.”

‘A coin flip’

Regulatory processes surrounding these supplements are not as stringent as for prescription medicines, and chemical testing of products has revealed inconsistencies between what’s advertised on the bottle and what dose is in a tablet, researchers reported.

“In a previous study, we found that there was a great deal of mislabeling of some of these products,” said Dr. Robert Fontana, a Michigan Medicine a hepatologist, professor of medicine and the study’s senior author.

“We performed analytical chemistry and found about a 50% mismatch between stated ingredients on the label and what they actually contained, which is quite alarming,’' Fontana said. “If you buy a supplement and it says it has a certain ingredient, it’s basically a coin flip if that’s true or not.”

In the studied population, the highest proportion of people consumed turmeric (3.46%), followed by green tea (1.01%), ashwagandha and black cohosh (0.38%), garcinia cambogia (0.27%), and red yeast rice products (0.19%), researchers reported.

And clinical trials into the efficacy of these supplements have not provided robust evidence of their benefits compared to their risks when they’re taken at higher doses, the researchers reported.

Safe amounts of each supplement depends on any prescription medicines an individual may be taking, as well as their baseline liver health and other medical conditions.

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NEWS FEATURE
20 August 2024

How ‘green’ electricity from wood harms the planet — and people

Melba Newsome 0

Melba Newsome is a freelance journalist in Charlotte, North Carolina.

You can also search for this author in PubMed Google Scholar

A truck takes wood to an Enviva wood-pellet plant in Garysburg, North Carolina. Credit: Mehmet Demirci/Redux/eyevine

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The town of Hamlet, North Carolina, seemed to hit the jackpot in September 2014. After the community had endured decades of economic despair and high poverty rates, the world’s largest producer of wood-based energy, Enviva Biomass, announced plans to open a major facility nearby that would turn wood into dense pellets that can be used as fuel. The project promised 80 well-paying jobs for residents in Hamlet and the surrounding area. It seemed like a win for both local people and the planet.

The company’s plant, which opened in 2019, is part of a global expansion in the use of wood — or solid biomass — to generate electricity. Pellet companies advertise their products as a renewable-energy source that lowers carbon emissions, and the European Union agrees, which has spurred many countries, including the United Kingdom, Belgium and Denmark, to embrace this form of energy. As with similar projects worldwide, Enviva Biomass, which is based in Bethesda, Maryland, said that its operations in Hamlet would displace fossil fuels, grow more trees and help to fight climate change.

Racism is magnifying the deadly impact of rising city heat

But opposition is building on many fronts. An expanding body of research shows that burning solid biomass to generate electricity often emits huge amounts of carbon — even more than burning coal does. In February 2021, more than 500 scientists and economists signed a letter to US president Joe Biden and other world leaders urging them to not support using wood to generate energy, arguing that it harms biodiversity and increases carbon emissions. Although pellet companies advertise that their operations consume low-quality wood, this claim has come under increased scrutiny, with mounting evidence of significant deforestation around wood-pellet plants.

Residents living near wood-pellet facilities are increasingly complaining about the harmful impacts from air pollution, traffic and noise coming from the wood-pellet operations. And in many cases, these facilities are located near marginalized communities lacking political power.

In Hamlet, 45% of the population identifies as Black, and in the tiny community closest to the mill, about 90% of people are Black, says Debra David, a local resident and activist. She calls the Enviva operation a clear case of environmental racism — layering environmental burdens on an already vulnerable population. David rattles off the names of poultry farms, a chemical company, a natural-gas plant and gravel mines in or near the town. “We are very much overloaded here,” she says.

Enviva did not respond to multiple requests to comment about concerns raised in this article relating to the Hamlet plant and its other operations.

The green gold rush

The big push towards biomass began with the European Commission’s 2009 Renewable Energy Directive, the legal framework for developing renewable energy in all sectors of the EU economy . It became known as the 20-20-20 climate and energy package, and mandated three goals to reach by 2020: reduce EU greenhouse-gas emissions by 20% from 1990 levels; increase the renewable portion of EU energy consumption to 20%; and improve EU energy efficiency by 20%. The directive was initially hailed by environmentalists for taking concrete steps towards limiting global warming to 1.5 °C above pre-industrial levels — the international goal set by the 2015 Paris climate agreement.

As part of the 20-20-20 package, the EU set standards to reduce carbon emissions by using more biofuels. Since then, EU countries have handed out substantial subsidies to the wood-pellet industry, which have amounted to billions of Euros in the past few years. An assessment from Trinomics, a consultancy firm based in Rotterdam, the Netherlands, found that ten EU countries that were analysed in the study spent more than €6.3 billion (US$6.9 billion) in subsidies for solid biomass energy to produce electricity in 2021 (see go.nature.com/3m4mbm2 ).

The support for wood biomass relies on the idea that carbon emitted by burning biomass will be absorbed by the regrowth of vegetation that replaces the trees used by the industry. But in the past decade, a growing number of scientists have challenged this assumption.

Aerial view of a biomass wood pellet production plant shows huge piles of felled logs and sawdust

Enviva’s wood-pellet manufacturing facility in Garysburg, North Carolina. Credit: Erin Schaff/The New York Times/Redux/eyevine

John Sterman, the director of the System Dynamics Group at the Massachusetts Institute of Technology Sloan School of Management in Cambridge, is one of the researchers who signed the 2021 letter. In 2018, Sterman and his colleagues did a life-cycle analysis of the effects of replacing coal with wood to generate electricity ( J. D. Sterman et al . Environ . Res . Lett . 13 , 015007; 2018 ). They found that this substitution could exacerbate climate change until at least 2100, mainly because it takes decades for trees to regrow on harvested land and to remove enough carbon dioxide from the atmosphere.

Sterman and his colleagues calculated that it would take between 44 and 104 years for new trees to absorb as much CO 2 as the amount generated by wood bioenergy that displaces coal. Despite claims that it helps the fight against global warming, he says, “our conclusion is no, it actually makes climate change worse”.

In 2019, the European Academies’ Science Advisory Council (EASAC) reviewed the EU’s policies and concluded that they are failing to recognize that removing forest carbon stocks for bioenergy leads to an initial increase in emissions (see go.nature.com/3wkqupk ). “Using biomass emits even more CO 2 to the atmosphere per energy generated than even fossil fuels,” says Michael Norton, a co-director of the environment programme at the EASAC secretariat in Vienna.

Is it too late to keep global warming below 1.5 °C? The challenge in 7 charts

Eventually, biomass energy will produce less carbon than fossil fuels do. But the time it takes to make up for the extra initial emissions, says Norton, “is so long as to worsen climate change for decades to centuries — hardly an effective climate strategy given that we are already overshooting Paris agreement targets”.

Researchers have pointed out other problems with the way wood pellets are accounted for in carbon-emission assessments. In particular, the EU accounts for greenhouse-gas emissions associated with biomass at the point of production, not the point of combustion. That allows EU countries relying on biomass to avoid including emissions from this source in their tallies and creates an incentive to use biomass energy, say Sterman and other researchers.

In 2023, the EU announced that it was considering changing its climate policies concerning energy produced from wood biofuels. Forest advocates and biomass opponents were thrilled — but the EU eventually decided that biomass from wood will remain classified as renewable energy.

When trees fall in the forest

Beyond climate concerns, some researchers also warn that the wood-pellet industry harms forests and promotes deforestation. On its website, Enviva says that it produces pellets from low-value wood, such as trees that are unsuitable for other industries, tops and limbs that cannot be processed into lumber, deformed trees and by-products from other industries, such as sawdust. The company says it “does not source from old growth forests, protected forests, or forests that are harvested for land use conservation”.

But many environmental groups and media outlets have photographed stacks of mature hardwood trees waiting to be delivered to Enviva processing plants — and the clear-cut woods left behind. The Dogwood Alliance, a non-profit conservation organization in Asheville, North Carolina, estimates that Enviva facilities in North Carolina consume about 50,000 acres of forest each year, raising questions about Enviva’s practices.

