Green Tea Extract Supplementation Research Articles

The Effect of Green Tea and Sour Tea (Hibiscus sabdariffa L.) Supplementation on Oxidative Stress and Muscle Damage in Athletes

ABSTRACTObjective: Additional oxygen consumption during intense exercises may lead to oxidative stress and contribute to muscular fatigue. Green tea and sour tea (Hibiscus sabdariffa L.), which contain various flavonoids and polyphenols, have many healthful properties such as anticarcinogenic, anti-inflammatory, and heart protecting effects. The aim of the present study was to assess the effects of green tea and sour tea supplementation on oxidative stress and muscle damage in soccer athletes. Methods: This randomized, double-blind control trial was conducted on 54 male soccer players. Participants were randomly assigned to three groups to receive: 450 mg/d green tea extract (GTE) in the first group (n = 18), 450 mg/d sour tea extract (STE) in the second group (n = 18) and 450 mg/d maltodextrin in the control group (n = 18). Fasting whole blood samples were taken under resting conditions at the beginning and the end of the study to quantify the serum levels of muscle damage indices, aspartate aminotransferase (AST), creatine kinase (CK), lactate dehydrogenase (LDH), and oxidative stress biomarkers, malondialdehyde (MDA), and total antioxidant capacity (TAC). Results: After six weeks intervention, athletes who received GTE and STE supplements compared with the placebo had a significantly decreased MDA level (P = 0.008). Furthermore, STE supplementation resulted in a significant increase in TAC level compared with GTE and placebo groups (P = 0.01). However, supplementation with GTE and STE had no significant effects on muscle damage indices. Conclusion: GTE and STE supplementation have beneficial effects on oxidative stress status in male athletes. However, both kinds of tea extract did not affect muscle damage status.

Green tea extract does not affect exogenous glucose appearance but reduces insulinemia with glucose ingestion in exercise recovery.

We reported that supplementation with green tea extract (GTE) lowered the glycemic response to an oral glucose load following exercise, but via an unknown mechanism (Martin BJ, MacInnis MJ, Gillen JB, Skelly LE, Gibala MJ. Appl Physiol Nutr Metab 41: 1057-1063, 2016. Here we examined the effect of supplementation with GTE on plasma glucose kinetics on ingestion of a glucose beverage during exercise recovery. Eleven healthy, sedentary men (21 ± 2 yr old; body mass index = 23 ± 4 kg/m2, peak O2 uptake = 38 ± 7 ml·kg-1·min-1; means ± SD) ingested GTE (350 mg) or placebo (PLA) thrice daily for 7 days in a double-blind, crossover design. In the fasted state, a primed constant infusion of [U-13C6]glucose was started, and 1 h later, subjects performed a graded exercise test (25 W/3 min) on a cycle ergometer. Immediately postexercise, subjects ingested a 75-g glucose beverage containing 2 g of [6,6-2H2]glucose, and blood samples were collected every 10 min for 3 h of recovery. The rate of carbohydrate oxidation was lower during exercise after GTE vs. PLA (1.26 ± 0.34 vs. 1.48 ± 0.51 g/min, P = 0.04). Glucose area under the curve (AUC) was not different between treatments after drink ingestion (GTE = 1,067 ± 133 vs. PLA = 1,052 ± 91 mM/180 min, P = 0.91). Insulin AUC was lower after GTE vs. PLA (5,673 ± 2,153 vs. 7,039 ± 2,588 µIU/180 min, P = 0.05), despite similar rates of glucose appearance (GTE = 0.42 ± 0.16 vs. PLA = 0.43 ± 0.13 g/min, P = 0.74) and disappearance (GTE = 0.43 ± 0.14 vs. PLA = 0.44 ± 0.14 g/min, P = 0.57). We conclude that short-term GTE supplementation did not affect glucose kinetics following ingestion of an oral glucose load postexercise; however, GTE was associated with attenuated insulinemia. These findings suggest GTE lowers the insulin required for a given glucose load during postexercise recovery, which warrants further mechanistic studies in humans.

Green tea extract and catechol-O-methyltransferase genotype modify the post-prandial serum insulin response in a randomised trial of overweight and obese post-menopausal women.

