Serum carotenoids and oxidative DNA damage in human lymphocytes

Carotenoids are thought to act as antioxidants in vivo, decreasing oxidativ e damage to biomolecules and thus protecting against coronary heart disease and cancer. However, human intervention studies with p-carotene have given equivocal results in terms of cancer incidence. In an alternative molecula r epidemiological approach, we have employed the 'comet assay' (single cell alkaline gel electrophoresis) to measure strand breaks, oxidized pyrimidin es and altered purines in the DNA of lymphocytes from volunteers supplement ed with alp-carotene, lutein, lycopene or placebo. In addition, we measured concentrations of the main serum carotenoids, and vitamins E and C, by HPL C. We report a significant negative correlation between basal concentration s of total serum carotenoids and oxidized pyrimidines. A similar correlatio n was seen between individual carotenoids (notably lutein and p-carotene) a nd oxidized pyrimidines. However, carotenoid supplementation did not have a significant effect on endogenous oxidative damage. This suggests that ther e are some factors in the basal diet, probably found in fruit and vegetable s, that decrease oxidative damage to DNA, In this case, basal serum caroten oids may simply be markers of consumption of fruit and vegetables, they the mselves having little or no protective value.