Christopher Williams, an environmental scientist at Clark University in Worcester, Massachusetts, analysed satellite data of forest cover near several Enviva pellet mills. In a report conducted for the Southern Environmental Law Center, a non-profit organization based in Charlottesville, Virginia, Williams found that rates of forest loss from 2001 to 2016 near three Enviva mills were more than double that of a region with similar forests that was not located near a mill (see go.nature.com/4fsb79w ).

“We found that the area of forest-lands cleared each year increased markedly after the initiation of pellet-mill operations,” said Williams.

Along with increasing scrutiny and criticism of the biomass industry in the past few years, some companies have run into economic headwinds. Citing debts exceeding US$2.6 billion, Enviva filed for bankruptcy in March.

A resident of Gloster, Mississippi, wearing a face maskstandins next to a vehicle with a biomass production plant in the background

In 2020, the Drax pellet plant in Gloster, Mississippi, paid a US$2.5-million penalty for air-pollution violations. Credit: Eric J. Shelton/Mississippi Today

According to the industry publication Biomass Magazine , there are now more than 100 wood-pellet plants in the United States, scattered across the country. But the world’s largest wood-pellet producers, such as Drax, based in Selby, UK, and Enviva, have staked their futures in the southeast and south of the United States.

Enviva now operates ten US wood-pellet facilities — one each in Florida, Georgia, South Carolina, and Virginia; two in Mississippi and four in North Carolina. Besides the issues of the industry’s environmental impact, there are also concerns about the effects of these operations on the health of people living nearby.

Many residents in the four counties of North Carolina where Enviva plants are located, say the wood-pellet operations have placed a heavy burden on the health of vulnerable communities.

Wood-pellet facilities in the south are about 50% more likely to be located in “communities already besieged by polluting industries and environmental injustices”, says Heather Hillaker, an attorney at the Southern Environmental Law Center in Chapel Hill, North Carolina. “So, you have all the cumulative impacts as well as the disproportionate impacts on these communities.”

Despite concerns raised about the wood-pellet industry, the North Carolina Department of Environmental Quality (DEQ) permitted the construction of Enviva’s Hamlet facility, and its subsequent requests for expansion.

Breathing problems

David describes the near-constant smell of rotten eggs that comes from living downwind of the plant, but she mostly worries about the long-term health consequences of the poor air quality. She says she started having breathing problems not long after the facility began its round-the-clock operations. At one point, her oxygen levels dipped so low that she needed supplemental oxygen daily. Now, she uses an albuterol rescue inhaler and a once-daily inhaled asthma treatment. And she says she’s not alone.

“There are 12 families in my area and 8 of them have albuterol pumps and take asthma medicine,” says David. “One lady had her child checked at four months old and she tested [positive] for asthma. That wouldn’t be happening in a newborn if this air wasn’t infected with dust.”

“The Hamlet facility is a prime example that, historically, these wood-pellet manufacturing facilities were permitted based on incorrect information about their emissions of volatile organic compounds,” says Hillaker.

“It took many, many years of submitting comments, public comments, pursuing, in some cases, lawsuits or administrative challenges to get the agencies and the companies to acknowledge the reality of the VOC [volatile organic compounds] emissions and address it through appropriate control technologies,” says Hillaker.

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Environmental organizations and communities with local wood-pellet operations have brought complaints against operators with varying levels of success. A suit filed against Enviva in North Carolina in 2019 led the state’s DEQ to require the company to invest in more-sophisticated pollution-capture devices on its smokestacks — although those living near the plants say they have not noticed a big difference in air quality.

A federal suit in Texas against another biomass company, Woodville Pellets, alleging violations of the federal Clean Air Act, led to an agreement in which Woodville paid a penalty of more than $500,000 and installed new pollution controls. As part of the agreement, Woodville Pellets denied the allegations and maintained that the agreement does not constitute an admission of liability.

After Drax’s pellet plant in Gloster, Mississippi, paid a $2.5-million civil penalty for air-pollution violations in 2020, the company settled similar claims in Bastrop, Louisiana, and Urania, Louisiana, for a total of $3.2 million in September 2022, although the company denied that it committed any violations.

Drax told Nature that it has “engaged an independent, third-party to conduct an air toxics impact analysis. Those results support that there are no adverse effects to human health from the facility and determined that no modelled pollutant from the facility exceeded the acceptable ambient concentration”. It adds that the company seeks “100% compliance with our permits and has installed additional technology to manage emissions”.

In response to concerns about carbon emissions from biomass energy, Drax says that multiple governments, as well as scientists, classify biomass as carbon neutral.

A path forward

In the heart of south Georgia lies the rural town of Adel, with a population of 5,500. The residents of the city’s west side, most of whom are Black, have lived alongside polluting industries for decades. But three years ago, the community found itself embroiled in two climate-justice battles.

The first one started in 2021, when Georgia’s Environmental Protection Division issued a permit to the Renewable Biomass Group, a wood-pellet production company, for a facility that would produce 450,000 tonnes of wood pellets per year. The company had not even broken ground for its facility when, in October 2021, another biomass company, Spectrum Energy, applied to construct and operate a wood-pellet manufacturing facility that would produce 600,000 tonnes each year, which would make it one of the largest in the world.

Concerned Citizens of Cook County (4C), a social and environmental justice organization in Adel, and 14 other public-interest organizations opposed the permit for the Spectrum plant. “We were already overburdened with multiple industries and legacy pollution,” says Treva Gear, a community activist and the founder of 4C.

Opponents of the plants said that the proposed Spectrum wood-pellet facility would further harm the neighbourhood of Black and Hispanic residents and threaten the health and welfare of local people.

In 2022, the state approved the permit for Spectrum to commence two phases of construction and operation. In December 2022, Spectrum reached out to Adel community organizers and their lawyers, at the Southern Environmental Law Center, to seek a compromise.

Although initially reluctant to bargain, Gear says that they realized that negotiation might be their best hope, because they doubted the state regulatory agency would take their side in the dispute. The two sides reached an agreement in which Spectrum pledged to mitigate potential noise and visual concerns. The agreement also includes the potential for adding more air-pollution control measures.

In an e-mail response to a request for comment about the plant’s impacts, Spectrum president Michael Ainsworth said that Spectrum’s participation in the settlement was voluntary, despite having already received a favourable ruling from the Georgia’s Environmental Protection Division. “Spectrum also agreed to be transparent with the community and to share more information than required by the regulations and also to share information more often than required,” wrote Ainsworth.

Community activists such as Gear are taking solace in winning these concessions because they can see that the deck is stacked against them with the increasing global demand for wood pellets.

“We reached a settlement agreement that put us in a position to have probably the cleanest wood-pellet plant in the world,” she says.

It’s a victory for the local community, but as the biomass industry continues to expand globally, these kinds of battle will become more common as debates over the impacts of wood pellets heat up.

Nature 632 , 726-728 (2024)

doi: https://doi.org/10.1038/d41586-024-02676-z

Melba Newsome has a fellowship from the Alicia Patterson foundation, which provided support for this story.

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Fda approves two updated covid vaccines.

Rob Stein, photographed for NPR, 22 January 2020, in Washington DC.

New COVID Vaccines

A pharmacist administers a COVID-19 vaccine.

A new round of COVID-19 vaccines will be rolled out soon. Scott Olson/Getty Images hide caption

The Food and Drug Administration Thursday gave the green light to two updated COVID-19 vaccines to help people protect themselves from the latest strains of the virus.

The new COVID vaccines are designed to keep the shots up to date with the virus, which keeps evolving to evade our immune systems.

Olympic sprinter Noah Lyles wears a black KN95 mask and a blue t-shirt with an American flag on it.

Is COVID endemic yet? Yep, says the CDC. Here's what that means

"Vaccination continues to be the cornerstone of COVID-19 prevention," said Dr. Peter Marks , director of the FDA's Center for Biologics Evaluation and Research in a statement announcing the decision. "These updated vaccines meet the agency's rigorous, scientific standards for safety, effectiveness, and manufacturing quality. Given waning immunity of the population from previous exposure to the virus and from prior vaccination, we strongly encourage those who are eligible to consider receiving an updated COVID-19 vaccine to provide better protection against currently circulating variants."

