Sterol Balance in Man as Plasma Cholesterol Concentrations Are Altered by Exchanges of Dietary Fats*

Abstract

In 5 studies of 4 patients, fecal excretions of neutral and acidic steroids were measured before, during, and after plasma cholesterol concentrations were altered by exchanges of dietary fats. In 3 of 5 studies, sterol-free "synthetic" fats were fed; on saturated and unsaturated fat regimens the degree of saturation exerted a significant effect on plasma cholesterol concentration, independent of non-glyceride components. Quantification of the numerous excretion products of endogenous cholesterol was based on chemical isolation of the acidic and neutral steroids, and on measurement of these by titration and by weight, respectively. Completeness of recoveries was verified at all stages in terms of C14 -labelingof the two fractions, following the administration to all patients of 4-C14 -cholesterol. Changes in plasma cholesterol content (both increases and decreases) varied from 1300 to 6400 mg. However, no significant reciprocal changes in excretions of fecal steroids occurred as plasma cholesterol concentrations were made to vary. It seems likely that the immediate changes in plasma concentration were due to redistribution of cholesterol to other tissues.