Comparison of absorption and metabolism of beta-sitosterol and beta-sitostanol in rats

The fates of [4-14C]beta-sitosterol ([14C]S) and [4-14C]beta-sitostanol ([14C]HS) were compared after after oral or intravenous administration to rats. Excretion into feces of oral [14C]HS was significantly higher than that of [14C]S. More than 97% of [14C]HS and 88% of [14CS]S were recovered in the feces within 7 days. Thus, deposition of [14C]HS was negligible in the tissues that were examined. Turnover in serum of [14C]HS which was injected intravenously appeared to be more rapid than that of [14C]S; [14C]HS was excreted as neutral steroids at a rate more than twice that of [14C]S. The rate of excretion of [3H]cholesterol was slightly greater when HS was administered simultaneously. The liver contained significantly less radioactivity after [14C]HS than after [14C]S administration. More [14C]HS than [14C]S was present in esterified form in serum and liver. The ratio of sterol in very low density lipoprotein to that in high density lipoprotein was less for HS or S than for endogenous cholesterol; this was particularly marked with HS. These results suggest that HS would be a more effective hypocholesterolemic agent than S.