RESUMO
OBJECTIVE: To study the influence of supplementation with antioxidants on factors, which might increase the risk of coronary heart disease (CHD) in Iranians. DESIGN: Twenty-one male volunteers enter the prospective, single-blind, randomized study. SETTING: The supplementation was conducted at the Cardiovascular Center, University of Tehran, the biochemical analysis were carried out in the University of Graz. SUBJECTS: Twenty-one male medical students were recruited by advertisement. Five subjects were dropped out due to lack of the compliance. METHODS: One group of Iranians received 30 mg/d beta-carotene and placebo for alpha-tocopherol; the other received beta-carotene plus 400 IU alpha-tocopherol for ten weeks. Concentrations of antioxidants in plasma and low density lipoproteins (LDL), plasma lipid profile, autoantibody against oxidized LDL (oLAb) and malondialdehyde (MDA) concentrations in plasma were measured. Oxidative resistance of LDL was estimated using conjugated diene assay. RESULTS: Iranians had a significantly lower plasma levels of total cholesterol (P < 0.002), LDL-cholesterol (P < 0.01) and high density lipoprotein-cholesterol (P < 0.002), compared to healthy Austrian subjects (n = 13). Although the baseline concentrations of alpha-tocopherol and beta-carotene were comparable with Austrians, lycopene, canthaxanthin and lutein were significantly higher in Iranians (P < 0.03-0.001). In vitro oxidative resistance of LDL, measured as lag-time, was slightly higher (P < 0.01) in Iranians comparing with Austrians. Plasma MDA and oLAb concentrations were significantly higher in Iranians (P < 0.001). Both dietary supplementations reduced plasma MDA concentrations (P < 0.001-0.001). A key finding was that a supplement combined with alpha-tocopherol caused also a significant increase of oLAb concentration (P > 0.01) as well as the significant increase of lag-time (P > 0.005). CONCLUSIONS: This study shows that high plasma MDA level of Iranians can be decreased by beta-carotene supplementation with or without alpha-tocopherol. However, alpha-tocopherol is a more powerful antioxidant, which can increase the resistance of LDL to oxidation, reduce the MDA concentrations in plasma and increase autoantibodies to oLDL.