Lack of effect of chronic administration of oral beta-carotene on serum cholesterol and triglyceride concentrations. Previous studies suggest that chronic oral administration of retinol and other retinoids causes elevation of plasma triglyceride concentrations. The effects of chronic oral administration of beta-carotene, a carotenoid partially metabolized to retinol, on plasma lipid concentrations have not been well studied; therefore, we studied 61 subjects over 12 mo while they were enrolled in a skin-cancer-prevention study in which patients were randomly assigned to receive either placebo (n = 30) or 50 mg beta-carotene/d orally (n = 31). At study entry and 1 y later, fasting blood samples were obtained for measurement of triglycerides, total cholesterol, HDL cholesterol, retinol, and beta-carotene. Retinol concentrations changed minimally in both groups; beta-carotene concentration increased an average of 12.1 +/- 47 nmol/L in the placebo group and 4279 +/- 657 nmol/L in the active-treatment group. Both groups experienced similar small increases in triglyceride and total cholesterol concentrations and small decreases in HDL cholesterol. Daily oral administration of 50 mg beta-carotene/d did not affect plasma lipid concentrations. 