EFFECT OF VITAMIN-C ON PLASMA-LIPIDS

OBJECTIVE: To review the effects of vitamin C (ascorbic acid) on plasm a lipid concentrations, and to address the proposed mechanisms through which vitamin C may potentially alter lipid concentrations. DATA SOUR CE: A MEDLINE search was performed to identify pertinent English-langu age literature including studies, abstracts, and review articles. Key search terms were vitamin C, ascorbic acid, lipoproteins, lipids, and atherosclerosis. STUDY SELECTION AND DATA EXTRACTION: Studies examinin g the relationships between vitamin C and plasma lipid concentrations including animal, observational, and clinical trials were selected. Be cause there were no large randomized, controlled clinical trials, data were extracted from all clinical trials, regardless of design. Review articles discussing the effects of vitamin C on plasma lipid concentr ations and the atherosclerotic process also were included. Pertinent i nformation, as judged by the authors, was extracted for discussion. DA TA SYNTHESIS: Evidence suggests an inverse relationship between vitami n C intake and the development of atherosclerosis, although the effect has not yet been proven in clinical trials. It has been postulated th at this effect might be mediated not only through the antioxidant prop erties of vitamin C, but also through a plasma lipid-modifying effect. Data from animal and observational trials suggest that high vitamin C concentrations may correlate negatively with concentrations of total cholesterol, triglycerides, and low-density lipoproteins and positivel y with high-density lipoproteins. Other studies, however, have not con firmed these findings. Similarly, results from clinical trials have be en widely variable and inconclusive. CONCLUSIONS: Analysis of the lite rature suggests an association between vitamin C and plasma lipid conc entrations and a potential role in slowing the development of atherosc lerosis. Significant variations and inadequacies in trial design, howe ver, prohibit definitive conclusions. On the basis of these preliminar y data, it appears that there is justification for additional well-des igned trials to further evaluate the relationship between vitamin C an d plasma lipid concentrations.