Both free and esterified plant sterols reduce cholesterol absorption and the bioavailability of beta-carotene and alpha-tocopherol in normocholesterolemic humans

Background: Plant sterols reduce cholesterol absorption, which leads to a decrease in plasma and LDL-cholesterol concentrations. Plant sterols also lower plasma concentrations of carotenoids and alpha-tocopherol, but the mechanism of action is not yet understood. Objectives: The aims of this clinical study were to determine whether plant sterols affect the bioavailability of beta-carotene and alpha-tocopherol in normocholesterolemic men and to compare the effects of plant sterol esters and plant free sterols on cholesterol absorption. Design: Twenty-six normocholesterolemic men completed the double-blind, randomized, crossover study. Subjects consumed daily, for 1 wk, each of the following 3 supplements: a low-fat milk-based beverage alone (control) or the same beverage supplemented with 2.2 g plant sterol equivalents provided as either free sterols or sterol esters. During this 1-wk supplementation period, subjects consumed a standardized diet. Results: Both of the milks enriched with plant sterols induced a similar (60%) decrease in cholesterol absorption. Plant free sterols and plant sterol esters reduced the bioavailability of beta-carotene by approximately 50% and that of alpha-tocopherol by approximately 20%. The reduction in beta-carotene bioavailability was significantly less with plant free sterols than with plant sterol esters. At the limit of significance (P = 0.054) in the area under the curve, the reduction in alpha-tocopherol bioavailability was also less with plant free sterols than with plant sterol esters. Conclusions: Both plant sterols reduced beta-carotene and alpha-tocopherol bioavailability and cholesterol absorption in normocholesterolemic men. However, plant sterol esters reduced the bioavailability of beta-carotene and alpha-tocopherol more than did plant free sterols.