CITRUS-FRUIT SUPPLEMENTATION REDUCES LIPOPROTEIN OXIDATION IN YOUNG MEN INGESTING A DIET HIGH IN SATURATED FAT - PRESUMPTIVE EVIDENCE FOR AN INTERACTION BETWEEN VITAMIN-C AND VITAMIN-E IN-VIVO

To determine the effects of vitamin C on cardiovascular risk factors, we studied dietary vitamin C enrichment in 36 healthy male students co nsuming a diet high in saturated fatty acids. After a I-mo run-in peri od during which the subjects consumed approximate to 50 mg ascorbic ac id/d (low-C diet), half of the subjects were randomly assigned to rece ive 500 mg ascorbic acid/d for an additional 2 mo (high-C diet). Plasm a ascorbic acid increased from 13.5 mu mol/L with the low-C diet to 51 .7 mu mol/L with the high-C diet. Plasma cholesterol increased slightl y with the high-C diet, but not above baseline concentrations. This in crease was offset by an increase in the lag period of in vitro LDL oxi dation, which correlated with plasma ascorbic acid concentrations (r = 0.735, P = 0.0012). Lipoprotein vitamin E concentrations were unchang ed with the two diets. There were no effects on concentrations of fibr inogen or factor VII. The fact that ascorbic acid reduced the in vitro susceptibility of lipoproteins to oxidation provides presumptive evid ence for an interaction between aqueous and lipophilic antioxidants (v itamins C and E) in maintaining the integrity of LDL particles.