Green tea extract (GTE) may be involved in a favourable post-prandial response to high-carbohydrate meals. The catechol-O-methyltransferase (COMT) genotype may modify these effects. We examined the acute effects of GTE supplementation on the post-prandial response to a high-carbohydrate meal by assessing appetite-associated hormones and glucose homeostasis marker concentrations in women who consumed 843mg of (-)-epigallocatechin-3-gallate (EGCG) or placebo capsules for 11-12months. Sixty Caucasian post-menopausal women (body mass index≥25.0kgm-2 ) were included in a randomised, double-blind feeding study. GTE was consumed with a breakfast meal [2784.0kJ (665.4kcal); 67.2% carbohydrate]. Blood samples were drawn pre-meal, post-meal, and every 30min for 4h. Participants completed six satiety questionnaires. Plasma leptin, ghrelin and adiponectin did not differ between GTE and placebo at any time point; COMT genotype did not modify these results. Participants randomised to GTE with the high-activity form of COMT (GTE-high COMT) had higher insulin concentrations at time 0, 0.5 and 1.0h post-meal compared to all COMT groups randomised to placebo. Insulin remained higher in the GTE-high COMT group at 1.5, 2.0 and 2.5h compared to Placebo-low COMT (P<0.02). GTE-high COMT had higher insulin concentrations at times 0, 0.5, 1.0, 1.5 and 2.0h compared to the GTE-low COMT (P≤0.04). Area under the curve measurements of satiety did not differ between GTE and placebo. GTE supplementation and COMT genotype did not alter acute post-prandial responses of leptin, ghrelin, adiponectin or satiety, although it may be involved in post-meal insulinaemic response of overweight and obese post-menopausal women.

Prolonged feeding with green tea polyphenols exacerbates cholesterol-induced fatty liver disease in mice

This study investigated the potential deleterious impact of dietary supplementation with green tea extract (GTE) on the progression of fatty liver disease, in a mouse model of cholesterol-induced steatohepatitis that represents chronic liver injury. Male C57BL mice (n = 32, 8-wk-old) were fed for 6 wk with one of the following diets: normal control diet (ND, Con), Con + 1% w/w polyphenols from GTE (Con + GTE); high cholesterol diet, Con + 1% cholesterol + 0.5% cholate w/w (HCD); HCD + 1% green tea polyphenols w/w (HCD + GTE). Hepatic steatosis, oxidative, and inflammatory markers and bile acid synthesis pathways were measured. HCD supplementation resulted in hepatic steatosis and liver damage. In animals supplemented with the HCD + GTE an exacerbated hepatic steatosis, oxidative stress, and inflammatory response were observed compared to HCD supplemented animals. HCD + GTE supplementation elevated blood levels of liver enzymes and serum bile acids compared HCD-treated animals. HCD + GTE supplementation altered bile acid synthesisin thecholesterol clearance pathway, inducing a shift from the classically regulated CYP7A1 pathway to the alternative acidic pathway. Prolonged GTE supplementation dramatically increased hepatic oxidative stress, inflammation and liver injury, and altered the bile acid synthesis pathway in mice fed a HCD.

Short-term green tea extract supplementation attenuates the postprandial blood glucose and insulin response following exercise in overweight men.

Green tea extract (GTE) ingestion improves glucose homeostasis in healthy and diabetic humans, but the interactive effect of GTE and exercise is unknown. The present study examined the effect of short-term GTE supplementation on the glycemic response to an oral glucose load at rest and following an acute bout of exercise, as well as substrate oxidation during exercise. Eleven sedentary, overweight men with fasting plasma glucose (FPG) ≥5.6 mmol·L-1 (age, 34 ± 13 years; body mass index = 32 ± 5 kg·m-2; FPG = 6.8 ± 1.0; mean ± SD) ingested GTE (3× per day, 1050 mg·day-1 total) or placebo (PLA) for 7 days in a double-blind, crossover design. The effects of a 75-g glucose drink were assessed on 4 occasions during both GTE and PLA treatments: On days 1 and 5 at rest, and again following an acute bout of exercise on days 3 and 8. The glycemic response was assessed via an indwelling continuous glucose monitor (CGM) and venous blood draws. At rest, 1-h CGM glucose area under the curve was not different (P > 0.05), but the postexercise response was lower after GTE versus PLA (330 ± 53 and 393 ± 65 mmol·L-1·min-1, main effect of treatment, P < 0.05). The 1-h postprandial peaks in venous blood glucose (8.6 ± 1.6 and 9.8 ± 2.2 mmol·L-1) and insulin (96 ± 59 and 124 ± 68 μIU·ml-1) were also lower postexercise with GTE versus PLA (time × treatment interactions, P < 0.05). In conclusion, short-term GTE supplementation did not affect postprandial glucose at rest; however, GTE was associated with an attenuated glycemic response following a postexercise oral glucose load. These data suggest that GTE might alter skeletal muscle glucose uptake in humans.

