METABOLISM OF BILE-SALTS BY ALIMENTARY BACTERIA DURING TRANSIT IN THEHUMAN SMALL-INTESTINE

High numbers of alimentary bifidobacteria and lactobacilli survive the ir passage through the intestine. A majority of strains of Bifidobacte rium and Lactobacillus can deconjugate or dehydroxylate bile salts. Ou r aim was to study whether the ingestion of a fermented milk (FM) cont aining bifidobacteria and L. acidophilus could influence the metabolis m of bile salts in the small bowel. The study was randomised and doubl e blinded. Eight ileostomy subjects received on two consecutive days t he same meal plus a 100 g cup of an FM which either contained 10(7) CF U/g Bifidobacterium sp. and 10(8) CFU/g L. acidophilus, or had been pa steurised (as control). Ileal effluents were collected for 6h after me als. Effluent weight and excretion of the different bile salts were me asured. These did not differ significantly between the two periods exc ept ileal excretions of free and secondary bile salts which were signi ficantly increased during the FM period. Rapid and extensive deconjuga tion of bile salts was observed during in vitro experiments with both strains, but no dehydroxylation was detected. Excessive metabolism of bile salts in the human small bowel can be detrimental, and we suggest that the absence or limited extent of bile salt transformation capaci ty of bacteria added to food should be a pre-requisite for labelling a product as GRAS (generally recognised as safe).