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 ) .
Genoprotective effects of green tea (Camellia sinensis) in human subjects: results of a controlled supplementation trial.
Green tea is rich in polyphenolic antioxidants and has widely reported but largely unsubstantiated health benefits . In the present study , genoprotective effects of two types of green tea were studied both in an in vitro and in a human supplementation trial . For the in vitro study , human lymphocytes were pre-incubated in tea ( 0·005 - 0·1 % , w/v ) , washed and subjected to oxidant challenge induced by H2O2 . In a placebo-controlled , cross-over supplementation study , eighteen healthy volunteers took 2 x 150 ml/d of 1 % ( w/v ) green tea ( ' Longjing ' green tea or ' screw-shaped ' green tea ) or water ( control ) for 4 weeks ( n 6 ) . Subjects took all the three treatments in a r and om order , with 6 weeks ' washout between each treatment . Fasting blood and urine were collected before and after each treatment . The comet assay was used to measure the resistance of lymphocytic DNA to H2O2-induced challenge . Basal oxidation-induced DNA damage was measured using the formamidopyrimidine glycosylase ( Fpg ) enzyme-assisted comet assay . Urine 7,8-dihydro-2-deoxyguanosine ( 8-oxodG , mol/mmol creatinine ) , a biomarker of whole-body oxidative stress , was measured by liquid chromatography with t and em MS . In vitro testing results of tea-treated cells showed increased ( P < 0·05 ) resistance of DNA to the challenge . In the supplementation trial , a significant ( P < 0·05 ) increase in resistance was also observed . Furthermore , the FPg comet data showed .20 % decrease in DNA damage  with tea supplementation : mean and st and ard deviation changes in % DNA in comet tail in the Fpg-assisted comet assay were : -5·96 ( SD 3·83 ) % after Longjing tea ; -6·22 ( SD 3·34 ) % after screw-shaped tea ; + 0·91 ( SD 5·79 ) % after water ( P < 0·05 ) . No significant changes in urine 8-oxodG were seen . The results indicate that green tea has significant genoprotective effects and provide evidence for green tea as a ' functional food '
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 ) .