The effect of dietary fat on the turnover of cholic acid and on the composition of the biliary bile acids in man.

Abstract

The effects on the bile-acid composition in bile of saturated fat (coconut oil) and of non-saturated fat (corn oil), contained in either fat-rich liquid formula diets (60% of calories as fat) or in solid diets, were determined in 11 human subjects. Metabolism of cholic acid was also studied after oral administration of cholic acid-24-C14. Replacing coconut oil with corn oil in all cases produced the expected depression of serum cholesterol concentration. The ratio of bile acid conjugates with glycine to those with taurine and the relative contribution of cheno-deoxycholic acid to the mixture of bile acids found in bile were lower on liquid formula than on solid diets with both dietary oils. On corn oil, the relative concentration of chenodeoxycholic acid was generally lower than on coconut oil in otherwise identical diets. There were no consistent changes in the pool size of cholic acid, either on transition from a solid to a liquid diet or with changes in the type of fat. In 4 subjects, the daily turnover of cholic acid was greater on corn oil-containing diets than on coconut oil-containing diets that were otherwise identical. In 3 other subjects, however, there was little or no change in cholic acid output, even though the changes in serum cholesterol were comparable in magnitude to those showing a change in cholic acid turnover. In 2 additional subjects, transition from a solid diet to a formula diet was associated with large changes in serum cholesterol level that were parallel, rather than reciprocal, to changes in cholic acid turnover. The results as a whole, therefore, lend no support to the proposition that changes in cholesterol level brought about by manipulation of dietary fat are necessarily due to or correlated with reciprocal changes in turnover rates of cholic acid.