The effect of antioxidant vitamin supplementation on traditional cardiovascular risk factors

Background Evidence from observational epidemiologic studies has indicated that antioxidants consumed through the diet or as dietary supplements lower the risk of developing atherosclerotic cardiovascular disease. Evidence suggesting that the major mechanism for the protective effect of antioxidants is mediated through decreased oxidation of lipids, particularly low-density lipoprotein (LDL) cholesterol is accumulating. Other evidence, however, suggests that antioxidants may influence traditional modifiable cardiovascular risk factors such as the blood pressure and serum lipids favorably. The purpose of this study was to determine the effect of antioxidant vitamin supplementation on modifiable risk factors for atherosclerotic cardiovascular disease. Design A randomized, placebo-controlled, clinical trial of antioxidant vitamin supplementation, conducted at a single community-based clinical research center. Methods We assigned 297 retired teachers who were members of the Maryland Retired Teachers Association randomly to 2-4 months of dietary supplementation with placebo or combined antioxidant vitamin capsules providing 400 IU/day vitamin E, 500 mg/day vitamin C, and 6 mg/day β-carotene. The outcome measures were the blood pressure, fasting serum total cholesterol, high-density lipoprotein cholesterol, LDL cholesterol, and fasting glucose. Results After 2-4 months of supplementation the combined antioxidant supplement had had no significant effect on the systolic and diastolic blood pressures, fasting serum lipids (total cholesterol, high-density lipoprotein cholesterol, and LDL cholesterol) and fasting glucose, with unadjusted and adjusted analyses. Conclusion Data from this trial suggest that the protective effect from antioxidant vitamin supplementation, if there is one, likely results from mechanisms other than modification of traditionally modifiable cardiovascular risk factors.