The Effects of Epigallocatechin-3-Gallate on Thermogenesis and Fat Oxidation in Obese Men: A Pilot Study Epigallocatechin-3-gallate and postprandial fat oxidation in overweight/obese male volunteers: a pilot study Phase I pharmacokinetic study of tea polyphenols following single-dose administration of epigallocatechin gallate and polyphenon E. Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and fat oxidation in men. Effects of Dosing Condition on the Oral Bioavailability of Green Tea Catechins after Single-Dose Administration of Polyphenon E in Healthy Individuals Diet supplementation with green tea extract epigallocatechin gallate prevents progression to glucose intolerance in db/db mice Role of (−)-epigallocatechin gallate in the pharmacokinetic interaction between nadolol and green tea in healthy volunteers Health effects of green tea catechins in overweight and obese men: a randomised controlled cross-over trial. Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Blood and urine levels of tea catechins after ingestion of different amounts of green tea by human volunteers. Acute ingestion of catechin-rich green tea improves postprandial glucose status and increases serum thioredoxin concentrations in postmenopausal women. Phase IIa chemoprevention trial of green tea polyphenols in high-risk individuals of liver cancer: modulation of urinary excretion of green tea polyphenols and 8-hydroxydeoxyguanosine. The effects of EGCG on fat oxidation and endurance performance in male cyclists. Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E in healthy individuals. Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics? A randomized, double-blind, and placebo-controlled clinical trial. Randomized, Placebo-Controlled Trial of Green Tea Catechins for Prostate Cancer Prevention
Objectives : The development of obesity is characterized by an increase in adipose tissue mass and by concomitant and profound changes in almost all organ functions leading to diseases such as hypertension , diabetes mellitus and coronary heart disease . 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 postpr and ial thermogenesis and fat oxidation . However , human studies investigating the metabolic effects of the most predominant tea catechin , EGCG , alone are absent . Methods : In a r and omized double blind , placebo-controlled , cross-over pilot study , six overweight men were given 300 mg EGCG/d for 2d . Fasting and postpr and ial changes in energy expenditure ( EE ) and substrate oxidation were assessed . Results : Resting EE did not differ significantly between EGCG and placebo treatments , although during the first postpr and ial monitoring phase , respiratory quotient ( RQ ) values were significantly lower with EGCG compared to the placebo . Conclusions : These findings suggest that EGCG alone has the potential to increase fat oxidation in men and may thereby contribute to the anti-obesity effects of green tea . However , more studies with a greater sample size and a broader range of age and BMI are needed to define the optimum dose Objectives : Drinking green tea is associated with many health benefits , including increased fat oxidation . We tested the hypothesis that epigallocatechin-3-gallate ( EGCG ) , the main green tea catechin , increases  fat oxidation in obese men . Methods : Ten healthy overweight/obese males ( body mass index 31.3±0.8 kg/m2 ) were studied in a r and omized , placebo-controlled , double-blind crossover trial . Study supplements were low EGCG ( 300 mg ) , high EGCG ( 600 mg ) , caffeine ( 200 mg ) , EGCG/caffeine ( 300 mg/200 mg ) or placebo and were taken orally for 3 days . At the third day of supplementation , O2 consumption and CO2 production was measured by indirect calorimetry to assess energy expenditure and fat oxidation over 4 h each after overnight fasting and after a st and ardized test meal . Results : Energy expenditure was not affected by any supplementation , neither after overnight fasting nor after the test meal . During the first 2 h after overnight fasting , fat oxidation increased by 7.7 ( not significant , NS ) , 15.2 ( NS ) , 26.3 ( P<0.05 vs placebo ) and 35.4 % ( P<0.01 vs placebo and low EGCG ) , for low EGCG , high EGCG , caffeine and EGCG/caffeine , respectively . During the first 2 h after the meal , the mean increase in fat oxidation was 33.3 ( P<0.05 vs placebo ) , 20.2 ( NS ) , 34.5 ( P<0.05 vs placebo ) and 49.4 % ( P<0.05 vs placebo ) for low EGCG , high EGCG , caffeine and EGCG/caffeine , respectively . Conclusions : Low EGCG increases postpr and ial fat oxidation  in obese men and this to the same extent as 200 mg caffeine , whereas high EGCG does not exert this effect . Fasting fat oxidation is increased only by caffeine ( with or without EGCG ) . There is no synergism of low EGCG and 200 mg caffeine . Energy expenditure is not affected by EGCG Green tea has been shown to exhibit cancer-preventive activities in pre clinical studies . Its principal active components include epigallocatechin gallate ( EGCG ) , epigallocatechin ( EGC ) , epicatechin ( EC ) , and epicatechin gallate , of which EGCG is the most abundant and possesses the most potent antioxidative activity . We performed a Phase I pharmacokinetic study to determine the systemic availability of green tea catechins after single oral dose administration of EGCG and Polyphenon E ( decaffeinated green tea catechin mixture ) .  