The Pfizer-BioNTech and Moderna mRNA vaccines that got the go-ahead on Thursday target the KP.2 variant . The Novavax vaccine, which is based on an older technology, targets an earlier strain called JN.1 and is expected to get the FDA's stamp of approval soon too.

An imperfect vaccine can still provide protection

Both target strains have already been overtaken by even newer variants, but they’re all still part of the omicron group. The hope is the vaccines are close enough to boost immunity and protect people through the rest of the surprisingly big summer wave and the surge expected this winter.

“The vaccine is not intended to be perfect. It’s not going to absolutely prevent COVID-19," Marks told NPR in an interview. "But if we can prevent people from getting serious cases that end them up in emergency rooms, hospitals or worse — dead — that’s what we’re trying to do with these vaccines.”

The new vaccines should cut the risk of getting COVID by 60% to 70% and reduce the risk of getting seriously ill by 80% to 90%, Marks says. The shots are expected to become available as soon as this weekend to anyone age 6 months and older.

Vaccination timing could be a personal decision

“Right now we’re in a wave, so you’d like to get protection against what’s going on right now,” Marks says. “So I would probably get vaccinated in as timely a manner as possible. Because right now the match is reasonably close. You’re probably going to get the most benefit you’re going to get from this vaccine against what’s currently circulating. So when this gets into pharmacies I will probably be on line as soon as it gets rolled out.”

To maximize the chances of getting the best protection, people should wait at least two or three months since their last bout of COVID or their last shot to get one of the new vaccines, Marks says.

Some people could consider waiting until September or October if they’re especially concerned about maximizing protection through the winter surge and over the holidays.

“Getting vaccinated sometime in the September to early October time frame seems like a pretty reasonable thing to do to help bring you protection through the December/January time frame,” says Marks. “It doesn’t, like, suddenly stop. This is not like something that suddenly cuts off at three or four months. It’s just that the immunity will decrease with time.”

Vaccination can help slow COVID's spread

“In my opinion, everyone should get one of the new vaccines,” says Dr. George Diaz , chief of medicine at Providence Regional Medical Center Everett in Everett, Wash., and a spokesperson for the Infectious Disease Society of America. “Being vaccinated yourself will prevent transmission to other people. So that will help reduce the spread of the disease in the community, especially to the most vulnerable people. So you’re not just helping yourself but also helping others.”

In addition, getting vaccinated reduces the risk for long COVID, Diaz adds.

Others question whether everyone necessarily needs another shot, arguing most younger healthy people still probably have enough immunity from all the shots and infections they’ve already gotten to protect them from getting really sick.

“Anyone who wants to get this vaccine should get it,” says Dr. Paul Offit , a vaccine expert at the University of Pennsylvania who advises the FDA. “It certainly makes sense why someone would want to get it because it lessens your chance of getting a mild or moderate infection for about four to six months and to some extent lessens your chances of spreading the virus.” But the calculation could be different for younger people. “Were I a 35-year-old healthy adult who’d already had several doses of vaccine and one or two natural infections I wouldn’t feel compelled to get it,” Offit says.

And regardless of the public health advice, it’s far from clear how many people will want one of the new shots. Only about 22% of eligible adults got one of the last ones.

But for anyone who does want the COVID vaccine, they can get the flu shot at the same time . In addition, federal officials are recommending anyone age 75 and older also get one of the new vaccines to protect against the respiratory syncytial virus , or RSV. Same goes for pregnant people and those ages 60 to 74 who are at high risk of getting seriously ill from RSV.

Older at-risk people will probably be able to get a second shot with the new COVID vaccines in the spring or early summer to help protect them against another wave next summer.

Insured people can get all three vaccines for free if they get their shot from an in-network provider. But a federal program that paid for the vaccines for uninsured adults expired.

“In the public health community we’re very concerned about how they will access protection and looking for ways for how we’re going to solve that problem,” says Dr. Kelly Moore , who runs Immunize.org , an advocacy group. “We know that the people who are uninsured are the least likely to be able to afford becoming ill – missing work, staying home from school.”

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Tea and Health: Studies in Humans

Tea, next to water is the cheapest beverage humans consume. Drinking the beverage tea has been considered a health-promoting habit since ancient times. The modern medicinal research is providing a scientific basis for this belief. The evidence supporting the health benefits of tea drinking grows stronger with each new study that is published in the scientific literature. Tea plant Camellia sinensis has been cultivated for thousands of years and its leaves have been used for medicinal purposes. Tea is used as a popular beverage worldwide and its ingredients are now finding medicinal benefits. Encouraging data showing cancer-preventive effects of green tea from cell-culture, animal and human studies have emerged. Evidence is accumulating that black tea may have similar beneficial effects. Tea consumption has also been shown to be useful for prevention of many debilitating human diseases that include maintenance of cardiovascular and metabolic health. Various studies suggest that polyphenolic compounds present in green and black tea are associated with beneficial effects in prevention of cardiovascular diseases, particularly of atherosclerosis and coronary heart disease. In addition, anti-aging, antidiabetic and many other health beneficial effects associated with tea consumption are described. Evidence is accumulating that catechins and theaflavins, which are the main polyphenolic compounds of green and black tea, respectively, are responsible for most of the physiological effects of tea. This article describes the evidences from clinical and epidemiological studies in the prevention of chronic diseases like cancer and cardiovascular diseases and general health promotion associated with tea consumption.

INTRODUCTION

Tea, the most popular beverage consumed by two-thirds of the world’s population is made from the processed leaf of Camellia sinensis . Tea types, based on processing or harvested leaf development are black (fermented), green (non-fermented) and oolong (semi-fermented). These major tea types differ in how tea is produced and processed according to the different processes of drying and fermentation that determine its chemical composition. Green tea is produced by using young tea leaves and sold for consumption without fermentation after withering, steaming or pan firing, drying and grading. Pan firing is required to prevent the tea leaves from fermenting by the natural enzyme activities. Tea leaves are allowed to ferment for several hours before being either smoke fired, flame fired or steamed to make black tea. Oolong tea is produced by a partial oxidation of the leaf, intermediate between the process for green and black tea [ 1 ]. Black tea is made by first exposing the tea leaves to air, causing them to oxidize. This oxidation process turns leaves into a deep brown color and during this process, the flavor is intensified. The leaves are then left as such or are heated, dried and crushed. Green tea is best studied for its health benefits, including cancer chemopreventive and chemotherapeutic effects [ 2 , 3 ], but emerging data is showing that black tea may possess similar health promoting attributes.

Green tea contains characteristic polyphenolic compounds, (−)-epigallocatechin-3-gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG) and (−)-epicatechin (EC). Flavonols, including quercetin, kaempferol, myricitin and their glycosides are also present in tea.

A typical cup of green tea usually contains 250–350 mg tea solids, of which 30–42% are catechins and 3–6% caffeine [ 4 ]. The major active constituents of tea are catechins, and among them, EGCG is the most potent and much of the anticarcinogenic effect of green tea is predominantly credited to it. Some catechins are oxidized or condensed to theaflavins (theaflavin, theaflavin-3-gallate, theaflavin-3′-gallate and theaflavin-3-3′-digallate) (3–6%) and thearubigins (12–18%) during fermentation of fresh tea leaves and are responsible for the bitter taste and dark color of black tea. Black tea contains mainly thearubigins, theaflavins, flavonols and catechins. The total polyphenol content of green and black teas is similar, but with different types of flavonoids present due to the degree of oxidation during processing [ 5 ].

