Green tea extract reduces blood pressure, inflammatory biomarkers, and oxidative stress and improves parameters associated with insulin resistance in obese, hypertensive patients. Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics? A randomized, double-blind, and placebo-controlled clinical trial. Effects of Green Tea Extract on Insulin Resistance and Glucagon-Like Peptide 1 in Patients with Type 2 Diabetes and Lipid Abnormalities: A Randomized, Double-Blinded, and Placebo-Controlled Trial Phase I study of green tea extract in patients with advanced lung cancer The Effect of Ginkgo biloba and Camellia sinensis Extracts on Psychological State and Glycemic Control in Patients with Type 2 Diabetes Mellitus Green Tea Extract and Catechol-O-Methyltransferase Genotype Modify Fasting Serum Insulin and Plasma Adiponectin Concentrations in a Randomized Controlled Trial of Overweight and Obese Postmenopausal Women. The safety of green tea extract supplementation in postmenopausal women at risk for breast cancer: results of the Minnesota Green Tea Trial. 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. A Randomized Controlled Trial of Green Tea Extract Supplementation and Mammographic Density in Postmenopausal Women at Increased Risk of Breast Cancer The Effect of Green Tea and Sour Tea on Blood Pressure of Patients with Type 2 Diabetes: A Randomized Clinical Trial Does supplementation with green tea extract improve acne in post-adolescent women? A randomized, double-blind, and placebo-controlled clinical trial. The effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus: double-blind randomized study. Supplementation with Brazil nuts and green tea extract regulates targeted biomarkers related to colorectal cancer risk in humans. Acute ingestion of catechin-rich green tea improves postprandial glucose status and increases serum thioredoxin concentrations in postmenopausal women. Randomized controlled trial for an effect of green tea consumption on insulin resistance and inflammation markers. No effects of three-week consumption of a green tea extract on time trial performance in endurance-trained men. Role of (−)-epigallocatechin gallate in the pharmacokinetic interaction between nadolol and green tea in healthy volunteers Does green tea affect postprandial glucose, insulin and satiety in healthy subjects: a randomized controlled trial Phase II Randomized, Placebo-Controlled Trial of Green Tea Extract in Patients with High-Risk Oral Premalignant Lesions Phase I trial of oral green tea extract in adult patients with solid tumors. The effect of green tea extract supplementation on exercise-induced oxidative stress parameters in male sprinters Effect of green tea extract on obese women: a randomized, double-blind, placebo-controlled clinical trial. Nonpharmacological interventions to prevent type 2 diabetes in women diagnosed with gestational diabetes mellitus: a systematic overview
Green tea ( GT ) consumption is known to be associated with enhanced cardiovascular and metabolic health . The purpose of this study is to examine the hypothesis that supplementation with GT alters insulin resistance and associated cardiovascular risk factors in obese , hypertensive patients . In a double-blind , placebo-controlled trial , 56 obese , hypertensive subjects were r and omized to receive a daily supplement of 1 capsule that contained either 379 mg of GT extract ( GTE ) or a matching placebo , for 3 months . At baseline and after 3 months of treatment , the anthropometric parameters , blood pressure , plasma lipid levels , glucose levels , creatinine levels , tumor necrosis factor α levels , C-reactive protein levels , total antioxidant status , and insulin levels were assessed . Insulin resistance was evaluated according to the homeostasis model assessment -insulin resistance protocol . After 3 months of supplementation , both systolic and diastolic blood pressures had significantly decreased in the GTE group as compared with the placebo group ( P < .01 ) . Considerable ( P < .01 ) reductions in fasting serum glucose and insulin levels and insulin resistance were observed in the GTE group when compared with the placebo group . Serum tumor necrosis factor α and C-reactive protein were significantly lower , whereas total antioxidant status increased in the GTE group compared with the placebo ( P < .05 ) . Supplementation also contributed to significant ( P < .05 ) decreases in the total and low-density lipoprotein cholesterol and triglycerides , but an increase in high-density lipoprotein cholesterol . In conclusion , daily supplementation with 379 mg of GTE favorably influences blood pressure , insulin resistance , inflammation and oxidative stress , and lipid profile in patients with obesity-related hypertension 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 The aim of this study is to investigate the effect of green tea extract on patients with type 2 diabetes mellitus and lipid abnormalities on glycemic and lipid profiles , and hormone peptides by a double-blinded , r and omized and placebo-controlled clinical trial . This trial enrolled 92 subjects with type 2 diabetes mellitus and lipid abnormalities r and omized into 2 arms , each arm comprising 46 participants . Of the participants , 39 in therapeutic arm took 500 mg green tea extract , three times a day , while 38 in control arm took cellulose with the same dose and frequency to complete the 16-week study . Anthropometrics measurements , glycemic and lipid profiles , safety parameters , and obesity-related hormone peptides were analyzed at screening and after 16-week course . Within-group comparisons showed that green tea extract caused a significant decrease in triglyceride and homeostasis model assessment of insulin resistance index after 16 weeks . Green tea extract also increased significantly high density lipoprotein cholesterol . The HOMA-IR index decreased from 5.4±3.9 to 3.5±2.0 in therapeutic arm only . Adiponectin , apolipoprotein A1 , and apolipoprotein B100 increased significantly in both arms , but only glucagon-like peptide 1 increased in the therapeutic arm . However , only decreasing trend in triglyceride was found in between-group comparison . Our study suggested that green tea extract significantly improved insulin resistance and increased glucagon-like peptide 1 only in within-group comparison . The potential effects of green tea extract on insulin resistance and glucagon-like peptide 1 warrant further investigation . Trial Registration Clinical Trials.gov Purpose Epidemiologic studies suggest that consumption of green tea may have a protective effect against the development of several cancers . Pre clinical studies of green tea and its polyphenolic components have demonstrated antimutagenic and anticarcinogenic activity , and inhibition of growth of tumor cell lines and animal tumor models , including lung cancer . Green tea may also have chemopreventive properties , and enhancement of cytotoxicity of chemotherapeutic agents has been demonstrated . This trial was design ed to determine the maximum tolerated dose ( MTD ) of green tea extract ( GTE ) in patients with advanced lung cancer . Methods A total of 17 patients with advanced lung cancer were registered to receive once-daily oral dosing of GTE at a starting dose of 0.5 g/m2 per day , with an accelerated dose-escalation scheme . Results On this schedule , the MTD of GTE was 3 g/m2 per day , and at this dose ,  GTE  was well tolerated with no grade 3 or 4 toxicity seen . Dose-limiting toxicities were diarrhea , nausea and hypertension . No objective responses were seen in this trial . Seven patients had stable disease ranging from 4 to 16 weeks ; no patient remained on therapy longer than 16 weeks due to the development of progressive disease . Conclusions This study suggests that while relatively nontoxic at a dose of 3 g/m2 per day , GTE likely has limited activity as a cytotoxic agent , and further study of GTE as a single-agent in established malignancies may not be warranted . Further studies should focus on the potential chemopreventive and chemotherapy-enhancing properties of GTE Interest in finding natural antioxidants for use in food or medical material s to prevent free radical imbalance has increased considerably over the past years . The aim of this research was to evaluate changes in glycemic control and psychological state of patients with type 2 diabetes mellitus ( T2DM ) after use of antioxidant plant preparations .  Fifty-six patients with T2DM were r and omly allocated to receive st and ardized Ginkgo biloba L. leaves dry extract , green tea dry extract , or placebo capsules .  