Twenty healthy subjects ( five subjects/dose level ) were r and omly assigned to one of the dose levels ( 200 , 400 , 600 , and 800 mg based on EGCG content ) . All subjects were r and omly crossed-over to receive the two catechin formulations at the same dose level . Blood and urine sample s were collected for up to 24 h after oral administration of the study medication . Tea catechin concentrations in plasma and urine sample s were determined using high-performance liquid chromatography with the coulometric electrode array detection system . After EGCG versus Polyphenon E administration , the mean area under the plasma concentration-time curves ( AUC ) of unchanged EGCG were 22.5 versus 21.9 , 35.4 versus 52.2 , 101.9 versus 79.7 , and 167.1 versus 161.4 min x microg/ml at the 200- , 400- , 600- , and 800-mg dose levels , respectively . EGC and EC were not detected in plasma after EGCG administration and were present at low/undetectable levels after Polyphenon E administration . High concentrations of EGC and EC glucuronide/sulfate conjugates were found in plasma and urine sample s after Polyphenon E administration . There were no significant differences in the pharmacokinetic characteristics of EGCG between the two study medications . The AUC and maximum plasma concentration ( Cmax ) of EGCG after the 800-mg dose of EGCG were found to be significantly higher than those after the 200- and 400-mg dose . The AUC and Cmax of EGCG after the 800-mg dose of Polyphenon E were significantly higher than those after the three lower doses . We conclude that the two catechin formulations result ed in similar plasma EGCG levels . EGC and EC were present in the body after the Polyphenon E administration ; however , they were present predominantly in conjugated forms . The systemic availability of EGCG increased at higher doses , possibly due to saturable presystemic elimination of orally administered green tea polyphenols It has been reported that green tea has a thermogenic effect , due to its caffeine content and probably also to the catechin , epigallocatechin-3-gallate ( EGCG ) . The main aim of the present study was to compare the effect of a mixture of green tea and Guarana extracts containing a fixed dose of caffeine and variable doses of EGCG on 24 h energy expenditure and fat oxidation .  Fourteen subjects took part to this r and omized , placebo-controlled , double-blind , cross-over study . Each subject was tested five times in a metabolic chamber to measure 24 h energy expenditure , substrate oxidation and blood pressure . During each stay , the subjects ingested a capsule of placebo or capsules containing 200 mg caffeine and a variable dose of EGCG ( 90 , 200 , 300 or 400 mg ) three times daily , 30 min before st and ardized meals . Twenty-four hour energy expenditure increased significantly by about 750 kJ with all EGCG-caffeine mixtures compared with placebo . No effect of the EGCG-caffeine mixture was observed for lipid oxidation . Systolic and diastolic blood pressure increased by about 7 and 5 mmHg , respectively , with the EGCG-caffeine mixtures compared with placebo . This increase was significant only for 24 h diastolic blood pressure . The main finding of the study was the increase in 24 h energy expenditure with the EGCG-caffeine mixtures . However , this increase was similar with all doses of EGCG in the mixtures Purpose : Green tea has been shown to exhibit cancer-preventive activities in pre clinical studies . Its consumption has been associated with decreased risk of certain types of cancers in humans . The oral bioavailability of the major green tea constituents , green tea catechins , is low , result ing in systemic catechin levels in humans many fold less than the effective concentrations determined in in vitro systems . We conducted this clinical study to test the hypothesis that the oral bioavailability of green tea catechins can be enhanced when consumed in the absence of food . Experimental Design s : Thirty healthy volunteers were r and omly assigned to one of the