I. METABOLISM AND BIOAVAILABILITY

For all catechins, the metabolic pathways of methylation, glucuronidation and sulfation have been observed. Methylation, a major metabolic pathway, forms the metabolites 3′ and 4′- O -methyl-(−)-EC and O -methyl-(−)-EC-glucuronide, 4″- O -methyl-ECG, 4′- O -methyl-EGC, 4″- O -methyl-EGCG and 4′,4″-di- O -methyl-EGCG, and 4″- O -methyl-EGCG-3′- O -glucuronide and 3′,4′- or 3′,5′-di- O -methyl-EGCG-4″- O -glucuronide [ 6 ]. In human liver cytosol, (−)-EC was efficiently sulfated mainly through SULT1A1 while in the intestine, both SULT1A1 and SULT1A3 also contributed to the sulfation. (−)-EC was not glucuronidated by human liver and small intestinal microsomes. It has also been reported that there was no confirmation of glucuronidation by human colon microsomes or by recombinant UDP-glucuronosyltransferase-1A7 (UGT1A7), which is present in stomach and esophagus, but not in liver. (−)-EC was efficiently glucuronidated with the formation of two glucuronides in rat liver microsomes. Sulfation of (−)-EC was a major pathway in human liver and intestine without glucuronidation [ 7 ]. The absorption of green tea catechins in the small intestine is quite small. Flavanols are absorbed without deconjugation or hydrolysis and pass through biological membranes. The greater part of ingested green tea catechins reaches the large intestine and encounters the colonic microflora, with further hydrolysis of glycosides into aglycones and extensive transformation into various aromatic acids like phenylvalerolactones and hydroxyphenylpropionic acids [ 8 ]. In humans, plasma bioavailability of green tea catechins is very low. After the administration of either 697 mg of green tea or 547 mg of black tea to healthy volunteers, plasma EGC and EC content was 0.26–0.75% compared with EGCG and ECG with 0.07–0.20% with similar observations in urine [ 9 ]. With a single catechin, plasma concentration was found to be 1.53 M at a dose of 1050 mg for (−)-EC, 3.1 μM at a dose of 664 mg for ECG, 5 μM at a dose of 459 mg for EGC and 6.35 μM at a dose of 1600 mg for EGCG [ 6 ]. Six metabolites were identified in human urine: (−)-EC-glucuronide, three (−)-EC-sulfates, two O -methyl-(−)-EC-sulfates. Microbial metabolites (−)-5-(3′,4′-dihydroxyphenyl)-γ-valerolactone, and their glucuronide conjugates were also present. The major pathway for the elimination of EGCG is the biliary excretion. The total amount of metabolites excreted in urine is associated with maximum plasma concentrations. Urinary recovery was 0.5–6% for some tea catechins [ 10 ]. The half-lives of flavanols are 2–3 h in plasma, except EGCG, which is eliminated more slowly probably due to higher biliary excretion and greater complexing with plasma proteins [ 11 ].

II. CANCER PREVENTIVE EFFECTS OF TEA IN HUMANS

Earliest documented cancer preventive effect of tea is our study in 1988 [ 12 ]. Currently, there are 1000 scientific publications in the scientific literature found on PubMed documenting cancer preventive ability of tea. Several studies initiated in our laboratory and subsequently verified from many other laboratories have suggested that catechins and theaflavins found in tea may reduce the risk of various types of cancers in humans. Various reports have shown an inverse association of tea consumption with the development of certain types of cancer [ 2 , 13 , 14 ]. The reported effects of tea on skin, prostate, lung and breast cancer in humans are shown in Table 1 .

Reported Effects of Tea on Skin, Prostate, Lung and Breast Cancer in Humans.

Effects of tea in humans	References


Significant marked decrease risk of skin squamous cell carcinoma by intake of black tea	[ ]
Protective effect of tea on cutaneous malignant melanoma risk	[ ]
Treatment with Polyphenon E ointment showed complete clearance of all baseline and new anogenital warts in immunocompetent patients	[ ]

In patients with androgen independent prostate carcinoma, green tea supplementation	[ ]
caused Grade 1 or 2 toxicity in 69% of patients along with Grade 3 toxicity and one episode of Grade 4 toxicity	[ ]
The risk of PCa declined with increasing frequency, duration and quantity of green tea supplementation in a case-control study in China	[ ]
In patients with hormone refractory prostate cancer, green tea had minimal clinical activity	[ ]
In high-grade prostate intraepithelial neoplasia volunteers, green tea catechins-treated men showed PSA values constantly lower with respect to placebo-treated ones with reduced lower urinary tract symptoms	[ ]
Dose-dependent decrease in the risk of advanced PCa by intake of green tea in Japan	[ ]
Significant reduction in serum levels of PSA, hepatocyte growth factor and vascular endothelial growth factor in men with prostate cancer after treatment with Polyphenon E	[ ] [ ]
Treatment with Polyphenon E caused changes in the levels of serum PSA, serum insulin-like growth factor axis and oxidative DNA damage in blood leukocytes	[ ]

Reduced risk of lung cancer in male cigarette smokers by tea drinking in Uruguay	[ ]
Reduced risk of lung cancer among non-smoking women by consumption of green tea	[ ]
Decrease in urinary 8-hydroxydeoxyguanosine after drinking decaffeinated green tea among smokers in a phase II trial	[ ]
Protective effect of black tea in non-smoking women	[ ]
In a case-control study in Taiwan, higher risk of lung cancer in smokers who never drank green tea, as compared to smokers who drank more than 1 cup/day of green tea	[ ]

Consumption of more than 5 cups of green tea/day by stages I and II breast cancer patients showed a lower recurrence rate and a longer disease-free period compared to those consuming less than 4 cups/day	[ ]
Reduced risk for breast cancer with green tea consumption and a possible late-stage, promotional effect of black tea on breast cancer	[ ]
Decreased risk of developed breast cancer in a case-control study with breast cancer confirmed patients by ingestion of green tea	[ ]
Increased green tea consumption of more than 3 cups/day was inversely associated with breast cancer recurrence	[ ]
No association between green tea drinking and breast cancer risk

This review article describes the major epidemiological and clinical studies on tea consumption and the risk of cancer at different organ sites in humans. We also present the evidences for the association of tea drinking and its effects on diabetes, arthritis and neurological system in humans.

i. Tea and Skin Cancer

Various studies have reported beneficial effects of regular tea consumption against squamous cell carcinoma of the skin. In a population-based case-control study, adjusting for brewing time, the association between squamous cell carcinoma and hot black tea consumption suggests a significantly lower risk in consumers of hot tea compared to non-consumers. It was suggested that tea concentration, brewing time and beverage temperature have major influences on the potential protective effects of hot black tea in relation to squamous cell carcinoma of the skin [ 15 ]. A population-based case-control study was conducted to evaluate the relationships between citrus peel use and black tea intake and squamous cell carcinoma of the skin. The independent and interactive effects of citrus peel and black tea in the development of squamous cell carcinoma were also assessed. Subjects who reported consumption of both hot black tea and citrus peel had a significant marked decrease risk of skin squamous cell carcinoma suggesting that both citrus peel use and strong black tea had protective effects in relation to squamous cell carcinoma of the skin [ 16 ]. In a case-control study conducted in Italy, a significant inverse association between vitamin A intake and cutaneous malignant melanoma risk was found. There was no appreciable association of cutaneous malignant melanoma risk with selected food items, including fish, meat, vegetables, fruit, dairy products, whole meal bread, alcohol, coffee and tea drinking. Consumption of tea had a protective effect on cutaneous malignant melanoma risk [ 17 ]. The effect of Polyphenon E ointment was investigated for efficacy and safety in the treatment of anogenital warts in immunocompetent men and women. Polyphenon E 15% or 10% ointment or matching vehicle was self-applied by 530 patients three times daily to all warts. The assessment of response and of adverse events was performed biweekly until complete clearance or for up to 16 weeks. Treatment with 10 and 15% Polyphenon E ointment showed complete clearance of all baseline and new anogenital warts in 51 and 53% of patients, respectively. It was also noted that 78% of all patients treated with either 10 or 15% Polyphenon E ointment showed wart clearance rates of 50% or better. There were only mild or moderate adverse effects as demonstrated by the safety profile of Polyphenon E ointments [ 18 ].