Green Tea Extract Supplementation Modifies Circulating Lipids in Postmenopausal Women: A Randomized, Placebo‐Controlled Clinical Trial

BackgroundGreen tea has been suggested to improve cardiovascular risk factors including circulating lipid parameters predominantly based on small and short randomized controlled trials. Data from long‐term intervention studies with relatively large sample size are lacking.ObjectiveTo determine the effects of daily green tea extract (GTE) supplementation high in epigallocatechin gallate (EGCG) for 12 months on blood lipids in healthy postmenopausal women in U.S.Methods and designThis was an ancillary study carried out as part of a phase II randomized, double‐blind, placebo‐controlled trial to investigate the effects of GTE supplementation containing 843 mg EGCG on breast cancer risk biomarkers. Subjects were randomized to either the GTE (n= 538) or placebo (n= 537) group, and 936 women completed the one‐year intervention. Participants were healthy postmenopausal women (mean age of 59.8 ± 5.0 years), mainly non‐Hispanic white (97%), who did not regularly consume tea (&lt;1 cup/week) or currently smoked cigarettes (31% former smokers), and had mean body mass index (BMI) of 25.1 ± 3.7 kg/m2. Each woman took 2 capsules of GTE or placebo twice daily for one year. Total cholesterol (TC), high‐density lipoprotein cholesterol (HDL‐C) and triglycerides (TG) were measured using spectrophotometry in fasting serum samples at baseline, month 6 and month 12. Levels of low‐density lipoprotein cholesterol (LDL‐C), non‐HDL cholesterol and the ratio of TC to HDL‐C were calculated. Participants provided information on demographic characteristics, lifestyle factors, and diet history at baseline. The repeated measures ANCOVA adjusted for age and BMI at baseline was used for calculating the mean change of circulating lipids for placebo and GTE treatment groups and testing for the differences between two groups.ResultsOne‐year supplementation with GTE capsules resulted in significant reduction of circulating TC (by 2.1%), LDL‐C (by 4.1%) and non‐HDL‐C (by 3.1%) (all Ps &lt;0.001). The maximum reductions were observed in month 6. There was no change in HDL‐C concentration, but TG levels increased by 3.6% in GTE group compared with placebo group (P = 0.01). A significant reduction in TC was only observed among women with high (i.e. ≥200 mg/dL) baseline TC levels (P for interaction= 0.01), and those who did not use the cholesterol‐lowering drug statin. The effect of GTE on the increase in TG was confined to obese women (P for interaction = 0.06), and those with low baseline TG (i.e. &lt;150 mg/dL).ConclusionsAmong healthy postmenopausal women, supplementation with GTE significantly reduced circulating TC and LDL‐C levels, especially in those with elevated baseline TC levels without use of lipid lowering drug statin. These novel findings suggest that GTE can be developed as a potential cholesterol lowering agent, especially for those who are intolerant to statin.Support or Funding InformationThis work was funded by the National Institute of Health (R01 CA127236) and the Department of Defense (W81XWH‐11‐1‐0013).

Long-Term Supplementation of Green Tea Extract Does Not Modify Adiposity or Bone Mineral Density in a Randomized Trial of Overweight and Obese Postmenopausal Women