following doses of Polyphenon E ( a decaffeinated and defined green tea catechin mixture ) : 400 , 800 , or 1,200 mg , based on the epigallocatechin gallate content ( 10 subjects per dose group ) . After an overnight fast , study participants took a single dose of Polyphenon E with or without a light breakfast , which consisted of one or two 4-oz muffins and a glass of water . Following a 1-week wash-out period , subjects were crossed over to take the same dose of Polyphenon E under the opposite fasting/fed condition . Tea catechin concentrations in plasma and urine sample s collected after dosing were determined by high-pressure liquid chromatography analysis . Results : Consistent with previous reports , epigallocatechin gallate and epicatechin gallate were present in plasma mostly as the free form , whereas epicatechin and epigallocatechin were mostly present as the glucuronide and sulfate conjugates . There was > 3.5-fold increase in the average maximum plasma concentration of free epigallocatechin gallate when Polyphenon E was taken in the fasting condition than when taken with food . The dosing condition led to a similar change in plasma-free epigallocatechin and epicatechin gallate levels . Taking Polyphenon E in the fasting state did not have a significant effect on the plasma levels of total ( free and conjugated ) epigallocatechin , but result ed in lower plasma levels of total epicatechin . Urinary epigallocatechin gallate and epicatechin gallate levels were very low or undetectable following Polyphenon E administration with either dosing condition . Taking Polyphenon E under the fasting state result ed in a significant decrease in the urinary recovery of total epigallocatechin and epicatechin .  Polyphenon E administered as a single dose over the dose range studied was generally well-tolerated by the study participants . Mild and transient nausea was noted in some of the study participants and was seen most often at the highest study agent dose ( 1,200 mg epigallocatechin gallate ) and in the fasting condition . Conclusions : We conclude that greater oral bioavailability of free catechins can be achieved by taking the Polyphenon E capsules on an empty stomach after an overnight fast . Polyphenon E up to a dose that contains 800 mg epigallocatechin gallate is well-tolerated when taken under the fasting condition . This dosing condition is also expected to optimize the biological effects of tea catechins Background Green tea was suggested as a therapeutic agent for the treatment of diabetes more than 70 years ago , but the mechanisms behind its antidiabetic effect remains elusive . In this work , we address this issue by feeding a green tea extract ( TEAVIGO ™ ) with a high content of epigallocatechin gallate ( EGCG ) or the thiazolidinedione PPAR-γ agonist rosiglitazone , as positive control , to db/db mice , an animal model for diabetes . Methods Young ( 7 week-old ) db/db mice were r and omized and assigned to receive diets supplemented with or without EGCG or rosiglitazone for 10 weeks . Fasting blood glucose , body weight and food intake was measured along the treatment . Glucose and insulin levels were determined during an oral glucose tolerance test after 10 weeks of treatment . Pancreata were sample d at the end of the study for blinded histomorphometric analysis . Islets were isolated and their mRNA expression analyzed by quantitative RT-PCR . Results The results show that , in db/db mice , EGCG  improves glucose tolerance and increases glucose-stimulated insulin secretion . EGCG supplementation reduces the number of pathologically changed islets of Langerhans , increases the number and the size of islets , and heightens pancreatic endocrine area . These effects occurred in parallel with a reduction in islet endoplasmic reticulum stress markers , possibly linked to the antioxidative capacity of EGCG . Conclusions This study shows that the green tea extract EGCG markedly preserves islet structure and enhances glucose tolerance in genetically diabetic mice . Dietary supplementation with EGCG could potentially contribute to nutritional strategies for the prevention and treatment of type 2 diabetes Purpose The aim of the present study is to investigate a possible role of a single dose of (−)-epigallocatechin gallate ( EGCG ) , the major catechin in green tea , for the pharmacokinetic interaction between green tea and nadolol in humans . Methods In a r and omized three-phase crossover study , 13 healthy volunteers received single doses of 30 mg nadolol orally with water ( control ) , or an aqueous solution of EGCG-concentrated green tea extract ( GTE ) at low or high dose . Plasma concentrations and urinary excretion of nadolol were determined up to 48 