Oxidative DNA damage, antioxidants and DNA repair: applications of the comet assay.

Estimates of background levels of oxidative base damage in human white blood cells vary enormously, from 300 down to 0.4 molecules of 8-oxoguanine per 10(6) guanines. An EC-funded Concerted Action, the European Standards Committee on Oxidative DNA Damage, is currently attempting to resolve the discrepancy and to agree a realistic estimate of basal endogenous oxidation. Oxidation of lymphocyte DNA is a useful marker of oxidative stress, and this can be decreased by supplementation with pure antioxidants or with foods rich in antioxidants. The steady-state level of DNA oxidation is ultimately controlled by the process of DNA repair; the extent to which this varies between individuals has yet to be established.