Background: Green tea extract (GTE) consumption has been linked to favorable changes in adiposity and bone mineral density (BMD), although it is unknown if these effects are due to green tea catechins or caffeine. The catechol-O-methyltransferase (COMT) genotype may also modify these associations.Objective: We examined the impact of decaffeinated GTE on body composition (using dual-energy X-ray absorptiometry) and obesity-associated hormones.Methods: The Minnesota Green Tea Trial was a 12-mo randomized, double-blind, placebo-controlled clinical trial in 937 postmenopausal women (aged 50–70 y) assigned to receive either GTE containing 843 mg (−)-epigallocatechin-3-gallate or placebo. This substudy was conducted in 121 overweight/obese participants [body mass index (BMI) (kg/m2) ≥25.0].Results: There were no differences in changes in BMI (−0.13 ± 0.11 compared with −0.05 ± 0.11; P = 0.61), total fat mass (−0.30 ± 0.16 compared with −0.12 ± 0.15 kg; P = 0.40), percentage of body fat (−0.15% ± 0.17% compared with −0.15% ± 0.16%; P = 0.99), or BMD (−0.006 ± 0.002 compared with −0.003 ± 0.002 g/cm2; P = 0.49) over 12 mo between women taking GTE (n = 61) and those taking a placebo (n = 60). Interactions were observed between treatment and time for gynoid percentage of fat (%fat) and tissue %fat. Gynoid %fat increased from baseline to month 12 in the placebo group as baseline BMI increased and decreased over time as baseline BMI increased in the GTE group (P-interaction = 0.02). Tissue %fat increased from baseline to month 12 in the placebo group as baseline BMI increased. In the GTE group, tissue %fat decreased during the intervention as baseline BMI increased (P-interaction = 0.04). No changes were seen in circulating leptin, ghrelin, adiponectin, or insulin concentrations. COMT genotype did not modify the effect of GTE on any variable.Conclusions: Decaffeinated GTE was not associated with overall reductions in adiposity or improvements in BMD in overweight/obese postmenopausal women. However, GTE may be beneficial for reduction in tissue and gynoid %fat in individuals with higher BMI. This clinical trial was registered at www.clinicaltrials.gov as NCT00917735.

The Effect of Green Tea (Camellia sinensis) Extract Against Hepato-Toxicity Induced By Tamoxifen in Rats

The present study was conducted to elucidate the antioxidant capacity of green tea (Camellia sinensis) extract against Tamoxifen citrate-induced liver injury. Four groups containing ten female Wister rats each were selected: Group I, served as control group, Group II, permitted Green Tea Extract (1.5% w/v in water) as the sole drinking fluid, Group III, injured by intraperitoneal injection of Tamoxefin (45 mg/ Kg/day) for 7 successive days and Group IV, permitted green tea extract as a sole source of drinking water (1.5% w/v in water) 4 days prior and 14 days after Tamxifen-intoxication (45 mg/Kg/day for 7 successive days). Hepatic oxidative damage was observed in Tamoxefin treated rats as evidenced via augmentation in liver lipid peroxidation as well as depletion in liver antioxidant enzymes; catalase, superoxide dismutase and glutathione peroxidase with highly degeneration and necrosis of the hepatocytes. Histopathological studies of liver treated with Tamoxefin revealed that supplementation of green tea extract resulted in mild degeneration and necrosis of the hepatocytes. Furthermore, green tea extract had normalized catalase, superoxide dismutase, glutathione peroxidase and liver lipid peroxidation content. In Conclusion, the supplementation of green tea extract appeared to be beneficial to a great extent in attenuating and restoring the damage sustained by Tamoxefin exposure.

Dietary effect of green tea extract on hydration improvement and metabolism of free amino acid generation in epidermis of UV-irradiated hairless mice

Purpose: Ultraviolet (UV) irradiation decreases epidermal hydration, which is maintained by reduction of natural moisturizing factors (NMFs). Among various NMFs, free amino acids (AA) are major constituents generated by filaggrin degradation. This experiment was conducted to determine whether or not dietary supplementation of green tea extract (GTE) in UV-irradiated mice can improve epidermal levels of hydration, filaggrin, free AAs, and peptidylarginine deiminase-3 (PAD3) expression (an enzyme involved in filaggrin degradation). Methods: Hairless mice were fed a diet of 1% GTE for 10 weeks in parallel with UV irradiation (group UV+1%GTE). As controls, hairless mice were fed a control diet in parallel with (group UV+) or without (group UV-) UV irradiation. Results: In group UV+, epidermal levels of hydration and filaggrin were lower than those in group UV-; these levels increased in group UV+1% GTE to levels similar to group UV-. Epidermal levels of PAD3 and major AAs of NMF, alanine, glycine and serine were similar in groups UV- and UV+, whereas these levels highly increased in group UV+1% GTE. Conclusion: Dietary GTE improves epidermal hydration by filaggrin generation and degradation into AAs.

The Effect of Green Tea Extract Supplementation on Liver Enzymes in Patients with Nonalcoholic Fatty Liver Disease.

