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 Diet supplementation with green tea extract epigallocatechin gallate prevents progression to glucose intolerance in db/db mice Randomized controlled trial for an effect of green tea consumption on insulin resistance and inflammation markers. 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 effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus: double-blind randomized study. Does green tea affect postprandial glucose, insulin and satiety in healthy subjects: a randomized controlled trial Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics? A randomized, double-blind, and placebo-controlled clinical trial. The impact of the catechol-O-methyltransferase genotype on the acute responsiveness of vascular reactivity to a green tea extract. Green tea extract reduces blood pressure, inflammatory biomarkers, and oxidative stress and improves parameters associated with insulin resistance in obese, hypertensive patients. The Effect of Ginkgo biloba and Camellia sinensis Extracts on Psychological State and Glycemic Control in Patients with Type 2 Diabetes Mellitus Long-term ingestion of a fermented soybean-derived Touchi-extract with alpha-glucosidase inhibitory activity is safe and effective in humans with borderline and mild type-2 diabetes. The Effect of Green Tea and Sour Tea on Blood Pressure of Patients with Type 2 Diabetes: A Randomized Clinical Trial Eicosapentaenoic acid improves insulin sensitivity and blood sugar in overweight type 2 diabetes mellitus patients: a double-blind randomised clinical trial. Herbal tea in the treatment of diabetes mellitus. Effects of Green Tea Supplementation on Elements, Total Antioxidants, Lipids, and Glucose Values in the Serum of Obese Patients Acute ingestion of catechin-rich green tea improves postprandial glucose status and increases serum thioredoxin concentrations in postmenopausal women. The Minnesota Green Tea Trial (MGTT), a randomized controlled trial of the efficacy of green tea extract on biomarkers of breast cancer risk: study rationale, design, methods, and participant characteristics
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 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 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 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 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 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 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 beneficial effects of green tea catechins , such as the proposed improvement in endothelial function , may be influenced by phase II metabolism during and after absorption . The methylation enzyme , catechol-O-methyltransferase ( COMT ) , has a missense mutation rs4680 ( G to A ) , proposed to result in a 40 % reduction in enzyme activity . In the present pilot study , twenty subjects ( ten of each homozygous COMT genotype ) were recruited .  Green tea extract capsules ( 836 mg green tea catechins ) were given in a fasted state , and a high-carbohydrate breakfast was given after 60 min . Blood sample s and vascular function measurements were taken at regular intervals . The change in digital volume pulse stiffness index ( SI ) from baseline was shown to be different between genotype groups at 120 and 240 min , with a lower SI in the GG individuals ( P ≤ 0·044 ) . The change in blood pressure from baseline also differed between genotype groups , with a greater increase in systolic ( P = 0·023 ) and diastolic ( P = 0·034 ) blood pressure at 120 min in the GG group . The GG [ corrected ] group was shown to have a greater increase in insulin concentrations at 120 min ( P = 0·019 ) and 180 min ( P = 0·008 ) compared with baseline , despite similar glucose profiles . No genotypic differences were found in vascular reactivity measured using laser Doppler iontophoresis , total nitrite , lipids , plasma total antioxidant capacity or inflammatory markers after ingestion of the green tea extract . In conclusion , SI and insulin response to the glucose load differed between the COMT genotype groups , and this may be suggestive of a green tea extract and genotype interaction 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 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 Water-extracted Touchi , a traditional Chinese food , exerts a strong inhibitory activity against rat intestinal alpha-glucosidase in foodstuffs , and Touchi-extract ( TE ) has been shown to have an antihyperglycemic effect in rats and humans after a single