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.

Non-esterified plant sterols solubilized in low fat milks inhibit cholesterol absorption--a stable isotope double-blind crossover study.

BACKGROUND: The cholesterol absorption inhibiting properties of plant sterols in milks are unknown. The milk fat globule membrane components may enhance the absorption of cholesterol and could make plant sterols less efficient in this complex matrix. AIM OF THE STUDY: To evaluate in hypercholesterolemic men the cholesterol absorption inhibiting properties of verified properly solubilized, non-esterified plant sterols in partly vegetable oil containing milks. METHODS: The plant sterols in milk were determined to be properly solubilized, and to have effective in vitro functionality. Sixteen hypercholesterolemic adult men (initial total cholesterol 5.8-8.6 mM) then consumed milk containing sterols (1.8 g of non-esterified pure plant sterols/d) and control milk, alternatively, during two 6-day periods in a double blind cross over design. During the trial, cholesterol absorption was evaluated from the ratio of plasma isotopic enrichment of [26, 26, 26, 27, 27, 27-(2)H(6)]cholesterol from oral intake (35.6 +/- 0.2 micromol, +/- SEM) over enrichment of [23, 24, 25, 26, 27-(13)C(5)]cholesterol from intravenous injection (77.9 +/- 0.5 micromol). RESULTS: Plant sterols in low fat milks contained very few crystals > 11 microm in the presence and absence of bile salts and lysophospholipids, and inhibited cholesterol uptake in Caco-2 cell. This assured that the sterols were properly solubilized prior to the clinical trial. In the clinical study, compliance of volunteers was excellent. After tracer injections (72 h), the plasma [(2)H] and [(13)C] isotopic enrichments changed from 0.024 +/- 0.001 and 0.072 +/- 0.003 MPE (control) to 0.015 +/- 0.001 and 0.074 +/- 0.002 MPE during sterol treatment, respectively. Cholesterol absorption was reduced from 70.1 +/- 4.2 % with control to 41.1 +/- 4.0 % with milks containing plant sterol (P < 0.001). CONCLUSIONS: These results demonstrate that properly solubilized non-esterified plant sterols in milks significantly inhibit cholesterol absorption in mildly hypercholesterolemic men.