Effects of beta-carotene supplementation on lipid peroxidation in humans

The ability of [beta]-carotene (BC) to reduce lipid peroxidation in humans was investigated. In this randomized double-blind controlled trial, 42 nonsmokers and 28 smokers received either 20 mg BC or placebo daily for 4 wk. Twenty-five smokers and 38 nonsmokers completed the trial. Changes in plasma BC concentrations increased significantly (P < 0.0005) and to the same extent in both groups supplemented with BC. There were no significant changes among the placebo groups. At baseline, lipid peroxidation measured by breath-pentane output (BPO) was significantly higher in the two smoking groups (BC: 8.8 [+ or -] 1.1, placebo: 9.4 [+ or -] 1.4 pmol [kg.sup.-1][multiplied by][min.sup.-1]) than in the nonsmoking groups (BC: 5.7 [+ or -] 0.5, placebo: 5.9 [+ or -] 0.6 pmol[multiplied by][kg.sup.-1][multiplied by][min.sup.-1]) (P < 0.005). BPO decreased significantly only in smokers receiving BC (6.5 [+ or -] 0.7 pmol[multiplied by][kg.sup.-1][multiplied by][min.sup < 0.04). Changes in breath-ethane output were not significant. Therefore, lipid peroxidation measured by BPO is significantly higher in smokers than in nonsmokers and is reduced by BC supplementation in smokers. There was no significant change (95% CI - 1.26, 1.12) in BPO when nonsmokers received BC.