Green Tea Consumption Reduces Oxidative DNA Damage and Lipid Peroxidation in Smokers and Non‐Smokers

Abstract

Oxidative stress is associated with the pathogenesis of human diseases. Green tea reduces oxidative stress in animal models but effects in humans are equivocal. This study was conducted to examine the effects of green tea on biomarkers of oxidative stress and antioxidants in smokers and non‐smokers, using a placebo‐controlled, double‐blind crossover design. Fifteen non‐smokers and 12 smokers consumed 32 oz daily beverage of 2.75% green tea and placebo, each for 1 week, in random order. Blood and urine samples collected pre and post treatment were analyzed for 8‐hydroxydeoxyguanosine (8‐OHdG), malondialdehyde (MDA), glutathione (GSH), α‐tocopherol and ascorbic acid by HPLC. Differences between group means were examined by 3‐way ANOVA (α=0.05). Urinary and plasma MDA of smokers were significantly higher than non‐smokers (P=0.044, P=0.016). Urinary and lymphocyte 8‐OHdG were also higher in smokers, though not significantly (P=0.206, P=0.784). Urinary MDA, urinary and lymphocyte 8‐OHdG were reduced after green tea by 65.7%, 43.2% and 42.8%, respectively (P=0.0006, P=0.037, P=0.001). No changes were seen in plasma MDA, GSH, α‐tocopherol or ascorbic acid (P=0.931, P=0.611, P=0.323, P=0.963). Two groups of subjects (high versus low basal oxidative stress) were identified based on the median of each oxidative biomarker. Urinary MDA and lymphocyte 8‐OHdG in subjects with high basal oxidative stress were significantly reduced by 53.9% and 53.4% after green tea versus placebo (P=0.026, P=0.013); and urinary and plasma MDA were lowered by 47.2% and 13.7%, though not significantly (P=0.070, P=0.183). In conclusion, green tea consumption reduced oxidative DNA damage and lipid peroxidation in smokers and non‐smokers.Supported in part by internal IU funds.