Fecal cholesterol excretion studies in type II hypercholesterolemic patients treated with the soybean protein diet.

The fecal steroid elimination profile was studied in 7 type II hyperlipoproteinemic patients given a low-lipid diet with textured soybean proteins, in order to define the mechanism of the hypocholesterolemic activity of this new dietary regimen. Four of the patients followed a 3- + 3-week cross-over protocol, comparing the soybean diet with a reference low-lipid diet with animal proteins. In these, fecal neutral steroids and bile acids were analyzed by chromatography during the two dietary periods. In spite of the clear hypocholesterolemic effect, no significant differences in steroid output were noted between the two dietary periods. In the 3 remaining patients, a chromatographic + isotopic method (by injecting 14C-labelled cholesterol i.v. 4-6 weeks prior to the dietary study) was employed. Again, no marked changes were noted in the fecal neutral steroid and bile acid outputs and the slope of the decay curve of the plasma cholesterol-specific activity was not changed by the experimental diet, in spite of the remarkable decrease in plasma cholesterol. The reported results do not provide a definitive contribution to the mode of action of the soybean protein diet. They suggest, however, that it is not an effect mediated by undigestible dietary components. The possibility of a cholesterol redistribution from plasma to tissue pools should be considered.