h. In addition , blood pressure and pulse rate were monitored . In vitro transport kinetic experiments were performed using human embryonic kidney 293 cells stably expressing organic anion transporting polypeptide (OATP)1A2 to evaluate the inhibitory effect of EGCG on OATP1A2-mediated substrate transport . Results Single coadministration of low and high dose GTE significantly reduced the plasma concentrations of nadolol . The geometric mean ratios with 90 % CI for area under the plasma concentration – time curves from 0 to infinity of nadolol were 0.72 ( 0.56–0.87 ) for the low and 0.60 ( 0.51–0.69 ) for the high dose . There were no significant differences in Tmax , elimination half-life , and renal clearance between GTE and water phases . No significant changes were observed for blood pressure and pulse rate between phases . EGCG  competitively inhibited OATP1A2-mediated uptake of sulphobromophthalein and nadolol with Ki values of 21.6 and 19.4 μM , respectively . Conclusions EGCG is suggested to be a key contributor to the interaction of green tea with nadolol . Moreover , even a single coadministration of green tea may significantly affect nadolol pharmacokinetics Regular consumption of green tea may be cardioprotective . In the present study we investigated the health effects of dietary supplementation with green tea catechins and the potential modifying effect of the catechol-O-methyltransferase ( COMT ) Val/Met genotype . Subjects ( sedentary males , aged 40 - 69 years , with BMI ≥ 28 and ≤ 38 kg/m(2 ) ) were r and omly assigned to consume decaffeinated green tea extract ( DGT ; 530 mg containing about 400 mg total catechins/capsule , twice daily ) and placebo in a complete cross-over design . Ambulatory blood pressure and biomarkers of metabolic function ( cholesterol , TAG , glucose and insulin ) were measured at weeks 0 and 6 . Although a marked increase in the concentration of plasma epigallocatechin gallate ( EGCG ) , urinary epigallocatechin ( EGC ) and urinary 4'-O-methyl EGC was found after DGT treatment , no effect on blood pressure or biomarkers of metabolic function was observed . However , a period × treatment interaction ( P < 0·05 ) was detected for body-weight change . Despite a similar increase in estimated energy intake during intervention period 1 , body weight decreased by 0·64 ( sd 2·2 ) kg and increased by 0·53 ( sd 1·9 ) kg in the DGT and placebo groups , respectively ( P = 0·025 ) , suggesting a protective effect of green tea catechins on weight gain . Additionally , the COMT Val/Met genotype influenced urinary accumulation of EGC and 4'-O-methyl EGC ( P < 0·01 ) . Mean concentrations were lower in individuals homozygous for the high-activity G-allele , possibly reflecting increased metabolic flux and a more rapid conversion to downstream metabolic species , compared with individuals carrying at least one copy of the low-activity A-allele . Additional studies are needed to confirm these findings and further explore the modifying effect of genotype The green tea extract AR25 is an 80 % ethanolic dry extract st and ardized at 25 % catechins expressed as epigallocatechin gallate ( EGCG ) . In vitro , green tea extract AR25 exerts a direct inhibition of gastric and pancreatic lipases and a stimulation of thermogenesis . In an open study , the effects of extract AR25 were evaluated in moderately obese patients . After 3 months , body weight was decreased by 4.6 % and waist circumference by 4.48 % . These results suggest the green tea extract AR25 to be a natural product for the treatment of obesity , which exerts its activity by several ways : inhibition of lipases and stimulation of thermogenesis BACKGROUND Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system . OBJECTIVE We investigated whether a green tea extract , by virtue of its high content of caffeine and catechin polyphenols , could increase 24-h energy expenditure ( EE ) and fat oxidation in humans . DESIGN Twenty-four-hour EE , the respiratory quotient ( RQ ) , and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men . On 3 separate occasions , subjects were r and omly assigned among 3 treatments : green tea extract ( 50 mg caffeine and 90 mg epigallocatechin gallate ) , caffeine ( 50 mg ) , and placebo , which they ingested at breakfast , lunch , and dinner . RESULTS Relative to placebo , treatment with the green tea extract result ed in a significant increase in 24-h EE ( 4 % ; P < 0.01 ) and a significant decrease in 24-h RQ ( from 0.88 to 0.85 ; P < 0.001 ) without any change in urinary nitrogen . Twenty-four-hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo ( 40 % , P < 0.05 ) . Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines . CONCLUSIONS Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se . The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis , fat oxidation , or both The inhibitory activity of tea against tumorigenesis has been demonstrated in many animal models and has been suggested by some epidemiological studies . Such activity has generally been attributed to tea catechins . To underst and the bioavailability of tea catechins in humans , we gave 18 individuals different amounts of green tea  and measured the time-dependent plasma concentrations and urinary excretion of  tea catechins .  After taking 1.5 , 3.0 , and 4.5 g of decaffeinated green tea solids ( dissolved in 500 ml of water ) , the maximum plasma concentration ( Cmax ) of (-)-epigallocatechin-3-gallate ( EGCG ) was 326 ng/ml , the Cmax of (-)-epigallocatechin ( EGC ) was 550 ng/ml , and the Cmax of (-)-epicatechin ( EC ) was 190 ng/ml . These Cmax values were observed at 1.4 - 2.4 h after ingestion of the tea preparation . When the dosage was increased from 1.5 to 3.0 g , the Cmax values increased 2.7 - 3.4-fold , but increasing the dose to 4.5 g did not increase the Cmax values significantly , which suggested a saturation phenomenon . The half-life of EGCG ( 5.0 - 5.5 h ) seemed to be higher than the half-life of EGC or EC ( 2.5 - 3.4 h ) . EGC and EC , but not EGCG , were excreted in the urine . Over 90 % of the total urinary EGC and EC was excreted within 8 h. When the tea dosage was increased , the amount of EGC and EC excretion seemed to increase , but a clear dose-response relationship was not observed . The present study provides basic pharmacokinetic parameters of green tea catechins in humans ; these parameters may be used to estimate the levels of these compounds after drinking tea Elevated postpr and ial hyperglycaemia and oxidative stress increase the risks of type 2 diabetes and CVD . Green tea catechin possesses antidiabetic properties and antioxidant capacity . In the present study , we examined the acute and continuous effects of ingestion of catechin-rich green tea on postpr and ial hyperglycaemia and oxidative stress in healthy postmenopausal women . Participants were r and omly assigned into the  placebo ( P , n 11 ) or green tea ( GT , n 11 ) group . The GT group consumed a catechin-rich green tea ( catechins 615 mg/350 ml ) beverage per d for 4 weeks . The P group consumed a placebo ( catechins 92 mg/350 ml ) beverage per d for 4 weeks . At baseline and after 4 weeks , participants of each group consumed their design ated beverages with breakfast and consumed lunch 3 h after breakfast . Venous blood sample s were collected in the fasted state ( 0 h ) and at 2 , 4 and 6 h after breakfast . Postpr and ial glucose concentrations were 3 % lower in the GT group than in the P group ( three-factor ANOVA , group × time interaction , P < 0·05 ) . Serum concentrations of the derivatives of reactive oxygen metabolites increased after meals ( P < 0·05 ) , but no effect of catechin-rich green tea intake was observed . Conversely , serum postpr and ial thioredoxin concentrations were 5 % higher in the GT group than in the P group ( three-factor ANOVA , group × time interaction , P < 0·05 ) . These findings indicate that an acute ingestion of catechin-rich green tea has beneficial effects on postpr and ial glucose and redox homeostasis in postmenopausal women Modulation of urinary excretion of green tea polyphenols ( GTPs ) and oxidative DNA damage biomarker , 8-hydroxydeoxyguanosine ( 8-OHdG ) , were assessed in urine sample s collected from a r and omized , double-blinded and  placebo-controlled phase IIa chemoprevention trial with GTP in 124 individuals . These individuals were sero-positive for both HBsAg and aflatoxin-albumin adducts , and took GTP capsules daily at doses of 500 mg , 1000 mg or a placebo for 3 months . Twenty-four hour urine sample s were collected before the intervention and at the first and third month of the study . Urinary excretion of 8-OHdG and GTP components was measured by HPLC-CoulArray electrochemical detection . The baseline levels of 8-OHdG and GTP components among the three groups showed homogeneity ( P > 0.70 ) , and a non-significant fluctuation was observed in the placebo group over the 3 months ( P > 0.30 ) . In GTP-treated groups , epigallocatechin ( EGC ) and epicatechin ( EC ) levels displayed significant and dose-dependent increases in both the 500 mg group and 1000 mg group ( P < 0.05 ) . The 8-OHdG levels did not differ between the three groups at the 1 month collection , with medians of 1.83 , 2.08 and 1.86 ng/mg-creatinine for placebo , 500 and 1000 mg group , respectively ( P = 0.999 ) . At the end of the 3 months ' intervention , 8-OHdG levels decreased significantly in both GTP-treated groups , with medians of 2.02 , 1.03 and 1.15 ng/mg-creatinine for placebo , 500 mg and 1000 mg group , respectively ( P = 0.007 ) . These results suggest that urinary excretions of EGC and EC can serve as practical biomarkers for green tea consumption in human population s. The results also suggest that chemoprevention with GTP is effective in diminishing oxidative DNA damage Research ers have long been investigating strategies that can increase athletes ' ability to oxidize fatty acids and spare carbohydrate , thus potentially improving endurance capacity .  