ii. Tea and Prostate Cancer

Among many dietary agents investigated for chemopreventive properties against prostate cancer (PCa), green tea and its constituent polyphenols (GTP) have received much attention. A Phase II trial was conducted in patients with androgen independent prostate carcinoma to investigate the explored the antineoplastic effects of green tea. Forty two patients asymptomatic who had manifested, progressive prostate specific antigen (PSA) elevation with hormone therapy were evaluated. Six grams of green tea per day orally in 6 divided doses were given to patients and each dose contained 100 calories and 46 mg of caffeine. A decline in more than or equal to 50% in the baseline PSA value occurred in a single patient and it was not continued beyond 2 months. Median change in the PSA value increased by 43% at the end of the first month. Grade 1 or 2 green tea toxicity occurred in 69% of patients, along with Grade 3 toxicity and one episode of Grade 4 toxicity [ 19 ]. In Hangzhou, southeast China, a case-control study was conducted in 130 incident patients with histologically confirmed adenocarcinoma of the prostate. The risk of PCa declined with increasing frequency, duration and quantity of green tea consumption and there were significant dose-response relationships, suggesting preventive effects of green tea [ 20 ]. The efficacy of green tea capsules was tested on patients with hormone refractory prostate cancer (HRPCa) by Choan et al. [ 21 ]. Efficacy of green tea, prescribed as an alternative complementary formulation was tested on HRPCa. PSA was the primary endpoint and estimates after a minimum of 2 months of therapy. It was found that 12 patients reported at least one side effect among 19 patients enrolled into the study. The minimum 2 months of therapy was not completed by 4 patients and 15 patients completed at least 2 months of therapy. Within 2 months of starting therapy, progressive disease was noted in 9 of these patients and 6 patients developed it after additional 1 to 4 months of therapy. Therefore, based on the results of this study, it was concluded that green tea had minimal clinical activity against HRPCa [ 21 ]. In high-grade prostate intraepithelial neoplasia volunteers, a clinical trial was conducted to assess the safety and efficacy of green tea catechins for the chemoprevention of PCa. Daily treatment consisted of three green tea catechins capsules 200 mg each. Only one tumor was diagnosed among the 30 green tea catechins-treated men with an incidence of 3%, whereas nine cancers were found among the 30 placebo-treated men with an incidence of 30% after 1 year. There was no significant change in total PSA between the two arms, but green tea catechins-treated men showed values constantly lower with respect to placebo-treated ones. International Prostate Symptom Score and quality of life scores of green tea catechins-treated men with coexistent benign prostate hyperplasia, a condition prevalent in older men were also improved. There were no reports of significant side effects and administration of green tea catechins also reduced lower urinary tract symptoms [ 22 ]. Green tea consumption habit of 49,920 men aged 40–69 years was investigated in the Japan Public Health Center-based prospective study. During that time, 404 men were newly diagnosed with PCa, of which 114 had advanced cases, 271 were localized, and 19 were of an undetermined stage. It was established that localized PCa was not affected by the consumption of green tea, there was a dose-dependent decrease in the risk of advanced PCa by intake of green tea [ 23 ]. It has been reported that there was a significant reduction in serum levels of PSA, hepatocyte growth factor and vascular endothelial growth factor in men with prostate cancer after brief treatment with green tea extract containing EGCG (Polyphenon E), with no elevation of liver enzymes [ 24 ]. In PCa patients scheduled to undergo radical prostatectomy, a randomized, double-blind, placebo-controlled trial of Polyphenon E was conducted to determine the bioavailability of GTP in prostate tissue and to measure its effects on systemic and tissue biomarkers of PCa. Polyphenon E or placebo daily was given to patients for 3 to 6 weeks before surgery. Treatment with Polyphenon E caused promising but not statistically significant changes in the levels of serum PSA, serum insulin-like growth factor (IGF) axis, and oxidative DNA damage in blood leukocytes. In the prostatectomy tissue, tissue biomarkers of cell proliferation, apoptosis, and angiogenesis did not differ between the treatments. Patients receiving Polyphenon E had a decrease in Gleason score between biopsy and surgical specimens but it was not statistically significant [ 25 ].

iii. Tea and Lung Cancer

Various studies have demonstrated the relationship between tea consumption and threat of lung cancer. Tea drinking was associated with reduced risk of lung cancer in male cigarette smokers in a case control study in Uruguay [ 26 ]. In a population-based case-control study in Shanghai, China, consumption of green tea was associated with a reduced risk of lung cancer among non-smoking women and the risk decreased with increasing consumption [ 27 ]. There was a significant decrease in urinary 8-hydroxydeoxyguanosine after drinking decaffeinated green tea among smokers over a 4 month-period in a randomized controlled tea intervention phase II trial [ 28 ]. In a case control study, a protective effect of frequent, daily or several times/week black tea drinking appeared among non-smoking women [ 29 ]. The maximum tolerated dose of green tea extract (GTE) in patients with advanced lung cancer was determined by Laurie et al. Seventeen patients with advanced lung cancer were given oral doses of GTE once daily, starting with a dose of 0.5 g/m 2 /day with increasing doses. The maximum tolerated dose of GTE was found to be 3 g/m 2 /day without grade 3 or 4 toxicity [ 30 ]. A case-control study was conducted on 241 lung cancer patients in Taiwan and the effects of smoking, green tea consumption, IGF1, IGF2, and IGFBP3 polymorphisms were evaluated on lung cancer risk. It was found that lung cancer cases had a higher proportion of smoking, green tea consumption of <1 cup/day, exposure to cooking fumes and family history of lung cancer than controls. There was higher risk of lung cancer in smokers who never drank green tea, as compared to smokers who drank green tea >1 cup/day [ 31 ].

iv. Tea and Breast Cancer

Epidemiological studies have demonstrated inconsistent results of the relation between green tea intake and risk of breast cancer. Stages I and II breast cancer patients showed a lower recurrence rate and a longer disease-free period when consuming more than 5 cups of green tea/day compared to those consuming less than 4 cups/day [ 32 ]. A significant inverse relationship between intake of green tea and risk of breast cancer was reported in a case-control study conducted among Asian-American women in Los Angeles County. In a meta-analysis published by Sun et al., 13 studies were examined and data on consumption of either green tea or black tea, or both in relation to breast cancer risk was provided [ 33 ]. The combined results from the four studies indicated a reduced risk of breast cancer for highest versus non/lowest intake for green tea. Contradictory results were observed in case-control as compared to cohort studies for black tea. There was a minor inverse association between black tea consumption and risk of breast cancer by the combined results from the eight case-control studies. Modest increase in risk was found to be associated with black tea intake in five cohort studies. Therefore, the meta-analysis concluded that there was a lower risk for breast cancer with green tea consumption and a possible late-stage, promotional effect of black tea on breast cancer [ 33 ]. The consumption of green tea was associated with a reduced risk of developed breast cancer in a case-control study with breast cancer confirmed patients [ 34 ]. Ogunleye et al., performed a meta-analysis of studies of breast cancer risk and recurrence including 5,617 cases of breast cancer. They identified two studies of breast cancer recurrence and seven studies of breast cancer incidence. The results of the analysis indicated that the increased green tea consumption of >3 cups a day was inversely associated with breast cancer recurrence. There was an inverse association with green tea consumption following analysis of case-control studies of breast cancer incidence while no association was found among cohort studies of breast cancer incidence [ 35 ]. From the baseline survey in 1990–94, 581 cases of breast cancer were newly diagnosed in 53,793 women during 13.6 years follow-up in a Japan Public Health Center-based Prospective Study. In 1995–98, after the 5-year follow-up survey, 350 cases were newly diagnosed in 43,639 women. The frequency of total green tea drinking was assessed by the baseline questionnaire, while two types of green tea, Sencha and Bancha/Genmaich were assessed by 5-year follow-up questionnaire. The adjusted hazard ratio [HR] for women who drank >/= 5 cups/day was 1.12 in the baseline data as compared with women who drank <1 cup of green tea/week. The adjusted HR for women who drank >/=10 cups/day were 1.02 for Sencha and 0.86 for Bancha/Genmaicha as compared with women who drank <1 cup of Sencha or Bancha/Genmaicha/week. This study found no association between green tea drinking and risk of breast cancer [ 36 ]. A phase I dose escalation trial in women with a history of stage I to III hormone receptor-negative breast cancer was conducted. Polyphenon E was given at different doses twice daily or matching placebo for 6 months. The primary endpoint of the study was to establish the maximum tolerated dose (that causes 25% dose-limiting toxicity). At baseline and 6 months, a mammogram and random core biopsy of the contralateral breast were obtained along with serial blood/urine collections every 2 months for biomarker analyses. After treatment with 400 mg of Polyphenon E, there was one dose-limiting toxicity, three dose-limiting toxicities at 600 mg and one dose-limiting toxicity at 800 mg. At 600 mg of Polyphenon E, the dose-limiting toxicity rate was 27% and the maximum tolerated dose for Polyphenon E was found to be 600 mg twice daily [ 37 ].

