Effects of different types of dietary fiber preparations isolated from bamboo shoots, edible burdock, apple and corn on fecal steroid profiles of rats

Abstract

This study was conducted to evaluate the effects of different types of dietary fibers (DF) under the conditions with or without cholesterol (Chol) loading on the amount and composition of steroids in rat feces. Rats were fed Chol-unsupplied diets containing 10% lard and 5% DF preparation isolated from four kinds of food, bamboo shoots, edible burdock, apple and corn, for three weeks. The respective diets were supplemented with 0.5% Chol and then given to the rats for a further two weeks. The excretion of total bile acid (BA) and several major BAs increased significantly in the apple group with or without Chol loading when compared with that in the cellulose (CP) or other DF groups. The tendency in the apple group was more noticeable when the diet was supplemented with Chol. This is presumably a major reason for the tendency of decrease in serum and liver Chol concentrations in the apple group. The ratio of secondary BAs to total BA in the feces was significantly low in the apple group. Although the lithocholic acid (LCA)/deoxycholic acid (DCA) ratio, a risk index for colorectal cancer, was significantly lower in the bamboo, burdock and apple groups than in the CP or corn groups when given the diet without Chol, the differences disappeared with the addition of Chol. The proportion of coprostanol, a secondary metabolite of Chol, was smaller in the former three groups than in the CP or corn groups. These results suggest that the intake of some DF by host animals works beneficially for the microbial conversion of BA and Chol in the large intestine but that the addition of Chol acts to cancel such beneficial effects.