Diet and Excretionof Bile Acid&

Reddy and Wynder (13) investigated fecal bile acids and neutral sterols of various population groups: North Americans consuming a high-fat, mixed western diet; North American Seventh-Day Adventists consuming a diet without meat and moderately low amount of fat; Japanese on a low-fat diet; Chinese consuming low-fat Chinese diet; and strict vegetarians consuming a low-fat vegetarian diet. A significant increase in the excretion of secondary bile acids (deoxycholic acid, litho cholic acid and 12-ketolithocholic acid) and cholesterol metab olites (mainly coprostanol and coprostanone) was observed in North Americans consuming a high-fat mixed western diet, compared with other groups(1 3). Metabolic studies comparing a high-meat, high-fat diet with a meatless, low-fat diet showed that the former resulted In elevated levels of fecal deoxycholic acid, lithocholic acid, coprostanone, and coprostanol (11). Protein content was essentially the same, but the fat content was altered in these diets. Hentges et al. (5) compared diet series in which fat content was kept constant, but protein content altered, consisting of a control diet, a high-beef diet, and a meatless diet. There was no increase in the concentra tions of bile acids in the feces of subjects during the high-meat diet. These data indicate that high animal-protein consumption produces no major effect on bile acid excretion. Hill (6), after review of several studies, also concluded that it is the fat, not the protein content, in the meat that determines the effects on the fecal steroids. Recently, we have undertaken a study in which we compared the fecal excretion of bile acids in healthy subjects consuming a customary high-fat, mixed western diet and an experimental high-fat, high-beef diet. The protein contents of all diets were the same, but the fat content was about 25% higher in experi mental diets than in customary mixed western diet. The con centration of total bile acids, as well as secondary bile acids (deoxycholic acid and lithocholic acid) was higher during the period of consumption of experimental high-fat, high-beef diet compared to customary mixed western diet period (Table 1). In order to understand the specifics of the mechanisms whereby dietary fat influences colon cancer, the effect of type and amount of fat on biliary and fecal bile acid pattern was studied in rats (9). Biliary excretion of cholic acid, /3-muricholic acid, ursodeoxycholic acid, and deoxycholic acid was higher in rats fed a diet containing20% corn oil or 20% lard than in rats fed diets containing 5% corn oil or 5% lard. High-fat (corn oil or lard) intake was also associated with an increased excre tion of fecal deoxycholic acid, lithocholic acid, and 12-keto deoxycholic acid. Type of fat had no effect on biliary and fecal bile acid excretion. The higher biliary and fecal bile acid con centration during the intake of high dietary fat could be the result of increased bile acid synthesis in the liver. The above studies, both in humans and in animals, have shown the importance of the Interaction of high-fat diet and the production of bile acids potentially relevant in the etiology of large bowel cancer (14). Abstract