Background:Green tea is one of the most popular beverages in the world. It is believed to have beneficial effects in the prevention and treatment of many diseases, one of which is nonalcoholic fatty liver disease (NAFLD). The present study investigated the effects of consumption of green tea in NAFLD patients.Methods:This study was a double-blind, placebo-controlled, randomized clinical trial. Ultrasonography was used to diagnose fatty liver in patients with alanine aminotransferase (ALT) >31 mg/dl and 41 mg/dl and aspartate aminotransferase (AST) >31 mg/dl and 47 g/dl in women and men, respectively and without other hepatic diseases. A total of 80 participants (20–50 years) with NAFLD were randomly allocated into two groups to receive either green tea extract (GTE) supplement (500 mg GTE tablet per day) or placebo for 90 days. At baseline and at the end of the intervention weight, serum ALT, AST, and alkaline phosphatase (ALP) were measured in fasting state, and dietary data were collected at baseline and end of the study.Results:Green tea group showed significant reductions in ALT and AST levels after 12 weeks period (P < 0.001). The placebo group showed a reduction in ALT and AST levels at the end of the study, but it was no significant. ALP levels showed significant reductions in both groups after 12 weeks period (P < 0.001).Conclusions:According to the findings of this study, GTE supplementation decrease liver enzymes in patients with NAFLD. It can be claimed that GTE prescribed can be considered as a treatment to improve serum levels of liver enzymes in NAFLD patients.

Dietary effect of green tea extract on epidermal levels of skin pH related factors, lactate dehydrogenase protein expression and activity in UV-irradiated hairless mice

Purpose: Skin pH, an indicator of skin health, is maintained by various organic factors, which include lactate, free amino acid (FAA), and free fatty acid (FFA). As skin ages or with illness, skin pH becomes less acidic, and functional food has been developed to maintain the acidic pH of skin. In this study, we determined the dietary effect of green tea extract (GTE) on skin pH of photo-aged mice, as measured by epidermal levels of lactate, FAA, and FFA. The protein expression and activity of lactate dehydrogenase (LDH), an enzyme of pyruvate reduction for lactate generation, was further determined. Methods: Albino hairless mice were fed a control diet (group UV+) or a diet with 1% GTE (group GTE) in parallel with UV irradiation for 10 weeks. A normal control group was fed a control diet without UV irradiation for 10 weeks (group UV-). Results: Skin pH was higher (less acidic) in group UV+ than in group UV-. In parallel, epidermal levels of lactate and FFA, as well as of LDH protein expression and activity, were reduced in group UV+. Dietary supplementation of GTE (group GTE) reduced skin pH to similar to the level of group UV-, and inversely increased epidermal levels of lactate, LDH protein expression and activity, but not of FFA. Although epidermal levels of FAA were similar in groups UV- and UV+, it was increased in group GTE to a level higher than in group UV-. In further analysis of major FFA, epidermal levels of palmitic acid [16:0], oleic acid [18:1(n-9)], and linoleic acid [18:2(n-6), but not of stearic acid [18:0] in group GTE were similar to or lower than those in group UV+. Conclusion: Dietary GTE normalized skin pH with increased levels of lactate and FAA, as well as with increased protein expression and activity of LDH in the epidermis of UVB irradiated hairless mice.

The Peroxidation of Leukocytes Index Ratio Reveals the Prooxidant Effect of Green Tea Extract.

Despite tea increased plasma nonenzymatic antioxidant capacity, the European Food Safety Administration (EFSA) denied claims related to tea and its protection from oxidative damage. Furthermore, the Supplement Information Expert Committee (DSI EC) expressed some doubts on the safety of green tea extract (GTE). We performed a pilot study in order to evaluate the effect of a single dose of two capsules of a GTE supplement (200 mg × 2) on the peroxidation of leukocytes index ratio (PLIR) in relation to uric acid (UA) and ferric reducing antioxidant potential (FRAP), as well as the sample size to reach statistical significance. GTE induced a prooxidant effect on leukocytes, whereas FRAP did not change, in agreement with the EFSA and the DSI EC conclusions. Besides, our results confirm the primary role of UA in the antioxidant defences. The ratio based calculation of the PLIR reduced the sample size to reach statistical significance, compared to the resistance to an exogenous oxidative stress and to the functional capacity of oxidative burst. Therefore, PLIR could be a sensitive marker of redox status.

