Influence of dietary casein and soy protein isolate on intestinal cholesterol and bile acid concentration.

This study reports quantitative and qualitative differences in intestinal bile acids and cholesterol in miniature pigs following dietary casein or soy protein isolate. The total amount of bile acids in the small intestine was significantly higher when soy protein isolate was fed in comparison to casein. The values were (mean +/- SEM) 4.51 +/- 0.39 mmol and 2.43 +/- 0.08 mmol, respectively, when the proteins were given as the sole component of the diet. When the proteins were given as part of a semi-purified diet, these values were 6.44 +/- 1.04 mmol and 3.95 +/- 0.39 mmol, respectively. Hyocholic acid amounted to 39.6%, hyodeoxycholic acid to 31%, and chenodeoxycholic acid to 27.6% of total bile acids in the small intestine when casein was fed. The soy-fed animals tended to have more secondary bile acids. The total small bowel chymus content, on a wet weight basis, was 63% higher in the soy group. In all experimental conditions studied, there was a close correlation between small bowel chyme content and bile acid content. The distribution of bile acids in the small intestine showed that the soy fed animals tended to have more bile acids in the distal parts of the jejunum. The intestinal cholesterol contents were not significantly different between dietary groups.