The hypocholesterolemic activity of beta-sitosterol and its hydrogenated product, beta-sitostanol (dihydrositosterol or stigmastanol) has been compared in young male rats. When cholesterol was included in the diet, sitostanol consistently exhibited significantly greater hypocholesterolemic activity than sitosterol. There were no apparent differences in the effects of the sterol and the stanol on the concentration of liver cholesterol and triglyceride. Increases in plasma triglyceride due to feeding sitosterol were not observed with sitostanol. Incorporation of dietary sitostanol into plasma, liver and other tissues was always negligible, and thus this stanol was almost completely recovered in feces, while there was considerable deposition of sitosterol (mean fecal recovery being 85% to 92%). The increase in fecal output of dietary cholesterol was significantly greater with the stanol than with sterol. There was no demonstrable negative effect on growth and weight of major visceral tissues in rats fed the sterol as well as the stanol. These observations together with those reported previously indicate that hydorgenation of phytosterols is a novel approach to enhance their hypocholesterolemic activities without influencing the relative safety of the initial sterols.

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Effects of dietary ƒÀ-sitosterol (S) and ƒÀ-sitostanol (HS) on the metabolism and fate of labeled cholesterol intravenously injected were compared in rats fed diets high in cholesterol. Kinetic behavior of the decay curve for serum cholesterol in the HS supplemented (C+HS)

Rats were fed plant sterols containing campesterol and beta-sitosterol in the differerent proportions, and their distribution in serum lipoproteins and in liver subcellular fractions was determined. In serum lipoproteins, the percentage as well as the concentration of plant sterols increased with the increase in the density of lipoproteins. Thus, high density lipoprotein (HDL) contained the highest and very low density lipoprotein (VLDL), the lowest. Also, there were distinct differences in the ratio of campesterol to sitosterol among lipoproteins, it was the highest in VLDL and lowest in HDL. Quantitatively, more than 75% of campesterol and 80% of sitosterol were carried in HDL; the values were significantly different from those of cholesterol (ca. 70%) in relation to total cholesterol. The distribution of plant sterols in liver subcellular fractions was virtually the same with that of cholesterol. Both nuclei and microsomes contained approximately 40% of total plant sterols.

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