A very low intake of fat is required to decrease fecal bile acid concentrations in rats.

The purpose of this study was to determine the effect of different amounts of dietary fat on colonic cell proliferation and fecal bile acid concentrations. Thirty-nine male Sprague-Dawley rats were randomly assigned to three diets (13 rats per diet) containing 5, 10 and 20 g butter/100 g diet. Diets were fed for 3 wk. As fat intake increased, total fecal fat excretion remained constant. When dietary fat was decreased from 20 to 10 g/100 g diet, total fecal bile acid concentrations tended to increase 14.5%. However, a further reduction to 5 g butter/100 g diet significantly decreased fecal total bile acid concentration by 48% from the concentration in feces of rats fed 10 g butter/100 g diet. The concentration of deoxycholate (considered a highly promotive bile acid) was not reduced unless the amount of fat in the diet was reduced to 5 g/100 g. Labeling index was used as an intermediate marker for colon carcinogenesis. For deoxycholate, a decrease of fat intake to 5 g/100 g diet decreased the cecal labeling index relative to those of rats fed 10 or 20 g butter/100 g diet. These data indicate that decreasing the dietary fat from 20 to 10 g/100 g does not decrease fecal bile acid concentration or colonic cell proliferation, but some effects are seen in rats fed 5 g butter/100 g diet.