Effect of a 4Month Tea Intervention on Oxidative DNA Damage among Heavy Smokers: Role of Glutathione S-Transferase Genotypes (original) (raw)

Reduced DNA repair capacity is believed to increase susceptibility to smoking-related cancers. Polymorphisms in several DNA repair genes have been reported but the role of these variants in generating DNA damage phenotypes in human populations has been less well studied. The aim of this study was to determine whether variation in DNA repair genes is related to smokers' increased susceptibility to DNA damage, and the impact of high tea drinking on this. We designed a phase II randomised controlled, 3-arm tea intervention trial to study the effect of high consumption (4 cups per day) of decaffeinated green or black tea or water on oxidative DNA damage, as measured by urinary 8-hydroxydeoxyguanosine (8-OHdG), among heavy smokers over a 4-month period and to evaluate the roles of XRCC1 genotypes as effect modifiers. A total of 120 heavy smokers were included in the analysis. Multiple linear regression models were used to estimate the main effects and interaction effect of green and black tea consumption on creatinine-adjusted urinary 8-OHdG, with or without adjustment for potential confounders. Finally, we studied whether the effect of treatment varied by XRCC1 status of the individual. In this randomised controlled trial among smokers, daily drinking of 4 cups of decaffeinated green tea was associated with statistically significant decrease in urinary excretion of 8-OHdG. We did find a greater effect of green tea consumption on urinary 8-OHdG levels among Arg399/Arg (p = 0.02) than among Arg399/Gln+Gln/Gln (p = 0.079) smokers. Decaffeinated black tea consumption had no effect on urinary 8-OHdG levels among heavy smokers. Our data show that consumption of 4 cups of tea per day is a feasible and safe approach and was associated with significant decrease in urinary 8-OHdG among green tea consumers after 4 months of use. Our results suggest that carriers of the polymorphic XRCC1 Gln399 allele may not significantly benefit from a green tea, and hence an antioxidant, intervention.