Sterol and bile acid excretion in man and the effects of dietary fat.

Abstract

The fecal excretion of radioactive sterols and bile acids after intravenous injection of cholesterol-4-14C -labeled lipoproteins, prepared by in vitro incorporation of labeled free cholesterol into the patient''s serum, was studied in 6 subjects maintained on liquid formula diets providing 60% of calories as fat. The amounts of neutral and acidic metabolites of cholesterol that were excreted daily were calculated on the basis of radioactivities in the 2 fecal fractions and of serum cholesterol specific radioactivity (shown to equal the specific radioactivities of its metabolites). In all cases, the serum cholesterol levels were lower on diets containing unsaturated fat than with saturated fat. In 5 subjects the excretion of total metabolites of cholesterol ranged between 1 and 2 g daily on both diets, more than half of which were non-acidic materials (mostly sterols). The 6th subject differed from the rest in excreting up to 5.3 g of total metabolites daily and in increasing the sterols excreted from 1.2 g to 3.0 g on changing from saturated to unsaturated fat diet. For the group as a whole, however, there was no correlation between the hypocholesterolemic effect of unsaturated fat and changes in bile acid or sterol excretion.