Diabetes glycemic control measured as glycated hemoglobin ( HbA1c ) level , antioxidant state and psychological data were evaluated at baseline , after 9 and 18 months of using either antioxidant preparations or placebo . The level of perceived stress lowered significantly after 9 months ( p=0.038 ) and 18 months ( p=0.030 ) , and the psychological aspect of quality of life significantly improved after 18 months ( p=0.019 ) of use of G. biloba extract . No significant differences were detected after using green tea extract . In patients using placebo , significant lowering of HbA1c level was observed after 18 months ( p=0.017 ) . In conclusion , antioxidant G. biloba leaf extract exhibited a mild effect on psychological state and a trend of improving glycemic control in patients with type 2 diabetes mellitus BACKGROUND Green tea consumption has been associated with favorable changes in body weight and obesity-related hormones , although it is not known whether these changes result from green tea polyphenols or caffeine . OBJECTIVE We examined the impact of decaffeinated green tea extract ( GTE ) containing 843 mg of (-)-epigallocatechin-3-gallate on anthropometric variables , obesity-associated hormones , and glucose homeostasis . METHODS The Minnesota Green Tea Trial was a 12-mo r and omized , double-blind , placebo-controlled clinical trial of 937 healthy postmenopausal women assigned to either decaffeinated GTE ( 1315 mg total catechins/d ) or a placebo  , stratified by catechol-O-methyltransferase ( COMT ) genotype . This study was conducted in a subset of 237 overweight and obese participants [ body mass index ( BMI ) ≥25 kg/m(2 ) ] . RESULTS No changes in energy intake , body weight , BMI , or waist circumference ( WC ) were observed over 12 mo in women taking GTE ( n = 117 ) or placebo ( n = 120 ) . No differences were seen in circulating leptin , ghrelin , adiponectin , or glucose concentrations at month 12 . Participants r and omly assigned to GTE with baseline insulin ≥10 μIU/mL ( n = 23 ) had a decrease in fasting serum insulin from baseline to month 12 ( -1.43 ± 0.59 μIU/mL ) , whereas those r and omly assigned to placebo with baseline insulin ≥10 μIU/mL ( n = 19 ) had an increase in insulin over 12 mo ( 0.55 ± 0.64 μIU/mL , P < 0.01 ) . Participants with the homozygous high-activity ( G/G ) form of COMT had significantly lower adiponectin ( 5.97 ± 0.50 compared with 7.58 ± 0.53 μg/mL , P = 0.03 ) and greater insulin concentrations ( 7.63 ± 0.53 compared with 6.18 ± 0.36 μIU/mL , P = 0.02 ) at month 12 compared with those with the low-activity ( A/A ) genotype , regardless of treatment group . CONCLUSIONS Decaffeinated GTE was not associated with reductions in body weight , BMI , or WC and did not alter energy intake or mean hormone concentrations in healthy postmenopausal women over 12 mo . GTE decreased fasting insulin concentrations in those with elevated baseline fasting concentrations . The high-activity form of the COMT enzyme may be associated with elevations in insulin and a reduction in adiponectin concentrations over time . This trial was registered at http://www . clinical trials.gov as NCT00917735 Green tea is thought to provide health benefits , though adverse reactions to green tea extract ( GTE ) have been reported . We conducted a r and omized , double-blind , placebo-controlled study of GTE on breast cancer biomarkers , including mammographic density , in which 1075 postmenopausal women were r and omly 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 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 r and omized , 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 sub study was conducted in 121 overweight/obese participants [ body mass index ( BMI ) ( kg/m(2 ) ) ≥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/cm(2 ) ; 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 . clinical trials.gov as NCT00917735 Epidemiologic and animal studies suggest a protective role of green tea against breast cancer . However , the underlying mechanism is not understood . We conducted a r and omized , double-blinded , placebo-controlled phase II clinical trial to investigate whether supplementation with green tea extract ( GTE ) modifies mammographic density ( MD ) , as a potential mechanism , involving 1,075 healthy postmenopausal women . Women assigned to the treatment arm consumed daily 4 decaffeinated GTE capsules containing 1,315 mg total catechins , including 843 mg epigallocatechin-3-gallate ( EGCG ) for 12 months . A computer-assisted method ( Madena ) was used to assess MD in digital mammograms at baseline and month 12 time points in 932 completers ( 462 in GTE and 470 in placebo ) . GTE supplementation for 12 months did not significantly change percent MD ( PMD ) or absolute MD in all women . In younger women ( 50–55 years ) , GTE supplementation significantly reduced PMD by 4.40 % as compared with the placebo with a 1.02 % PMD increase from pre- to postintervention ( P = 0.05 ) , but had no effect in older women ( Pinteraction = 0.07 ) . GTE supplementation did not induce MD change in other subgroups of women stratified by catechol-O-methyltransferase genotype or level of body mass index . In conclusion , 1-year supplementation with a high dose of EGCG did not have a significant effect on MD measures in all women , but reduced PMD in younger women , an age-dependent effect similar to those of tamoxifen . Further investigation of the potential chemopreventive effect of green tea intake on breast cancer risk in younger women is warranted . Cancer Prev Res ; 10(12 ) ; 710–8 . © 2017 AACR ABSTRACT Introduction : The use of herbal medicines including different types of tea is among the different strategies for preventing and controlling the side-effects of diabetes . The aim of the present study was to compare the effect of sour tea and green tea on mildly hypertensive patients with diabetes . Methods : The present study was a r and omized clinical trial in which 100 mildly hypertensive patients with diabetes were r and omly assigned into sour tea group ( ST ) and green tea group ( GT ) . They were instructed to drink sour tea and green tea infusion , respectively , three times a day 2 hr after each meal for 4 weeks . The participants ’ blood pressure was measured at days 1 , 15 , and at the end of study . Results : The systolic pressure of both groups statistically decreased at the end of the study ; it decreased from 123.1 ± 15.5 to 116.8 ± 16.3 mmHg in the ST and from 119.4 ± 15.1 to 114.8 ± 15.9 mmHg in the GT . The diastolic pressure of both groups statistically decreased by the end of the study ; it decreased from 79.4 ± 11.1 to 74.5 ± 9.3 mmHg in the ST and from 78.9 ± 8.3 to 75.3 ± 7.7 mmHg in the GT . The therapeutic effectiveness of tea drinking by the end of intervention was 43.5 % in the ST and 39.6 % in the GT compared to the beginning . Conclusions : The present study revealed that mildly hypertensive type 2 diabetic individuals who drink three glasses of green or sour tea daily for 4 weeks show significant decreased systolic and diastolic blood pressures BACKGROUND Green tea is believed to have beneficial effects in the prevention and treatment of acne . OBJECTIVE To examine the effects of a decaffeinated green tea extract ( GTE ) , providing a daily dose of 856 mg of epigallocatechin gallate ( EGCG ) upon women with post-adolescent acne . METHODS A r and omized , double-blind , placebo-controlled clinical trial was conducted from May 2012 through October 2013 . A final group of 80 subjects were r and omly assigned to receive either 1500 mg of decaffeinated GTE or placebo ( cellulose ) daily for 4 weeks . Inflammatory lesion counts were used as the major outcome measurement . At baseline and after 4 weeks of treatment , anthropometric measurements , fasting glucose levels and a lipid profile were measured from both groups . RESULTS Sixty-four of 80 women , from 25 to 45 years of age with moderate-to-severe acne completed the study . Statistically significant differences were noted in inflammatory lesion counts distributed on the nose , periorally and on the chin between the two groups . However , there were no significant differences between groups for total lesion counts . Within-group comparison revealed that the GTE group had significant reductions in inflammatory lesions distributed on the forehead and cheek , and significant reductions in total lesion counts . GTE result ed in significant reductions in total cholesterol levels within the GTE group . CONCLUSIONS GTE result ed in significant reductions in lesions located on the nose , perioral area and chin . More research is required to determine whether a decaffeinated GTE st and ardized for EGCG content will provide clinical benefits in women with post-adolescent acne Recent evidence suggests that tea from Camellia sinensis ( eg , green , oolong , and black tea ) may have a hypoglycemic effect . We evaluated the ability of an extract of green and black tea to improve glucose control over a 3-month period . A double-blind , placebo-controlled , r and omized multiple-dose ( 0 , 375 , or 750 mg per day for 3 months ) study in adults with type 2 diabetes mellitus not taking insulin was performed . The primary end point was change in glycosylated hemoglobin at 3 months . The 49 subjects who completed this study were predominantly white with an average age of 65 years and a median duration of diabetes of 6 years , and 80 % of them reported using hypoglycemic medication .  