Antioxidant vitamins and low-density-lipoprotein oxidation

Low-density-lipoprotein (LDL) oxidation was examined in 22 subjects (10 men, 12 women) after a daily dose of 18 mg [beta]-carotene, 900 mg vitamin C, and 200 mg [alpha]-tocopherol for 6 mo. Control subjects (12 men, 11 women) took no vitamin supplements. After 3-mo supplementation plasma concentrations of [beta]-carotene, [alpha]-tocopherol, and ascorbic acid increased fivefold (P < 0.001), 55% (P < 0.01), 27% (P < 0.05), respectively. There was no difference from baseline in rate of oxidation or total amount of conjugated diene produced between subjects taking or not taking vitamins. Malondialdehyde in LDL before and after oxidation was not different between the two groups. Lag time before the onset of oxidation was significantly lengthened after antioxidant supplementation (28% and 35% after 3 and 6 mo, respectively, P < 0.001). There was a significant independent correlation between percent change in lag time and percent change in plasma [alpha]-tocopherol (r = 0.47, P < 0.01).