Book Description

"Phytosterols play an important role in nature and as synthetic supplements for the modification of cholesterol metabolism in humans. The consensus is that the primary mechanism by which phytosterols modify lipid profiles is through altering the absorption of cholesterol. This thesis examined the effects of phytosterol mixtures on (i) de novo cholesterol synthesis rates and appearance of de novo cholesterol into the cholesterol ester pool through the use of deuterium incorporation, as well as, (ii) plasma lipid and sterol concentrations in normolipidemic humans. The initial investigation of this thesis compared the effects of diets based on either corn oil, olive oil, or olive oil plus phytosterol mixture on cholesterol metabolism. Each treatment was administered for 10 days in a cross-over design to 16 normolipidemic humans. In addition to confirming prior conclusions that corn oil was more effective than olive oil at decreasing plasma total and LDL-cholesterol concentration, this study was one of the first to determine that the differential effects on cholesterol metabolism observed in humans consuming corn versus olive oil is due, in part, to the higher concentrations of plant sterols naturally found in corn oil. The second study presented in this thesis investigated the differential effects on sterol metabolism of phytosterol mixtures either enriched with sitostanol or sitostanol-free administered for 10 days in 11 normolipidemic humans. The results of this study demonstrated that only the phytosterol mixture containing low doses of sitostanol decreased plasma total and LDL-cholesterol concentrations and increased the circulating HDL/LDL ratios; thus, the sitostanol-enriched phytosterol mixture was a more effective cholesterol-lowering agent." --