After 3 months , the mean changes in glycosylated hemoglobin were + 0.4 ( 95 % confidence interval , 0.2 - 0.6 ) , + 0.3 ( 0.1 - 0.5 ) , and + 0.5 ( 0.1 - 0.9 ) in the placebo , 375-mg , and 750-mg arms , respectively . The changes were not significantly different between study arms . We did not find a hypoglycemic effect of extract of green and black tea in adults with type 2 diabetes mellitus Se and green tea have been shown in epidemiological , observational and pre clinical studies to be inversely related to the risk of developing colorectal cancer ( CRC ) . However , there are limited studies to evaluate their regulatory effects on genes/proteins that relate to CRC oncogenesis in human subjects , such as selenoproteins , WNT signalling pathway , inflammation and methylation . This study examined the effects of supplementation of Se using Brazil nuts and green tea extract ( GTE ) capsules , alone and in combination , on targeted biomarkers . In total , thirty-two volunteers ( > 50 years of age ) with plasma Se≤1·36 µmol/l were r and omised to one of three treatment groups : nine to Se ( approximately 48 µg/d ) as six Brazil nuts , eleven to four GTE capsules ( 800 mg (-)-epigallocatechin-3-gallate ) and twelve to a combination of Brazil nuts and GTE . Blood and rectal biopsies were obtained before and after each intervention . Plasma Se levels , rectal selenoprotein P ( SePP ) and β-catenin mRNA increased significantly in subjects consuming Brazil nuts alone or in combination , whereas rectal DNA methyltransferase ( DNMT1 ) and NF-κB mRNA were reduced significantly in subjects consuming GTE alone or in combination . None of the interventions significantly affected rectal acetylated histone H3 or Ki-67 expression at the protein level or plasma C-reactive protein . Effects of the combination of Brazil nuts and GTE did not differ from what would be expected from either agent alone . In conclusion , supplementation of Brazil nuts and /or GTE regulates targeted biomarkers related to CRC oncogenesis , specifically genes associated with selenoproteins ( SePP ) , WNT signalling ( β-catenin ) , inflammation ( NF-κB ) and methylation ( DNMT1 ) . Their combination does not appear to provide additional effects compared with either agent alone 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 To study the effects of the intake of green tea and polyphenols , which are a component of green tea , on insulin resistance and systemic inflammation , a r and omized controlled trial was conducted on 66 patients aged 32 - 73 y ( 53 males and 13 females ) with borderline diabetes or diabetes . Subjects in the intervention group were asked to take a packet of green tea extracts/powder containing 544 mg polyphenols ( 456 mg catechins ) daily , which was a dose that could be taken without difficulty , and were asked to divide the green tea extracts/powder in a packet into 3 or 4 fractions dissolved in hot water everyday and to take a fraction after every meal or snack for 2 mo , in addition to daily food intake . The subjects in the control group were simply followed . To calculate the level of green tea polyphenol intake that the subject usually drank at home , the subject was asked to taste 3 teas of different strengths ( 1 , 2 and 3 % ) and the tea that was closest to the one that the subject drank at home , was selected by each subject . After 2 mo , the mean daily polyphenol intake in the intervention group was 747 mg , which was significantly higher than that of 469 mg in the control group . In the intervention group , the body weight , BMI , systolic and diastolic blood pressures , blood glucose level , Hb A1c level , insulin level and HOMA index after taking the supplementation for 2 mo , were lower than the respective value before intervention : however , these parameters in the intervention group at 2 