Green-tea extract ( epigallocatechin-3-gallate ; EGCG ) has been shown to improve endurance capacity in mice . If a green-tea extract can stimulate fat oxidation and as a result spare glycogen stores , then athletes may benefit through improved endurance performance . Eight male cyclists completed a study incorporating a 3-way crossover , r and omized , placebo-controlled , double-blinded , diet-controlled research design . All participants received 3 different treatments ( placebo 270 mg , EGCG 270 mg , and placebo 270 mg + caffeine 3 mg/kg ) over a 6-day period and 1 hr before exercise testing . Each participant completed 3 exercise trials consisting of 60 min of cycling at 60 % maximum oxygen uptake ( VO2(max ) ) immediately followed by a self-paced 40-km cycling time trial . The study found little benefit in consuming green-tea extract on fat oxidation or cycling performance , unlike caffeine , which did benefit cycling performance . The physiological responses observed during submaximal cycling after caffeine ingestion were similar to those reported previously , including an increase in heart rate  ( EGCG 147 + /- 17 , caffeine 146 + /- 19 , and placebo 144 + /- 15 beats/min ) , glucose at the 40-min exercise time point ( placebo 5.0 + /- 0.8 , EGCG 5.4 + /- 1.0 , and caffeine 5.8 + /- 1.0 mmol/L ) , and resting plasma free fatty acids and no change in the amount of carbohydrate and fat being oxidized . Therefore , it was concluded that green-tea extract offers no additional benefit to cyclists over and above those achieved by using caffeine PURPOSE Green tea and green tea polyphenols have been shown to possess cancer preventive activities in pre clinical model systems . In preparation for future green tea intervention trials , we have conducted a clinical study to determine the safety and pharmacokinetics of green tea polyphenols after 4 weeks of daily p.o . administration of epigallocatechin gallate ( EGCG ) or Polyphenon E ( a defined , decaffeinated green tea polyphenol mixture ) . In an exploratory fashion , we have also determined the effect of chronic green tea polyphenol administration on UV-induced erythema response . EXPERIMENTAL DESIGN Healthy participants with Fitzpatric skin type II or III underwent a 2-week run-in period and were r and omly assigned to receive one of the five treatments for 4 weeks : 800 mg EGCG once/day , 400 mg EGCG twice/day , 800 mg EGCG as Polyphenon E once/day , 400 mg EGCG as Polyphenon E twice/day , or a placebo once/day  ( 8 subjects/group ) . Sample s were collected and measurements performed before and after the 4-week treatment period for determination of safety , pharmacokinetics , and biological activity of green tea polyphenol treatment . RESULTS Adverse events reported during the 4-week treatment period include excess gas , upset stomach , nausea , heartburn , stomach ache , abdominal pain , dizziness , headache , and muscle pain . All of the reported events were rated as mild events . For most events , the incidence reported in the polyphenol-treated groups was not more than that reported in the placebo group . No significant changes were observed in blood counts and blood chemistry profiles after repeated administration of green tea polyphenol products . There was a > 60 % increase in the area under the plasma EGCG concentration-time curve after 4 weeks of green tea polyphenol treatment at a dosing schedule of 800 mg once daily . No significant changes were observed in the pharmacokinetics of EGCG after repeated green tea polyphenol treatment at a regimen of 400 mg twice daily . The pharmacokinetics of the conjugated metabolites of epigallocatechin and epicatechin were not affected by repeated green tea polyphenol treatment . Four weeks of green tea polyphenol treatment at the selected dose and dosing schedule did not provide protection against UV-induced erythema . CONCLUSIONS We conclude that it is safe for healthy individuals to take green tea polyphenol products in amounts equivalent to the EGCG content in 8 - 16 cups of green tea once a day or in divided doses twice a day for 4 weeks . There is a > 60 % increase in the systemic availability