Effect of folic acid and antioxidant vitamins on endothelial dysfunction in patients with coronary artery disease

OBJECTIVES: The purpose of this study was to determine whether lowering homocysteine levels with folic acid, with or without antioxidants, will improve endothelial dysfunction in patients with coronary artery disease (CAD). BACKGROUND: Elevated plasma homocysteine levels are a risk factor for atherosclerosis. Homocysteine may promote atherogenesis through endothelial dysfunction and oxidative stress. METHODS: In a double-blind, placebo-controlled, randomized trial, we used vascular ultrasound to assess the effect of folic acid alone or with antioxidants on brachial artery endothelium-dependent flow-mediated dilation (FMD). Seventy-five patients with CAD (screening homocysteine level ≥ 9 μmol/liter) were randomized equally to one of three groups: placebo, folic acid alone or folic acid plus antioxidant vitamins C and E. Patients were treated for four months. Plasma folate, homocysteine, FMD and nitroglycerin-mediated dilation were measured before and after four months of treatment. RESULTS: Plasma folate, homocysteine and FMD were unchanged in the placebo group. Compared with placebo, folic acid alone increased plasma folate by 475% (p < 0.001), reduced plasma homocysteine by 11% (p = 0.23) and significantly improved FMD from 3.2 ± 3.6% to 5.2 ± 3.9% (p = 0.04). The improvement in FMD correlated with the reduction in homocysteine (r = 0.5, p = 0.01). Folic acid plus antioxidants increased plasma folate by 438% (p < 0.001), reduced plasma homocysteine by 9% (p = 0.56) and insignificantly improved FMD from 2.6 ± 2.4% to 4.0 ± 3.7% (p = 0.45), as compared with placebo. Nitroglycerin-mediated dilation did not change significantly in any group. CONCLUSIONS: Folic acid supplementation significantly improved endothelial dysfunction in patients with coronary atherosclerosis. Further clinical trials are required to determine whether folic acid supplementation may reduce cardiovascular events. (C) 2000 by the American College of Cardiology.