mo did not significantly differ from those in the control group . Within the intervention group , changes in insulin level tended to be associated with changes in polyphenol intake . In addition , changes in BMI were associated with changes in blood glucose level and insulin level . In conclusion , the daily supplementary intake of 500 mg green tea polyphenols did not have clear effects on blood glucose level , Hb A1c level , insulin resistance or inflammation markers . The positive correlation between the level of polyphenol intake and insulin level warrants further studies on the effect of green tea on insulin resistance The purpose of this study was to examine the effects of three-week consumption of green tea extract ( GTE ) supplementation on time trial performance and metabolism during cycling in endurance athletes . Nine endurance-trained men participated in this double-blind and placebo-controlled cross-over study . At the end of the supplementation period with GTE ( 159 mg/day total catechins ) or placebo , respectively , subjects cycled at 50 % of the individual maximal power output for 2 hours , followed by a 30-minute time trial . Respiratory gas exchange , fatty acids , 3-beta-hydroxybutyrate , lactate , glucose , interleukin-6 , thiobarbituric acid reactive substances , creatine kinase , and C-reactive protein ( CRP ) were measured 1 hour before , during , and 1 hour after the exercise test . Blood lipids were measured at rest before cycling . There was no significant effect on performance , energy metabolism , or any other measured parameter , except for CRP , which was significantly reduced ( p = 0.045 ) after GTE supplementation compared to placebo . GTE supplementation did not affect time trial performance and energy metabolism in endurance-trained men in the non-fasting state . Further studies with athletes , particularly in the fed state , but with higher GTE doses , are needed to address the question whether green tea may influence energy metabolism and performance in athletes 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 Background Results of epidemiological studies have suggested that consumption of green tea could lower the risk of type 2 diabetes .  Intervention studies show that green tea may decrease blood glucose levels , and also increase satiety . This study was conducted to examine the postpr and ial effects of green tea on glucose levels , glycemic index , insulin levels and satiety in healthy individuals after the consumption of a meal including green tea . Methods The study was conducted on 14 healthy volunteers , with a crossover design . Participants were r and omized to either 300 ml of green tea or water . This was consumed together with a breakfast consisting of white bread and sliced turkey . Blood sample s were drawn at 0 , 15 , 30 , 45 , 60 , 90 , and 120 minutes . Participants completed several different satiety score scales at the same times . Results Plasma glucose levels were higher 120 min after ingestion of the meal with green tea than after the ingestion of the meal with water . No significant differences were found in serum insulin levels , or the area under the curve for glucose or insulin . Subjects reported significantly higher satiety , having a less strong desire to eat their favorite food and finding it less pleasant to eat another mouthful of the same food after drinking green tea compared to water . Conclusions Green tea showed no glucose or insulin-lowering effect . However , increased satiety and fullness were reported by the participants after the consumption of green tea . Trial registration Epidemiologic and pre clinical data support the oral cancer prevention potential of green tea extract ( GTE ) . We r and omly assigned patients with high-risk oral premalignant lesions ( OPL ) to receive GTE at 500 , 750 , or 1,000 mg/m2 or placebo thrice daily for 12 weeks , evaluating biomarkers in baseline and 12-week biopsies . The OPL clinical response rate was higher in all GTE arms ( n = 28 ; 50 % ) versus placebo ( n = 11 ; 18.2 % ; P = 0.09 ) but did not reach statistical significance . However , the two higher-dose GTE arms [ 58.8 % ( 750 and 1,000 mg/m2 ) , 36.4 % ( 500 mg/m2 ) , and 18.2 % ( placebo ) ; P = 0.03 ] had higher responses , suggesting a dose-response effect . GTE treatment also improved histology ( 21.4 % versus 9.1 % ; P = 0.65 ) , although not statistically