oral administration . In the present complementary study , the effects of powdered Houji-tea with or without ( placebo ) TE , a formula design ed to enhance good compliance , were monitored in a 3-mo double-blind r and omized group comparison study with placebo controls in humans with borderline and mild type-2 diabetes ( n = 36 ) . All subjects ingested Houji-tea with or without 0.3 g of TE before each of three meals per day for 3 mo . In the TE group , initial fasting blood glucose ( 6.9 + /- 0.1 mmol/L ) and glycated hemoglobin ( HbA(1c ) ; 6.1 + /- 0.1 % ) levels gradually decreased ; fasting blood glucose decreased significantly after 3 mo ( 6.4 + /- 0.3 mmol/L ; P < 0.05 ) as did HbA(1c ) ( 5.6 + /- 0.2 % ; P < 0.01 ) levels at 2 mo postingestion of TE and thereafter . In contrast , fasting blood glucose and HbA(1c ) levels did not change in the placebo group . In this study , other biochemical variables were not affected in any of the subjects , and no one complained of any side effects or abdominal distension . Moreover , there was no deterioration as assessed by fasting blood glucose and HbA(1c ) levels after withdrawal of TE ingestion . Thus , the alpha-glucosidase inhibitory TE demonstrated an antihyperglycemic effect and may prove useful for improving glycemic control in subjects suffering from borderline and type-2 diabetes mellitus 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 INTRODUCTION Diabetes mellitus is the most common metabolic disorder in humans , and its incidence is increasing rapidly worldwide . Although polyunsaturated fatty acids have beneficial effects on diabetes mellitus , previous data regarding the possible positive effects of n-3 fatty acids on glycaemic indices were inconclusive . We conducted a double-blind r and omised clinical trial to determine the effects of eicosapentaenoic acid ( EPA ) , an n-3 polyunsaturated fatty acid , on overweight patients with type 2 diabetes mellitus ( T2DM ) . METHODS This double-blind , placebo-controlled r and omised clinical trial was conducted on a total of 67 overweight patients with T2DM for a duration of three months . Of these 67 patients , 32 received 2 g purified EPA daily , while 35 received a placebo of 2 g corn oil daily . The patients ' fasting plasma glucose ( FPG ) , serum insulin , glycated haemoglobin ( HbA1c ) and insulin sensitivity indices were assessed . RESULTS After three months of EPA supplementation , the group that received EPA showed significant decreases in FPG ( p < 0.001 ) , HbA1c ( p = 0.01 ) and homeostasis model assessment of insulin resistance ( HOMA-IR ) ( p = 0.032 ) , when compared to the placebo group . EPA supplementation result ed in decreased serum insulin levels , with the levels between the EPA and placebo groups showing a significant difference ( p = 0.004 ) . CONCLUSION The results of our study indicate that EPA supplementation could improve insulin sensitivity . It was able to decrease serum insulin , FPG , HbA1c and HOMA-IR .  EPA could have beneficial effects on glycaemic indices in patients with T2DM OBJECTIVE To evaluate the effects of a native herbal tea in patients with type 2 diabetes . DESIGN R and omized , placebo-controlled , single-blind study . SETTING The Metabolic Centre at the University of Alberta Hospitals . SUBJECTS Forty volunteers with type 2 diabetes . INTERVENTIONS After a 1 month " run-in " period , subjects drank 250 mL/d of either the herbal tea or a placebo tea for 10 days , and were followed up for a further 4 weeks . OUTCOME MEASURES A responder analysis defined as a 10 % change in mean blood glucose levels based on 4 capillary glucose readings daily . Secondary end points included changes in HbA1c , fructosamine and response to a meal challenge using Ensure . RESULTS The responder analysis showed no benefit from the herbal tea .  Fructosamine levels before and after tea therapy decreased significantly in both study groups . Mean HbA1c levels and incremental areas under the glucose curve ( AUC ) in the meal challenge did not change in either study group . These data were reanalysed in hyperglycemic subjects with HbA1c levels greater than 120 % of normal . The responder analysis and HbA1c levels did not change in either group . Mean ( and st and ard deviation ) fructosamine levels , before and after tea therapy , were significantly lower in the herbal tea group than in the placebo tea group ( 361 [ 98 ] versus 338 [ 100 ] micromol/L , p < 0.01 compared with 338 [ 60 ] versus 323 [ 49 ] micromol/L , p = 0.08 ) . In the hyperglycemic