Abstract CT111: Green tea extract supplementation, estrogen metabolism and breast cancer risk in postmenopausal women at high risk of breast cancer

Abstract Background: Green tea intake may be associated with reduced risk of several cancers including breast cancer. One of the proposed mechanisms by which green tea may modify breast cancer risk is through effects on estrogen metabolism. Genetic variation in catechol-O-methyltransferase (COMT), an enzyme involved in the metabolism of both estrogens and tea catechins, may also have a role. Few studies have examined the effects of green tea intake on circulating and urinary estrogens and estrogen metabolites, and even less is known about the potential modifying influence of polymorphisms in the COMT gene. Objectives: To investigate the effects of daily intake of a highly concentrated green tea extract (GTE) for one year on circulating and urinary estrogens and their metabolites in postmenopausal women with different COMT genotypes. Methods: The Minnesota Green Tea Trial (MGTT), a randomized, double-blind, placebo-controlled, phase II clinical trial, enrolled 1075 healthy postmenopausal women with heterogeneously or extremely dense breast tissue (age = 59.78 ± 5.02 years; body mass index = 25.70 ± 8.21 kg/m2). Participants were 93% non-Hispanic white and non-current hormone users. Half of the participants (n = 538) were randomly assigned to the GTE group and were given 4 capsules a day, each containing 200 mg epigallocatechin gallate (EGCG) and the others (n = 537) to the placebo group. Twenty-four hour urine samples were collected at month 0 and at the end of the study, and fasting blood samples were drawn at months 0, 6 and 12. Circulating and urinary estrogens, as well as urinary estrogen metabolites were quantified by liquid chromatography-tandem mass spectrometry. Results: GTE supplementation was associated with reduced urinary estriol (-10.7%, P = 0.08) and 2-methoxy estrone (-12.2%, P = 0.014) compared with baseline, and these changes were significantly greater than the corresponding changes in the placebo group (P = 0.003, and P = 0.02, respectively). GTE supplementation had no significant effects on serum or urinary estrone and estradiol. Among women with the low activity COMT genotype, GTE supplementation reduced urinary estrone (-5.3%) compared with women with high activity COMT (+2.1%) (between groups comparison P = 0.049). Statistical analyses are ongoing to examine the potential modifying effects of COMT genotype on other urinary estrogen metabolites. Conclusion: Daily intake of high-dose green tea extract for 12 months exerts significant effects on urinary excretion of estrogen metabolites, and these effects may be modified by COMT polymorphisms. The potential beneficial effects of green tea extract on estrogen metabolism support the further development of green tea as a potential chemopreventive agents for estrogen-related disease prevention. Funding source: NIH/NCI (R01 CA127236). Citation Format: Hamed Samavat, Renwei Wang, Anna Wu, Jian-Min Yuan, Mindy Kurzer. Green tea extract supplementation, estrogen metabolism and breast cancer risk in postmenopausal women at high risk of breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT111. doi:10.1158/1538-7445.AM2015-CT111

The safety of green tea extract supplementation in postmenopausal women at risk for breast cancer: results of the Minnesota Green Tea Trial

Green tea is thought to provide health benefits, though adverse reactions to green tea extract (GTE) have been reported. We conducted a randomized, double-blind, placebo-controlled study of GTE on breast cancer biomarkers, including mammographic density, in which 1075 postmenopausal women were randomly assigned to consume GTE containing 843 mg (-)-epigallocatechin-3-gallate (EGCG) or placebo daily for one year. There were no significant differences in % of women with adverse events (AEs, 75.6% and 72.8% of the GTE group and placebo group, respectively) or serious AEs (2.2 % and 1.5% of GTE and placebo groups, respectively). Women on GTE reported significantly higher incidence of nausea (P < 0.001) and dermatologic AEs (P = 0.05) and significantly lower diarrhea incidence (P = 0.02). More women in the GTE group experienced an alanine aminotransferase (ALT) elevation compared with placebo group (n = 36, (6.7%) vs. n = 4, (0.7%); P < 0.001). There were no statistically significant differences between groups in frequencies of other AEs. Overall, AEs were mainly mild and transient, indicating that daily consumption of GTE containing 843 mg EGCG is generally well tolerated by a group of predominantly Caucasian postmenopausal women. However, 6.7% of GTE consumers experienced ALT elevations, with 1.3% experiencing ALT-related serious AEs.

Green tea extract supplementation does not hamper endurance-training adaptation but improves antioxidant capacity in sedentary men.

