The Absorption of Plant Sterols and Their Effect on Serum and Liver Sterol Levels

Abstract
Rats were fed synthetic diets containing 25% of oleic acid, 1% of sodium taurocholate, and 2% of soybean sterols in various combinations. The sterol intake was accurately measured and fecal sterol excretion was determined gravimetrically. On a fat-free diet virtually all of the plant sterols could be quantitatively recovered in the feces. When 1% of sodium taurocholate was added to the fat-free diet, 15.7% of the sterols ingested were absorbed (25 mg/day). Addition of 25% of oleic acid to the basal diet also promoted the absorption of the plant sterols (15.5% of the amount fed, or 24 mg/day). Maximum plant sterol absorption, 22.9% of the total amount fed (40 mg/day), occurred when 25% of oleic acid and 1% of sodium taurocholate were added to the basal diet. The absorbed plant sterols had very little effect on the liver sterols. At most a slight increase was observed in the group exhibiting maximum plant sterol absorption. The serum sterols increased in the groups fed plant sterols with oleic acid or oleic acid and bile salts. The addition of oleic acid and bile salts to the diet produced the highest elevation of the serum sterols (104.4 mg %). No plant sterols could be detected by chromatography (at the 5% level) in the groups fed plant sterols. The data in the present study suggest that plant sterols are absorbed through the same mechanism as cholesterol and that plant sterols may be converted to cholic acid, cholesterol, or a cholesterol intermediate in the intestine or liver.

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