subgroup the mean AUC during the meal challenge , before versus after tea therapy , was 776 ( 369 ) versus 639 ( 331 ) mmol/L ( p = 0.22 ) in the herbal tea group and 433 ( 125 ) versus 420 ( 173 ) mmol/L ( p = 0.90 ) in the placebo group . CONCLUSIONS Although the responder analysis failed to show an effect of the herbal tea , the data suggest there may be a short-term benefit from the tea in subjects with poor glycemic control The consumption of green tea has been associated with cardiovascular and metabolic diseases . There have been some studies on the influence of green tea on the mineral status of obese subjects , but they have not yielded conclusive results . The aim of the present study is to examine the effects of green tea extract on the mineral , body mass , lipid profile , glucose , and antioxidant status of obese patients . A r and omized , double-blind , placebo-controlled study was conducted . Forty-six obese patients were r and omly assigned to receive either 379 mg of green tea extract , or a placebo , daily for 3 months . At baseline , and after 3 months of treatment , the anthropometric parameters , blood pressure , and total antioxidant status were assessed , as were the levels of plasma lipids , glucose , calcium , magnesium , iron , zinc , and copper . We found that 3 months of green tea extract supplementation result ed in decreases in body mass index , waist circumference , and levels of total cholesterol , low-density cholesterol , and triglyceride . Increases in total antioxidant level and in zinc concentration in serum were also observed . Glucose and iron levels were lower in the green tea extract group than in the control , although HDL-cholesterol and magnesium were higher in the green tea extract group than in the placebo group . At baseline , a positive correlation was found between calcium and body mass index , as was a negative correlation between copper and triglycerides . After 3 months , a positive correlation between iron and body mass index and between magnesium and HDL-cholesterol , as well as a negative correlation between magnesium and glucose , were observed . The present findings demonstrate that green tea influences the body 's mineral status . Moreover , the results of this study confirm the beneficial effects of green tea extract supplementation on body mass index , lipid profile , and total antioxidant status in patients with obesity 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 Purpose The Minnesota Green Tea Trial ( MGTT ) was a r and omized , placebo-controlled , double-blinded trial investigating the effect of daily green tea extract consumption for 12 months on biomarkers of breast cancer risk . Methods Participants were healthy postmenopausal women at high risk of breast cancer due to dense breast tissue with differing catechol-O-methyltransferase ( COMT ) genotypes . The intervention was a green tea catechin extract containing 843.0 ± 44.0 mg/day epigallocatechin gallate or placebo capsules for 1 year . Annual digital screening mammograms were obtained at baseline and month 12 , and fasting blood and 24-h urine sample s were provided at baseline and at months 6 and 12 . Primary endpoints included changes in percent mammographic density , circulating endogenous sex hormones , and insulin-like growth factor axis proteins ; secondary endpoints were changes in urinary estrogens and estrogen metabolites and circulating F2-isoprostanes , a biomarker of oxidative stress . Results The MGTT screened more than 100,000 mammograms and r and omized 1,075 participants based on treatment  ( green tea extract vs. placebo ) , stratified by COMT genotype activity ( high COMT vs. low/intermediate COMT genotype activity ) . A total of 937 women successfully completed the study and 138 dropped out ( overall dropout rate = 12.8 % ) . Conclusions In this paper we report the rationale , design , recruitment , participant characteristics , and methods for biomarker and statistical analyses
The consumption of green tea did not decrease the levels of fasting plasma glucose , fasting serum insulin , OGTT-2 h glucose , haemoglobin A₁c and HOMA(IR ) in population s at risk of T2DM .
BACKGROUND Although the regular consumption of green tea or green tea extract has been considered to improve insulin sensitivity , the reported results are inconsistent .
Therefore , we conducted a meta- analysis to evaluate the effect of green tea or green tea extract on insulin sensitivity and glycaemic control in population s at risk of type 2 diabetes mellitus ( T2DM ) .