Effect of dietary proteins and/or their digestive products on intestinal taurocholate absorption.

[14C]Taurocholate was orally administered to rats together with a definite amount of either casein- or soy protein-based diet and its postprandial movement along the digestive tract was investigated. A difference was observed between both dietary groups in intraluminal transit as well as mucosal accumulation of [14C]taurocholate in the ileum; namely the soy protein intake led to a decrease in the bile acid incorporation into the ileal mucosa relative to the casein intake, although raising its intraluminal stay. In addition, the digestive products from these and other food proteins by pepsin-pancreatin digestion (peptides with molecular weights of more than 1,000) were examined for their inhibitory effects on in vitro absorption of taurocholate with ileal everted sacs. As the digestive product affinity for taurocholate increased, the rate of taurocholate absorption decreased. It thus seems likely that a food protein more abundant in hydrophobic peptides following intraluminal digestion adsorbs much more bile acids in the gut, thereby disturbing their intestinal absorption.