Sitostanol administered in lecithin micelles potently reduces cholesterol absorption in humans

Background: Phytosterol feeding in human clinical trials has had generally small and inconsistent effects on serum cholesterol concentrations, raising doubts about the importance of phytosterols in natural diets and supplemen ts. Objective: The hypothesis tested was that the low intestinal bioavailabilit y of purified phytosterols can be increased by formulation with lecithin. Design: The ability of sitostanol to reduce cholesterol absorption was meas ured directly by including hexadeuterated cholesterol tracer in a standard test breakfast and measuring plasma tracer concentration 4 and 5 d later by gas chromatography-negative ion mass spectrometry. The tracer amount after a test meal containing sitostanol was compared with that after an identica l meal containing placebo. Each subject served as his or her own control an d the order of testing was random. Sitostanol was formulated either as a po wder or as a sonicated micellar solution with lecithin. A total of 38 singl e-meal tests were performed in 6 healthy subjects. Results: Sitostanol powder(1 g) reduced cholesterol absorption by only 11.3 +/- 7.4% (P= 0.2), confirming in vitro data showing poor solubility of sit ostanol powder in artificial bile. In contrast, sitostanol in lecithin mice lles reduced cholesterol absorption by 36.7 +/- 4.2% (P = 0.003) at a dose of 700 mg and by 34.4 +/- 5.8% (P = 0.01) at a dose of 300 mg. Conclusions: Sitostanol reduced cholesterol absorption at doses lower than reported previously, but only if presented in lecithin micelles. Properly f ormulated sitostanol as well as naturally occurring complexes of phytostero l and phospholipid might be therapeutically useful for cholesterol lowering .