The purpose of this study was to investigate the effect of green tea extract (GTE) supplementation combined with endurance training on endurance capacity and performance in sedentary men. Forty untrained men (age: 20 ± 1 years) participated in this study. Subjects were assigned to 1 of 4 treatments: (i) placebo-control (CTRL), (ii) GTE, (iii) endurance training (Ex), and (iv) endurance training with GTE (ExGTE). During the 4-week intervention, exercise training was prescribed as 75% oxygen uptake reserve for three 20-min sessions per week, and either GTE (250 mg/day) or placebo was provided. Endurance capacity, malondialdehyde (MDA), total antioxidant status (TAS), and creatine kinase (CK) were examined. Ex and ExGTE but not GTE improved exhaustive-run time (Ex: +8.2%, p = 0.031; ExGTE: +14.3%, p < 0.001); in addition, Ex and ExGTE significantly increased maximal oxygen uptake by ∼14% (p = 0.041) and ∼17% (p = 0.017) above the values of the CTRL group, respectively. Both Ex and ExGTE significantly decreased the increase of CK by ∼11%-32% below that of CTRL following an exhaustive run (Ex: p = 0.007; ExGTE: p = 0.001). Moreover, TAS levels increased by ∼11% in ExGTE after training (p = 0.040), and GTE, Ex, and ExGTE markedly attenuated exercise-induced MDA production (p = 0.01, p = 0.005, p = 0.011, respectively). In conclusion, this investigation demonstrated that daily ingestion of GTE during endurance training does not impair improvements in endurance capacity. Moreover, endurance training combined with GTE not only increases antioxidant capacity without attenuating endurance training adaptations, but also further attenuates acute exercise-induced CK release.

Long-Term Green Tea Extract Supplementation Does Not Affect Fat Absorption, Resting Energy Expenditure, and Body Composition in Adults1–3

Background: Green tea (GT) extract may play a role in body weight regulation. Suggested mechanisms are decreased fat absorption and increased energy expenditure.Objective: We examined whether GT supplementation for 12 wk has beneficial effects on weight control via a reduction in dietary lipid absorption as well as an increase in resting energy expenditure (REE).Methods: Sixty Caucasian men and women [BMI (in kg/m2): 18–25 or >25; age: 18–50 y] were included in a randomized placebo-controlled study in which fecal energy content (FEC), fecal fat content (FFC), resting energy expenditure, respiratory quotient (RQ), body composition, and physical activity were measured twice (baseline vs. week 12). For 12 wk, subjects consumed either GT (>0.56 g/d epigallocatechin gallate + 0.28–0.45 g/d caffeine) or placebo capsules. Before the measurements, subjects recorded energy intake for 4 consecutive days and collected feces for 3 consecutive days.Results: No significant differences between groups and no significant changes over time were observed for the measured variables. Overall means ± SDs were 7.2 ± 3.8 g/d, 6.1 ± 1.2 MJ/d, 67.3 ± 14.3 kg, and 29.8 ± 8.6% for FFC, REE, body weight, and body fat percentage, respectively.Conclusion: GT supplementation for 12 wk in 60 men and women did not have a significant effect on FEC, FFC, REE, RQ, and body composition. This trial was registered at clinicaltrials.gov as NCT01556321.

The study of the anti‐obesity effect of dairy administration green tea extract in high fat diet induced obese rats

In the previous researches, several anti-obesity mechanisms were described such as induction of LPL expression and anti-oxidant activity. Green tea polyphenols have also been reported to have beneficial effects of against obesity. However, the mechanism is not clear. The aim of this study was to assess anti-obesity effect of green tea extract (GTE) in obese rat model. Thirty male SD rats were divided into three groups as follows: the control group (rats fed with normal diet;C group), the HE group (rats fed with high-fat diet;HE group), and the HE+GTE group (rats fed with high-fat diet and GTE by oral;HEG group). After eight weeks, body weight, feed efficiency, body composition, body fat percentage, serum biochemical tests, lipoprotein lipase (LPL) activity assays, TG and TC in liver were measured to evaluate the anti-obesity effects. GTE supplementation significantly enhanced body composition, decreased body fat percentage, and reduced the level of TG and TC in serum and liver. Furthermore,the up-regulation of LPL and antioxidant genes was observed in the GTE supplemented groups. The results revealed that the beneficial effects of GTE may via modulating LPL activity to decrease on body weight.

