Dietary stearic acid reduces cholesterol absorption and increases endogenous cholesterol excretion in hamsters fed cereal-based diets

The observation that dietary stearic acid does not raise plasma cholesterol concentration is well documented, although the regulating mechanisms are n ot completely understood. Therefore, we examined the effect of dietary stea ric acid on cholesterol absorption and sterol balance using male Syrian ham sters fed modified NIH-07 cereal-based diets selectively enriched in palmit ic acid (16:0), stearic acid (18:0), trans fatty acid (18:it), cis oleic ac id (18:lc) or linoleic acid (18:2). All diets contained 17 g/100 g total fa t and 0.05 g/100 g cholesterol; the five fat blends were enriched 30% with the fatty acid of interest above a constant fatty acid background. Choleste rol absorption efficiency was 50-55% in all treatment groups except for the 18:0 group, in which cholesterol absorption was significantly reduced to 2 1%. Plasma total cholesterol concentration was significantly lower in the 1 8:0 group compared to the 16:0 group. Fecal neutral steroid excretion was s ignificantly greater in hamsters fed the high 18:0 diet compared to the oth er treatment groups. After accounting for unabsorbed dietary cholesterol, e ndogenous cholesterol excretion was about 100% higher in the 18:0 group. Co nsequently, the calculated rate of whole body cholesterol synthesis was sig nificantly increased by dietary 18:0, Bile acid excretion accounted for onl y 12-20% of total sterol output by the hamsters in this study. Thus, the da ta suggest that reduced plasma cholesterol concentration in hamsters fed hi gh 18:0 diets may be influenced by reduced cholesterol absorption and incre ased excretion of endogenous cholesterol.