significant . GTE was well tolerated , although higher doses increased insomnia/nervousness but produced no grade 4 toxicity . Higher mean baseline stromal vascular endothelial growth factor ( VEGF ) correlated with a clinical ( P = 0.04 ) but not histologic response . Baseline scores of other biomarkers ( epithelial VEGF , p53 , Ki-67 , cyclin D1 , and p16 promoter methylation ) were not associated with a response or survival . Baseline p16 promoter methylation ( n = 5 ) was associated with a shorter cancer-free survival . Stromal VEGF and cyclin D1 expression were downregulated in clinical ly responsive GTE patients and upregulated in nonresponsive patients at 12 weeks ( versus at baseline ) . An extended ( median , 27.5 months ) follow-up showed a median time to oral cancer of 46.4 months . GTE may suppress OPLs , in part through reducing angiogenic stimulus ( stromal VEGF ) . Higher doses of GTE may improve short-term ( 12-week ) OPL outcome . The present results support longer-term clinical testing of GTE for oral cancer prevention PURPOSE This trial was design ed to determine the maximum-tolerated dose , toxicity , and pharmacology of oral green tea extract ( GTE ) once daily or three times daily . PATIENTS AND METHODS Cohorts of three or more adult cancer patients were administered oral GTE with water after meals one or three times daily for 4 weeks , to a maximum of 6 months , depending on disease response and patient tolerance . Pharmacokinetic analyses were encouraged but optional . RESULTS Dose levels of 0.5 to 5.05 g/m(2 ) qd and 1.0 to 2.2 g/m(2 ) tid were explored . A total of 49 patients were studied . PATIENT CHARACTERISTICS median age , 57 years ( range , 27 to 77 years ) ; 23 patients were women ( 47 % ) ; 98 % had a Zubrod PS of 1 % ; 98 % had PS of 1 ; and 21 had non-small-cell lung , 19 had head & neck cancer , three had mesothelioma , and six had other .  Mild to moderate toxicities were seen at most dose levels and promptly reversed on discontinuation of GTE .  Dose-limiting toxicities were caffeine related and included neurologic and gastrointestinal effects . The maximum-tolerated dose was 4.2 g/m(2 ) once daily or 1.0 g/m(2 ) three times daily . No major responses occurred ; 10 patients with stable disease completed 6 months of GTE . Pharmacokinetic analyses found accumulation of caffeine levels that were dose dependent , whereas epigallocatechin gallate levels did not accumulate nor appear dose related . CONCLUSION A dose of 1.0 g/m(2 ) tid ( equivalent to 7 to 8 Japanese cups [ 120 mL ] of green tea three times daily ) is recommended for future studies . The side effects of this preparation of GTE were caffeine related . Oral GTE at the doses studied can be taken safely for at least 6 months Background Although research suggests that antioxidant supplementation can protect against exercise-induced muscle damage and oxidative stress , also delayed post-exercise muscle recovery and hindered adaptation to training were reported in the supplemented athletes . Purpose The purpose of the study was to evaluate the effects of green tea extract ( GTE ) supplementation on selected blood markers of oxidative stress and muscle damage in sprinters during preparatory phase of their training cycle . Methods Sixteen sprinters participated in a double-blind , r and omized , placebo (PL)-controlled crossover study , including two 4-week treatment periods with PL and GTE ( 980 mg polyphenols daily ) . The sprinters performed two repeated cycle sprint tests ( RST ; 4 × 15 s , with 1-min rest intervals ) , after PL and GTE supplementation . Blood was sample d before ( at rest ) , 5 min after RST , and after the 24-h recovery . The activities of superoxide dismutase ( SOD ) and glutathione peroxidase were measured in erythrocytes , and total polyphenols , total antioxidant capacity ( TAC ) , uric acid ( UA ) , albumin ( AL ) , malondialdehyde ( MDA ) , and creatine kinase ( CK ) were determined in blood plasma . Results Repeated cycle sprint test performed after PL induced an increase in MDA , TAC , and SOD . Moreover , an increase in UA , AL , and CK was observed after RST irrespective of experimental conditions ( PL , GTE ) . Supplementation with GTE caused an increase in total polyphenols and TAC at rest , and a decrease in MDA and SOD after RST . No significant changes in sprint performance were noted after GTE , as compared to