BETA-CAROTENE ENHANCES THE RECOVERY OF LYMPHOCYTES FROM OXIDATIVE DNA-DAMAGE

Epidemiological studies have revealed a strong correlation between hig h intake of fruit and vegetables and low incidence of certain cancers. Micronutrients present in these foods are thought to decrease free ra dical attack on DNA and hence protect against mutations that cause can cer, but the fine details of the causal mechanism have still to be elu cidated. Whether dietary factors can modulate DNA repair -- a crucial element in the avoidance of carcinogenesis -- is an intriguing questio n that has not yet been satisfactorily answered. In order to investiga te the effects of beta-carotene on oxidative damage and its repair, vo lunteers were given a single 45 mg dose and lymphocytes taken before a nd after the supplement were treated in vitro with H2O2. DNA strand br eaks and oxidised pyrimidines were measured at intervals, to monitor t he removal of oxidative DNA damage. We found inter-individual variatio ns in response. In cases where the baseline plasma beta-carotene conce ntration was high, or where supplementation increased the plasma conce ntration, recovery from oxidative damage (i.e. removal of both oxidise d pyrimidines and strand breaks) was relatively rapid. However, what s eems to be an enhancement of repair might in fact represent an amelior ation of the continuing oxidative stress encountered by the lymphocyte s under in vitro culture conditions. We found that culture in a 5% oxy gen atmosphere enhanced recovery of lymphocytes from H2O2 damage.