v. Tea and other Cancers

Tea consumption has been reported to have beneficial effects against several types of cancers. Consumption of green tea was associated with a lower risk of esophageal cancer in a case-control study of esophageal cancer patients in Shanghai [ 38 ]. In a prospective cohort study in Yoshimi town in Saitama Prefecture, respondents were divided into three groups according to daily consumption of green tea: less than 3 cups, from 4 to 9 cups, and more than 10 cups. Individuals who consumed more than 10 cups of green tea/day showed remarkable reduction of relative risk for lung, colon, and liver cancers [ 39 ]. It has been reported in a study that consumption of black tea reduces colon cancer risk in both men and women [ 40 ]. The association between green tea consumption and colorectal cancer risk was evaluated in a population-based prospective cohort stud which included 60,567 Chinese men aged 40–74 years at baseline. The subjects were followed up for 5 years and 243 incident cases of colorectal cancer were identified. Regular green tea consumption of at least three times/week for more than six consecutive months was related with reduced risk of colorectal cancer in non-smokers and the risk decreased with the increased amount of green tea consumption. Each 2 g rise of intake of dry green tea leaves/day was associated with a 12% reduction in risk of colorectal cancer. However, there was no significant association of green tea consumption with the risk of colorectal cancer among smokers suggesting that regular consumption of green tea may reduce colorectal cancer risk among non-smokers [ 41 ]. A total of 13 epidemiological studies consisting of six case-control and seven prospective cohort studies were included in a meta-analysis to evaluate the association between tea consumption and the risk of primary liver cancer. An inverse association with a borderline significance was found between tea consumption and primary liver cancer with demonstrated preventive effects of tea intake on the development of primary liver cancer in both men and women. It was concluded that green tea consumption was associated with a moderate reduction in risk for primary liver cancer [ 42 ]. The association between green tea drinking and the risk of pancreatic cancer was investigated in a population-based case-control study in urban Shanghai with recruitment of 908 patients of pancreatic cancer and 1067 healthy controls. Interview questionnaire was filled by the subjects to give information on tea drinking, type of tea, amount of tea consumption, temperature of tea, and the duration of regular tea drinking. Regular green tea drinking was associated with 32% reduction of pancreatic cancer risk as compared to those who did not drink tea regularly in women with increased consumption and longer duration of tea drinking associated with reduced pancreatic cancer risk. Lower temperature of tea was associated with reduced risk of pancreatic cancer in both men and women, irrespective of the amount or duration of tea drinking among regular tea drinkers [ 43 ]. In case control studies on the relationship between gastric cancer and tea consumption conducted in China and Japan, a significant inverse relationship was found in four studies and an insignificant inverse relationship was found in two studies [ 44 ].

III. TEA AND CARDIOVASCULAR DISEASES

Consumption of tea is increasingly being shown to be associated with enhanced cardiovascular and metabolic health. Green tea caused an increase in the activity of enzymes implicated in cellular protection against reactive oxygen species: superoxide dismutase in serum and the expression of catalase in the aorta. This action is combined with direct action on oxygen species by a decrease in the nitric oxide plasma concentration [ 45 ]. Green tea catechins affect lipid metabolism by different pathways and prevent the appearance of atherosclerotic plaque. Its intake decreases the absorption of triglycerides and cholesterol and these findings are in accordance with the fact that it increases excretion of fat [ 46 ]. In patients, who underwent coronary arteriography for the first time in China, green tea consumption was associated with a reduced risk of coronary artery disease in male patients, with an adjusted odds ratio of 0.62 compared with those who did not drink green tea. Compared to non-tea drinkers, the adjusted odds ratios were 1.09 in male patients consuming less than 125 g of dried green tea leaves per month, 0.36 for 125–249 g per month and 0.36 for more than or equal to 250 g per month. There were similar dose-response relationships for frequency, duration, concentration and starting age of green tea drinking in male patients, while no inverse association was found between green tea consumption and coronary artery disease in female patients [ 47 ]. In a matched case-control analysis including 518 myocardial infarction, 333 hemorrhagic stroke, and 1927 ischemic stroke cases, the associations of these lifestyle factors with myocardial infarction and stroke were evaluated. Alcohol consumption was inversely associated with myocardial infarction, tea consumption was inversely associated with hemorrhagic and ischemic stroke and weight increase from age 20 to 40 was positively associated with myocardial infarction and stroke in a dose-response manner [ 48 ]. In a case-control study in southern China, a significant decrease in ischemic stroke risk was observed for drinking at least one cup of tea weekly when compared with infrequent or non-drinkers, the risk reduction being largest by drinking one to 2 cups of green or oolong tea daily. Significant inverse dose-response relationships were also found for years of drinking and the amount of dried tea leaves brewed [ 49 ]. In a meta-analysis, data from 9 studies involving 4378 strokes among 194,965 individuals was pooled. Individuals consuming more than or equal to 3 cups of tea/day had a 21% lower risk of stroke than those consuming less than 1 cup/day regardless of their country of origin with the proportion of heterogeneity not explained by chance alone being 23.8% [ 50 ].

IV. TEA AND DIABETES

Various studies have shown that tea may affect glucose metabolism and insulin signaling, causing interest in the health effects of tea consumption on diabetes. In a large cohort of U.S. middle-aged and older women from the Women’s Health Study, women who consumed more than or equal to 4 cups/day of tea had a 30% lower risk of developing type 2 diabetes than did those who did not consume tea [ 51 ]. In a retrospective cohort study among Japanese adults, adults who consumed more than or equal to 6 cups/day of green tea lowered their risk of diabetes by 33%, while no association with diabetes risk was found for oolong or black teas. Consumption of more than or equal to 3 cups/day of coffee lowered the risk of diabetes by 42% and high caffeine intake was also associated with a 33% reduction in risk of diabetes. A lowered diabetes risk was also observed in women after green tea and caffeine consumption [ 52 ]. The effects of continuous ingestion of a catechin-rich beverage in patients with type 2 diabetes who were not receiving insulin therapy in a double-blind controlled study were investigated. The patients were given green tea containing either 582.8 mg of catechins or 96.3 mg of catechins/day for 12 weeks. Waist circumference decreased in the catechin group than in the control group at 12 weeks. There was increase in insulin and the decrease in hemoglobin A(1c) levels in the catechin group than in the control group in patients treated with insulinotropic agent [ 53 ]. The possible effects of different daily doses of black tea intake on certain oxidative stress, inflammatory and metabolic biomarkers in patients with type 2 diabetes mellitus. Patients were given 150, 300, 450 and 600 ml of black tea extract (BTE) during the weeks 1, 2, 3 and 4, respectively, while the control group received 150 ml BTE throughout the intervention period. It was found that serum total antioxidant capacity was enhanced similarly in both test and control groups, but a suppressing effect on serum malondialdehyde was observed with daily intake of 2 cups of BTE. After ingesting 4 cups (600 ml) of BTE a day, there was decrease in the level of serum C-reactive protein and increase in the glutathione levels. It was concluded that regular consumption of BTE had anti-oxidative and anti-inflammatory effects in patients with type 2 diabetes mellitus [ 54 ].