PL . Conclusions Supplementation with GTE prevents oxidative stress induced by RST in sprinters . Furthermore , GTE supplementation does not seem to hinder training adaptation in antioxidant enzyme system . On the other h and , neither prevention of exercise-induced muscle damage , nor an improvement in sprint performance is noted after GTE administration AIMS To examine the effect of green tea extract ( GTE ) on obese women and to explore the relationship between GTE and obesity-related hormone peptides . METHODS A r and omized , double-blind , placebo-controlled clinical trial was conducted from July 2006 to June 2007 in Taipei Hospital , Taiwan . Seventy-eight of 100 obese women aged between 16 and 60 years with BMI > 27 kg/m(2 ) and who had not received any other weight control maneuvers within the last 3 months completed this study . The subjects were r and omly divided into Groups A and B. Group A ( n=41 ) received GTE while Group B ( n=37 ) took cellulose as a placebo , one capsule ( 400 mg ) three times each day for 12 weeks . The body weight ( BW ) , body mass index ( BMI ) and waist circumflex ( WC ) were measured at the beginning of the study and after 12 weeks of treatment with GTE . The data were compared and expressed as % reduction . RESULTS There was only a 0.3 % reduction in BW ( 0.15 kg ) after 12 weeks of treatment with GTE . There was no statistical difference in % reduction in BW , BMI and WC between the GTE and placebo groups . Within group comparison revealed that the GTE group had significant reduction in LDL-cholesterol and triglyceride , and marked increase in the level of HDL-cholesterol , adiponectin and ghrelin . On the other h and , the placebo group showed significant reduction in triglyceride only , and a marked increase in the level of ghrelin alone . CONCLUSIONS This study showed no statistical difference in % reduction in BW , BMI and WC between the GTE and placebo groups after 12 weeks of treatment . The intake of GTE ( 491 mg catechins containing 302 mg EGCG ) for 12 weeks is considered safe as shown by the results This systematic overview summarizes the relevant evidence from multiple systematic review s of the benefits of nonpharmacological interventions for preventing  type 2 diabetes mellitus ( T2MD ) in women diagnosed with gestational diabetes mellitus ( GDM ) . A comprehensive search using the Cochrane Library , CINAHL , EMBASE and MEDLINE via Ovid SP , and PubMed data bases was completed on 18 November 2015 . Any systematic review s that evaluated r and omized controlled trials ( RCTs ) with defined nonpharmacological interventions for preventing T2DM in women diagnosed with GDM were eligible for inclusion . The authors independently performed critical appraisal s and quality assessment s of the included review s using the AMSTAR tool , and extracted data were converted to coherent values for tabular summarization . Six eligible review s of diet and /or exercise , breastfeeding , and reminder interventions were identified ; however , the method ologies of the review s varied greatly , and the majority of the evidence suggested unclear bias . We found inconsistent reporting on the rates at which diet and exercise interventions reduced the risk of T2DM progression , but these interventions were found to be effective at reducing glycemic load . Combined diet , exercise , and breastfeeding interventions proved to be effective at returning women to their postpartum weight . Neither diet alone nor exercise alone proved to be effective at lowering the risk of T2DM . Overall , there was no robust evidence to support the hypothesis that nonpharmacological interventions are effective at lowering the risk of T2DM in women diagnosed with GDM , and there was no consistent evidence showing that these interventions improved the predictor outcomes of T2DM , such as glycemic load or anthropometric changes
No evidence support the consumption of GT/GTE could reduce the levels of HbA1c , HOMA-IR , fasting insulin , or fasting glucose in people with pre-diabetes/T2DM .
Green tea or green tea extract ( GT/GTE ) has been demonstrated to reduce insulin resistance and improve glycemic control .
However , evidence for this health beneficial effect is inconsistent .
This systematic review evaluated the effect of GT/GTE on insulin resistance and glycemic control in people with pre-diabetes/type 2 diabetes mellitus ( T2DM ) .