Fat Excretion The Influence of Dietary Fat on Fecal Fat Excretion

Abstract

Fat excretion was studied in two groups of rats following a 30-day period of conditioning during which the animals took diets containing either 15% tripalmitin or 15% olive oil as the only lipid. The two groups were then divided into subgroups, each of which was placed on one of 4 test diets for 10 days, during the last 7 of which feces were collected for analysis. The test diets included: a fat-free diet, a tripalmitin diet, a triolein diet, and a tripalmitin-trilinolein diet. The animals were sacrificed and analyses of the lipids in various body tissues were made. The lipid analysis of the samples obtained included: unsaponifiable matter, total fatty acids, melting point, neutralization equivalents, iodine value, fatty acid composition, and peroxide value. From the data obtained it is concluded that: The endogenous fecal fat was unaffected either in quantity or composition by the dietary fats used in these experiments. When tripalmitin-containing diets were fed, however, a considerable portion of the excreted fat represented unabsorbed dietary fat, whereas triolein appeared to be completely absorbed. Although the depot fats of rats were markedly different depending on whether they had been conditioned on tripalmitin or olive oil feeding, the composition of the depot fats, and changes in composition induced by dietary changes, exerted no influence on the composition of the endogenous fecal fat. Both of these findings support the view that endogenous fecal fat does not result from secretion of fat into the intestinal lumen, or from desquamation of epithelial cells of the intestinal mucosa, and hence are consonant with the view that endogenous fecal fat is synthesized by intestinal bacteria. The digestibility of tripalmitin when present as the sole fat in the diet was found to be increased by conditioning on a tripalmitin diet.