The effects of beta-carotene and ascorbic acid on spontaneous and x-ray-induced appearance of micronuclei (MNs) in human lymphocytes were studied. For 12 d, three groups of healthy volunteers were given beta-carotene-deficient meals containing 100 mg ascorbic acid. There was no supplementation in the first 6 d but, in the last 6 d, the respective groups were given beta-carotene (30 mg), ascorbic acid (300 mg), or placebo. Blood samples were drawn on days 7 and 13 before breakfast, exposed either to x-ray irradiation or left unexposed and were cultured. Lymphocytes containing MNs were then counted. On day 7 the three groups showed comparable MN frequencies. On day 13 lymphocytes containing x-ray-induced MNs became less frequent in the beta-carotene but not the ascorbic acid group. Both before and after the supplementation, the MN frequency of irradiated lymphocytes showed a significant inverse correlation with plasma beta-carotene. These results strongly suggest that beta-carotene protects human lymphocytes from x-ray-induced genetic damage.

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