of free EGCG  after chronic green tea polyphenol administration at a high daily bolus dose ( 800 mg EGCG or Polyphenon E once daily ) 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 type 2 diabetes . The aim of the study is to examine the effect of a decaffeinated green tea extract ( GTE ) providing a daily dose of 856 mg of epigallocatechin gallate ( EGCG ) on obese individuals with type 2 diabetes . MATERIAL S AND METHODS The clinical trial was a r and omized , double-blind , placebo-controlled clinical trial conducted from December 2007 through November 2008 . The subjects were r and omly assigned to either receive 1,500 mg of a decaffeinated GTE or placebo daily for 16 weeks . Sixty-eight of 80 subjects , ages 20 - 65 years with BMI > 25 kg/m2 and type 2 diabetes for more than one year , completed this study .  Homeostasis model assessment for insulin resistance ( HOMA-IR ) was used as the major outcome measurement . At baseline and after 16 weeks of treatment , anthropometric measurements , fasting glucose , hemoglobin A1C percent ( HbA1C ) , hormone peptides , and plasma lipoproteins were measured from both groups . RESULTS No statistically significant differences were detected between the decaffeinated GTE and placebo groups in any measured variable . A statistically significant within-group 0.4-percent reduction in HbA1C ( from 8.4 to 8.0 % ) was observed after GTE treatment compared to baseline . Within-group comparison also revealed that the GTE group had significant reductions in waist circumference ( WC ) , HOMA-IR index , and insulin level , and a significant increase in the level of ghrelin . Within-group comparison of those in the placebo group showed a significant increase in the level of ghrelin . CONCLUSIONS This study found no statistical difference in any measured variable between the decaffeinated GTE and placebo groups ; however , there were some statistically significant within-group changes detected . More research is required to determine whether a decaffeinated GTE st and ardized for EGCG content will provide any clinical benefits in obese individuals with type 2 diabetes . Clinical Trial Registration NO : NCT00567905 Pre clinical , epidemiologic , and prior clinical trial data suggest that green tea catechins ( GTC ) may reduce prostate cancer risk . We conducted a placebo-controlled , r and omized clinical trial of Polyphenon E ( PolyE ) , a proprietary mixture of GTCs , containing 400 mg (−)-epigallocatechin-3-gallate ( EGCG ) per day , in 97 men with high- grade prostatic intraepithelial neoplasia ( HGPIN ) and /or atypical small acinar proliferation ( ASAP ) . The primary study endpoint was a comparison of the cumulative one-year prostate cancer rates on the two study arms . No differences in the number of prostate cancer cases were observed : 5 of 49 ( PolyE ) versus 9 of 48 ( placebo ) , P = 0.25 . A secondary endpoint comparing the cumulative rate of prostate cancer plus ASAP among men with HGPIN without ASAP at baseline , revealed a decrease in this composite endpoint : 3 of 26 ( PolyE ) versus 10 of 25 ( placebo ) , P < 0.024 . This finding was driven by a decrease in ASAP diagnoses on the Poly E ( 0/26 ) compared with the placebo arm ( 5/25 ) . A decrease in serum prostate-specific antigen ( PSA ) was observed on the PolyE arm [ −0.87 ng/mL ; 95 % confidence intervals ( CI ) , −1.66 to −0.09 ] . Adverse events related to the study agent did not significantly differ between the two study groups . Daily intake of a st and ardized , decaffeinated catechin mixture containing 400 mg EGCG per day for 1 year accumulated in plasma and was well tolerated but did not reduce the likelihood of prostate cancer in men with baseline HGPIN or ASAP . Cancer Prev Res ; 8(10 ) ; 879–87 . © 2015 AACR
Changes in FOX did not reach the level of statistical significance .
Finding showed that EGCG intake moderately accelerates EE and reduces RQ .
The analyses revealed that the EGCG result ed in difference in RQ and EE but the effect on the other measures of energy metabolism was relatively mild .
Possibly , EGCG alone has the potential to increase metabolic rate at 300 mg dose .
Collectively , the outcome supports the findings that EGCG has an effect on metabolic parameters .
Green tea catechins ( GTCs ) are known to improve fat oxidation ( FOX ) during fasted , rested and exercise conditions wherein epigallocatechin-3-gallate ( EGCG ) is thought to be the most pharmacologically active and has been studied extensively .
From the available data of r and omized controlled trials ( RCTs ) on EGCG , we carried out a systematic review and meta- analysis to eluci date whether EGCG consumption indeed increase energy expenditure ( EE ) and promote FOX .