1. Male Wistar rats were fed on semi-synthetic diets containing cooked white kidney beans (Phaseolus vulgaris) or equivalent levels of protein and carbohydrate.
2. No change was observed in over-all nitrogen balance in animals fed on the bean diet, but there was a two-to three-fold increase in their faecal excretion, compared with control rats. This was compensated by a decrease in urinary-N excretion.
3. Homogenized small intestinal mucosa, prepared from bean-fed animals, showed at 28%increase in protein content compared with control material.
4. Measurements of 3H-labelled thymidine turnover indicated that mucosal cell exfoliation was increased by approximately 35% in the small intestines of bean-fed rats compared with controls.
5. It is concluded that though a diet rich in cooked P. vulgaris leads to someincrease in mucosal cell turnover in the small intestine of rats, the consequent increasein mucosal protein loss could not account for the increased faecal-N excretion seen in these animals.