Effect of low-fat, high-fat, and fiber-supplemented high-fat diets on colon cancer risk factors in feces of healthy subjects.

Normal healthy volunteers (n = 8) received low- and high-fat (14% and 53% energy/day, respectively) and dietary fiber-supplemented high-fat diets (fiber 25 g/day, fat 52% energy/day) for 10 days each. Colon cancer risk factors in feces were measured by colonic nuclear aberration assay, the Ames Salmonella test using strain TA100, and measurement of bile acids and calcium soaps. Nuclear aberrations in colonic epithelium increased during the high-fat diet period and then decreased during the fiber-supplemented high-fat diet period. There were no significant differences in the mutagenicity on Salmonella TA100 or in the concentration of bile acids during the high-fat diet period. Bile acids decreased during the fiber supplementation period. The marked increase in calcium soaps during the high-fat diet period indicates an increase in long-chain fatty acids in the fecal lipid component and conversion of these fatty acids to insoluble calcium soaps when enough calcium is present.