V. TEA AND ARTHRITIS

Few studies have reported the beneficial effects of tea against arthritic disease in humans. In a study in Britain, it was found that those who drank tea had greater bone mineral density than those who did not drink tea [ 55 ]. Coffee, tea, and caffeine consumption were evaluated as risk factors for rheumatoid arthritis onset among older women in a prospective cohort study. Compared with those reporting no use, subjects drinking more than or equal to 4 cups/day of decaffeinated coffee were at increased risk of rheumatoid arthritis. In contrast, women consuming more than or equal to 3 cups/day of tea displayed a decreased risk of rheumatoid arthritis compared with women who never drank tea, while caffeinated coffee and daily caffeine intake were not associated with the development of rheumatoid arthritis. The associations of rheumatoid arthritis onset with the highest categories of decaffeinated coffee and tea consumption were stronger in women with seropositive disease compared with those with seronegative disease [ 56 ].

VI. TEA AND NEUROLOGICAL EFFECTS

Due to lack of well-controlled clinical trials, the effect of tea in the progression of neurodegenerative disorders has not been studied on a large scale. The protective effect of EGCG against neuronal diseases may involve its radical scavenging and iron chelating activity and/or regulation of antioxidant protective enzymes. Reduced risk for Parkinson’s disease was observed for more than or equal to 2 cups/day of tea consumption and two or more cola drinks/day. The associations for tea and cola drinks were not affected by smoking or coffee consumption [ 57 ]. A case control study was conducted in China to examine the relationship between coffee and tea drinking, cigarette smoking, and other environmental factors and risk of Parkinson’s disease. It was found that one unit of coffee and tea (3 cups/day for 10 years) would lead to 22% and 28% risk reduction, respectively, of Parkinson’s disease demonstrating a dose-dependent protective effect of coffee and tea in an ethnic Chinese population [ 58 ]. The association of coffee and tea consumption with the risk of incident Parkinson’s disease among 29,335 Finnish subjects aged 25 to 74 years without a history of Parkinson’s disease at baseline was investigated. There were followed up for 12.9 years and during this time, 102 men and 98 women developed an incident Parkinson’s disease. It was noted that subjects who habitually drank ≥ 3 cups of tea/day had a reduced risk of incident Parkinson’s disease [ 59 ]. In the Singapore Chinese Health Study, a prospective cohort of 63,257 Chinese men and women, all 157 incident Parkinson’s disease cases were identified. There was an inverse relationship of black tea with Parkinson’s disease risk that was not confounded by total caffeine intake or tobacco smoking, while green tea was unrelated to Parkinson’s disease risk [ 60 ].

VII. CONCLUSION

Tea is the most widely consumed beverage in the world, next only to water. There is often a misconception, essentially a marketing gimmick, that herbal tea is also tea. However, herbal tea is not made from the plant Camellia sinensis . Due to the popularity of tea, generally on a common trip to the grocery store, at least in US markets, one can find many types of tea preparations sold which are supplemented with various extracts of mango, strawberry, pomegranate, lemon, etc. These marketing strategies have boosted the sale of tea products to a non-tea drinking population. Similarly, tea constituents supplemented cosmetics and other products are sold to consumers.

It is increasingly appreciated that tea contains polyphenols and other components that may reduce the risk of developing chronic diseases such as cancer, cardiovascular diseases, arthritis and diabetes. More recently, the beneficial properties associated with daily consumption of green tea are getting better recognized. Particularly interesting are the studies which report that green tea reduces the risk of cancer, which is the major cause of mortality throughout the world. It has become increasingly clear that tea acts as a chemopreventive agent against a wide range of cancers. To evaluate the efficacy of tea against cancer, clinical trials are being conducted. Encouraging data from many trials are available and from many ongoing trials are awaited. However, results from human studies are not always positive, may be, due to the fact that the higher doses of tea are used in animal studies than those consumed by humans and in animal studies, the experimental conditions are generally optimized for the evaluation of a protective effect. Large scale well-controlled human clinical trials are necessary to establish the health promoting effects of tea consumption. Only based on these findings, recommendations to human population could be made.

Acknowledgments

The authors are thankful for support to National Institutes of Health, National Cancer Institute Grants R01CA120451 (to HM) and R03CA153961 (to NK).

CONFLICT OF INTEREST

The authors confirm that this article content has no conflicts of interest.

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Federal government grants first floating offshore wind power research lease to Maine

FILE - Turbines operate at the Block Island Wind Farm, Dec. 7, 2023, off the coast of Block Island, R.I. (AP Photo/Julia Nikhinson, File)

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PORTLAND, Maine (AP) — The federal government issued on Monday the nation’s first floating offshore wind research lease to the state of Maine, comprising about 23 square miles (60 square kilometers) in federal waters.

The state requested the lease from the federal Bureau of Ocean Energy Management for a floating offshore wind research array with up to a dozen turbines capable of generating up to 144 megawatts of renewable energy in waters nearly 30 miles (48 kilometers) southeast of Portland, Maine.

The research array will use floating offshore wind platforms designed by the University of Maine and deployed by partner Diamond Offshore Wind. But construction is not likely for several years.

The research is key to growing the ocean wind energy industry in Maine.

Democratic Gov. Janet Mills signed a bill last year that aims to see Maine procure enough energy from offshore wind turbines to power about half its electric load by 2040, and the state has selected a site to build, stage and deploy the turbine equipment. In the next decade, University of Maine researchers envision turbine platforms floating in the ocean beyond the horizon, stretching more than 700 feet (210 meters) skyward and anchored with mooring lines.

“Clean energy from offshore wind offers an historic opportunity for Maine to create good-paying jobs, reduce our reliance on fossil fuels, and fight climate change by cutting greenhouse gas emissions,” Mills said.

The state requested the lease in 2021. The roughly 23 square miles (60 square kilometers) in the federal lease is larger than the state’s request of about 15 square miles (39 square kilometers). It will allow the state, the fishing community, oceanography experts and the offshore wind industry to thoroughly evaluate the compatibility of floating offshore wind.

Floating turbines are the only way some states can capture offshore wind energy on a large scale. In the U.S. alone, 2.8 terawatts of wind energy potential blows over ocean waters too deep for traditional turbines that affix to the ocean floor, according to the National Renewable Energy Laboratory . That’s enough to power 350 million homes — more than double the number of existing homes in the U.S.

President Joe Biden has made offshore wind a key part of his plans for fighting climate change.

Since the start of his administration, the Department of the Interior has approved the nation’s first nine commercial scale offshore wind projects with a combined capacity of more than 13 gigawatts of clean energy — enough to power nearly 5 million homes.

IMAGES

(PDF) Green tea extract and reproduction: A review
Green Tea Science Brewing Technique Book: 12 Scientifically Proven
Benefits Of Green Tea Journal
(PDF) The analysis of quality and antioxidant activity of green tea
(PDF) Efect of Green Tea on Health: A Review
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COMMENTS

