Diet and Bile Acid Metabolism

Influence of age, intestinal transit time, and dietary composition on fecal bile acid profiles in healthy subjects

Bacterial transformation of bile acids is possibly involved in colorectal carcinogenesis. In several epidemiological studies, the secondary bile acid concentration in feces is related to the incidence of colonic cancer. However, data on fecal bile acids in case-control studies are conflicting. We investigated the influence of age, intestinal transit time, and dietary composition on fecal bile acid profiles in healthy subjects of three different age groups (mean ages 22, 48, and 67 years). Fecal bile acids were analyzed by gas-liquid chromatography. The concentration of the major secondary fecal bile acids increased with advancing age and was significantly higher in elderly subjects, compared to young adults. The concentration in middle-aged persons was intermediate. Analysis of dietary constituents showed that the fat intake in the three groups was comparable. The dietary fiber intake in elderly subjects was significantly lower than in the other two groups. The former group did excrete less dry fecal material compared to both other groups. Dietary fiber intake was negatively correlated with the total bile acid concentration. Probably, a decrease in dietary fiber intake results in higher fecal bile acid concentrations with advancing age. From the findings of this study, it is obvious that matching for age is important when case-control studies concerning the role of fecal bile acids in colorectal carcinogenesis are conducted.

Effects of dietary butter fat on fecal bile acid excretion in patients with Crohn's disease on elemental diet

The excretion rate of fecal bile acids was determined by gas-liquid chromatography in nine patients with Crohn's disease and six healthy volunteers under two dietary conditions with different amounts of fat: during nasoduodenal tube feeding with a fat-restricted elemental diet containing approximately 1.5 g/day of fat, and during the addition of 50 g/day of butterfat by peroral administration. The fecal bile acid excretion rate on the elemental diet was significantly greater in the patients with Crohn's disease than in the healthy controls. With ingestion of the additional fat, the excretion rate was significantly increased in the patients with Crohn's disease, but not significantly changed in the healthy controls. The bile acid excretion rate in Crohn's disease correlated with fecal fat excretion, but not with either fecal weight or disease activity. These studies show that the amount of dietary fat represents an important consideration in the evaluation of bile acid malabsorption in Crohn's disease.

Decreased prevalence of gallstones in gastric cancer

The prevalence of gallstones and the frequency of previously performed cholecystectomy were examined in 498 autopsy subjects who had gastric cancer and their age- and sex-matched control subjects. The frequency of gallstones not treated by operation and previous cholecystectomy was significantly (p less than 0.01) lower in those with gastric cancer than in the matched-control subjects. It is not possible to determine on the basis of this study what the possible factors that cause this phenomenon are.

Serum lipids, biliary lipid composition, and bile acid metabolism in vegetarians as compared to normal controls

Since dietary factors have been implicated in various diseases, such as coronary heart disease, gallstone formation and colonic cancer, possibly by affecting cholesterol and bile acid metabolism, we studied serum lipid levels, biliary lipid composition, cholic acid and deoxycholic acid kinetics in a group of young healthy male vegetarians and in age, sex and weight matched control subjects. Daily intake of nutrients was higher with respect to polyunsaturated fatty acids, carbohydrates and dietary fibre in the vegetarian group. Although mean serum lipid levels in the vegetarian were 8-28% lower than in the control subjects, differences were not statistically significant. Biliary lipid and biliary bile acid composition were similar in both groups. Bile acid kinetics, measured after simultaneous injection of [3H]cholic acid and [14C]deoxycholic acid, showed a slightly lower output of cholic acid and a slightly higher input of deoxycholic acid in the vegetarians, this causing a significantly (P less than 0.025) higher 7 alpha-dehydroxylation fraction (input deoxycholic acid divided by synthesis of cholic acid) in the vegetarians. Our results in young males suggest that bile acid conservation is associated with a vegetarian diet, but do not support the supposition that a vegetarian diet reduces deoxycholate formation.