The Safety of Green Tea Extract Supplementation in Postmenopausal Women at Risk for Breast Cancer: Results of the Minnesota Green Tea Trial

The objective of this study was to monitor adverse events (AEs) in healthy postmenopausal women randomized to receive either green tea extract (GTE) containing 840 mg (‐)‐epigallocatechin‐3‐gallate (EGCG)/day (n=538) or placebo (n=537) for one year. Data on AEs was obtained by participant self‐report and hepatic panel assessment. AEs were recorded and graded using the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE), v.4.03. 407 participants in the GTE group reported 1141 AEs; 391 participants in the placebo group reported 1031 AEs. Infections and infestations were the most common AEs (139 GTE vs. 145 placebo participants, p = 0.67) followed by gastrointestinal (GI) disorders (137 GTE vs. 123 placebo participants, p = 0.33). Nausea incidence was higher in GTE participants (55 (10.2%) vs. 26 (4.8%), p &lt; 0.001). Diarrhea incidence was lower in the GTE group (24 (4.5%) vs. 43 (8%) participants, p = 0.02). More participants taking GTE reported dermatologic AEs (18 (3.3%) vs. 8 (1.5%), p = 0.05). Alanine aminotransferase (ALT) elevations were seen in 36 (6.7%) GTE vs. 4 (0.7%) placebo participants (p &lt; 0.001). Twenty‐six serious adverse events (CTCAE grades 3‐5) occurred in 12 GTE vs. 8 placebo participants (p = 0.37). GTE containing 840 mg EGCG/day was associated with mainly mild, transient AEs and was well tolerated by most participants, though an association with GI and hepatic abnormalities was confirmed. This project was supported by the NIH/NCI.

Body fat accumulation in zebrafish is induced by a diet rich in fat and reduced by supplementation with green tea extract.

Fat-rich diets not only induce obesity in humans but also make animals obese. Therefore, animals that accumulate body fat in response to a high-fat diet (especially rodents) are commonly used in obesity research. The effect of dietary fat on body fat accumulation is not fully understood in zebrafish, an excellent model of vertebrate lipid metabolism. Here, we explored the effects of dietary fat and green tea extract, which has anti-obesity properties, on body fat accumulation in zebrafish. Adult zebrafish were allocated to four diet groups and over 6 weeks were fed a high-fat diet containing basal diet plus two types of fat or a low-fat diet containing basal diet plus carbohydrate or protein. Another group of adult zebrafish was fed a high-fat diet with or without 5% green tea extract supplementation. Zebrafish fed the high-fat diets had nearly twice the body fat (visceral, subcutaneous, and total fat) volume and body fat volume ratio (body fat volume/body weight) of those fed low-fat diets. There were no differences in body fat accumulation between the two high-fat groups, nor were there any differences between the two low-fat groups. Adding green tea extract to the high-fat diet significantly suppressed body weight, body fat volume, and body fat volume ratio compared with the same diet lacking green tea extract. 3-Hydroxyacyl-coenzyme A dehydrogenase and citrate synthase activity in the liver and skeletal muscle were significantly higher in fish fed the diet supplemented with green tea extract than in those fed the unsupplemented diet. Our results suggest that a diet rich in fat, instead of protein or carbohydrate, induced body fat accumulation in zebrafish with mechanisms that might be similar to those in mammals. Consequently, zebrafish might serve as a good animal model for research into obesity induced by high-fat diets.

Effect of green tea supplementation on blood pressure among overweight and obese adults: a systematic review and meta-analysis.

Emerging randomized controlled trials (RCTs) investigating the effect of green tea or green tea extract (GTE) supplementation on blood pressure (BP) among overweight and obese adults reported inconsistent findings. To conduct a systematic review and meta-analysis to clarify the efficacy of green tea or GTE on BP among overweight and obese adults. Electronic databases, conference proceedings and gray literature were searched systematically to include parallel and cross-over RCTs examining the efficacy of green tea or GTE on BP compared with placebo. Data were meta-analyzed using a random-effects model, to compare the mean difference of the change in BP from baseline in the intervention and the placebo groups. Fourteen RCTs with 971 participants (47% women) were pooled for analysis. Green tea or GTE produced a significant effect on both SBP (mean difference -1.42 mmHg, 95% confidence interval -2.47 to -0.36, P = 0.008; I = 52%, P = 0.01 for heterogeneity) and DBP (mean difference -1.25 mmHg, 95% confidence interval -2.32 to -0.19, P = 0.02; I = 74%, P < 0.001 for heterogeneity), compared with placebo. The quality of evidence across studies was low. Similar results were found in subgroup and sensitivity analyses. Among overweight and obese adults, green tea or GTE supplementation is found to cause a small but significant reduction in BP. More high-quality RCTs with large sample sizes are needed to further confirm the efficacy on BP and make strong recommendations for green tea or GTE supplementation among the overweight and obese adults.