Beneficial effects of green tea: A literature review
Articles included in the study covered the following effects of green tea: (1) the health benefits in humans and animals, (2) absorption of metal ions and drug-metabolizing enzymes, (3) antioxidation and inhibition of oxidative stress, (4) carbohydrate metabolism and diabetes mellitus, and (5) adverse effects.
A Review of the Role of Green Tea ( Camellia sinensis ) in
Green tea polyphenols have also been observed to exhibit potential effects in inhibiting tooth decay and reducing blood pressure, along with antibacterial, antioxidant, ... Future research should focus on humans, to identify if the same effects can be reproduced. Clinical trials should be undertaken to identify the optimum dose of green tea in ...
Green Tea (Camellia sinensis): A Review of Its Phytochemistry
Green tea, as a non-fermented tea, retains the original chemical components of tea completely. This section details the research on green tea in phytochemistry and classifies the main compounds in green tea. The chemical structures of the main compounds that have been identified are listed in the figures below. 3.1.
Green tea: Current trends and prospects in nutraceutical and
Tea, which originated in China, has spread to every part of the world and become the most popular beverage, second to water. This review aims to broaden existing knowledge offering insights into the nutritional value of green tea, and its pharmacological effects on humans. Additionally, its nutraceutical and pharmaceutical formulations, patents ...
Green tea and cancer and cardiometabolic diseases: a review of the
A recent review of green tea and esophageal suggests an inverse association of RR = 0.65 (95% CI: 0.57-0.73) [] contrary to previous reviews reporting null associations [46, 47].Some individual ...
A comprehensive review on the effects of green tea and its components
A variety of chemical components are found in green tea, including polyphenols, purine alkaloids, amino acids and polysaccharides, etc. In green tea, various compounds act on different immune cells or even the same type of cell, causing diverse effects on the immune system (Fig. 6). According to the current research results, we speculate that ...
Effects of green tea and roasted green tea on human responses
However, the amounts of catechins (green tea: 94.4 mg/roasted green tea: 37.4 mg) and theanine (green tea: 6 mg/roasted green tea: not detected) ingested by participants in this study were ...
An Update on the Health Benefits of Green Tea
Green tea, which is produced from the leaves of the Camellia sinensis plant, is one of the most popular beverages worldwide. Over the past 30 years or more, scientists have studied this plant in respect to potential health benefits. Research has shown that the main components of green tea that are associated with health benefits are the catechins. The four main catechins found in green tea are ...
Recent Advances in the Understanding of the Health Benefits and
Tea, leaf, or bud from the plant Camellia sinensis, make up some of the beverages popularly consumed in different parts of the world as green tea, oolong tea, or black tea. More particularly, as a nonfermented tea, green tea has gained more renown because of the significant health benefits assigned to its rich content in polyphenols. As a main constituent, green tea polyphenols were documented ...
First evidence on the causal association between green tea and
The primary findings underscore a significant association between green tea intake and gastrointestinal diseases (p = 0.001), indicating heightened consumption of green tea could lead to a reduced risk of gastrointestinal diseases ... Compared with traditional epidemiological research methods, MR has the ability to reveal causal relationships ...
Green tea effects on cognition, mood and human brain function: A
Catechin. epigallocatechin gallate. The reviewed studies presented evidence that green tea influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI). The effects of green tea cannot be attributed to ….
Effects of green tea consumption on glycemic control: a systematic
The results of human clinical trials investigating the effects of green tea on glycemic control are inconsistent. We conducted a systematic review and meta-analysis of RCTs that examined the effects of green tea supplementation on glycemic control. A literature search in PubMed, Embase, and Cochrane Library databases for RCTs that investigated the effect of green tea consumption on glycemic ...
(PDF) GREEN TEA (CAMELLIA SINENSIS) AND ITS ANTIOXIDANT ...
Abstract. Tea (Camellia sinensis) is one of the most widely consumed beverages in the world. Tea extracts are source of polyphenols, which are antioxidant components. Green tea phenolic compounds ...
Effect of green tea on glucose control and insulin sensitivity: a meta
The results of studies investigating the effect of green tea on glucose control and insulin sensitivity in humans are inconsistent. ... Research Article | Volume 98, ISSUE 2, P340-348, August 2013. Download Full Issue. Download started. Ok. PDF [532 KB] PDF [532 KB] Figures. Figure Viewer; Download Figures (PPT)
Green Tea and Its Relation to Human Gut Microbiome
1. Introduction. Tea is a beverage that is thousands of years old and has not lost its popularity due to different health benefits, pleasantness, or social characteristics [1,2,3].Made from the infusion of the leaves of the Camellia sinensis plant, tea has been used in traditional Chinese medicine for over 3000 years [2,4].Tea has expanded over the centuries from China throughout the rest of ...
Enhancing the flavor profile of strong-flavored green tea from Sichuan
The flavor of the collected green tea samples was evaluated. The QDA method was used to obtain the scores of the seven taste subfactors (freshness, sweetness, bitterness, astringency, strength, thickness, and harmony) for each sample (Table S5).To classify green tea samples by flavor, k-means clustering was used on the 64 samples based on the tast subfactors.
10 Evidence-Based Benefits of Green Tea
A 2017 research paper found that drinking green tea may benefit cognition, mood, and brain function, possibly due to compounds in green tea like caffeine and L-theanine.. A 2020 study also ...
Nutrients
A common feature of such damage is drugs, which allows it to be defined as drug-induced liver injury (DILI). In this review, we analysed available research findings in the global literature regarding the effects of green tea and/or its phenolic compounds on liver function in the context of protective action during prolonged exposure to xenobiotics.
The green tea effect: From gut microbes to weight loss, new insights emerge
Green tea, consumed widely, is known to have beneficial effects such as reducing body weight and metabolic syndrome. Its components - polyphenols, caffeine (Caf), and L-theanine (Thea), can ...
Beneficial effects of green tea: A literature review
The health benefits of green tea for a wide variety of ailments, including different types of cancer, heart disease, and liver disease, were reported. Many of these beneficial effects of green tea are related to its catechin, particularly (-)-epigallocatechin-3-gallate, content. There is evidence from in vitro and animal studies on the underlying mechanisms of green tea catechins and their ...
Green tea is known for its health benefits
Don't kettle for just any source of caffeine — green tea has its health benefits, but it could also make you happier. Previous research has shown the positive quali-teas of the drink, such as ...
Turmeric and green tea among six supplements putting people in hospital
New research has revealed the extent of the damage being caused by taking popular botanical supplements including turmeric, green tea, the stress-relieving ashwagandha and weight-loss aid Garcinia ...
Research Shows This Super Popular Drink Offers Metabolic & Cognitive
The tea strainer helps get rid of clumps. Add boiled water and cool it to 80-90℃ (176-194°F). Pour 30-40ml of hot water into matcha in the tea bowl. Whisk the tea until you don't see any clumps. A bamboo whisk is better, but use a spoon or frother if you don't have it. If you still see clumps, strain the tea one more time with the tea strainer.
Popular health supplements causing liver damage, hospitalizations
Research has revealed the extent of the damage being caused by taking popular botanical supplements including turmeric, green tea, the stress-relieving ashwagandha and weight-loss aid Garcinia ...
Therapeutic effects of green tea as an antioxidant on oral health- A
Gingivitis and periodontitis. Green tea has been reported to be useful for prevention of periodontal disease progression. Several in vitro studies have shown that the growth of porphyromonas gingivalis, prevotella intermedia and prevotella nigrescens on human buccal epithelial cells is inhibited by the green tea component EGCG.[7,8] These bacteria are heavily involved in the destruction of ...
How 'green' electricity from wood harms the planet
The town of Hamlet, North Carolina, seemed to hit the jackpot in September 2014. After the community had endured decades of economic despair and high poverty rates, the world's largest producer ...
I'm from Japan, home to some of the world's longest living people: 8
Nutritionist and longevity expert Michiko Tomioka shares the foods she always eats to promote longevity, inspired by her experiences growing up in Nara, Japan.
COVID booster vaccines get green light from FDA : Shots
The Food and Drug Administration Thursday gave the green light to two updated COVID-19 vaccines to help people ... director of the FDA's Center for Biologics Evaluation and Research in a statement ...
Tea and Health: Studies in Humans
In humans, plasma bioavailability of green tea catechins is very low. After the administration of either 697 mg of green tea or 547 mg of black tea to healthy volunteers, plasma EGC and EC content was 0.26-0.75% compared with EGCG and ECG with 0.07-0.20% with similar observations in urine [ 9 ].
Federal government grants first floating offshore wind power research
PORTLAND, Maine (AP) — The federal government issued on Monday the nation's first floating offshore wind research lease to the state of Maine, comprising about 23 square miles (60 square kilometers) in federal waters.. The state requested the lease from the federal Bureau of Ocean Energy Management for a floating offshore wind research array with up to a dozen turbines capable of ...

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Effects of green tea consumption on glycemic control: a systematic review and meta-analysis of randomized controlled trials

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