Identification and quantification of neutral fecal steroids by gas–liquid chromatography and mass spectrometry: studies of human excretion during two dietary regimens

The excretion of fecal neutral steroids was studied in six normocholesterolemic subjects and one hypercholesterolemic subject fed a standardized diet supplemented with butter fat or corn oil.The neutral steroids in the diets and in feces were identified by gas–liquid chromatography combined with mass spectrometric analyses of the chromatographic effluents. The three main sterols in the diets were cholesterol, Β-sitosterol, and a methylcholesterol, probably campesterol.The fecal neutral steroids were cholesterol and its metabolites, coprostanol and coprostanone, Β-sitosterol and methylcholesterol, and their corresponding metabolites. In addition small amounts of cholestanol, 24Β-ethylcholestanol, and methylcholestanol were present. Most subjects on both diets excreted coprostanol as the predominant fecal steroid. However, during the corn oil period the proportion of coprostanone and/or cholesterol was increased.When the normal subjects had been transferred from the butter fat to the corn oil diet the serum cholesterol level fell in all subjects. On the corn oil diet the mean total excretion of neutral steroids in feces increased significantly, primarily as a result of the elevated elimination of plant sterols and plant sterol metabolites. The mean total excretion of cholesterol and cholesterol neutral metabolites was 527 mg/day during the butter and 614 mg/day during the corn oil period. This change, however, was not statistically significant.The hypercholesterolemic subject responded in the same fashion as the normal subjects.The possible effect of the two diets on the excretion of “nondietary” cholesterol as neutral fecal steroids is discussed.