Effects of tristearin, triolein and safflower oil diets on cholesterol balance in rats.

Diets containing relatively homogeneous triglycerides composed of 18-carbon chain saturated, monounsaturated or polyunsaturated fatty acids were fed to rats. Cholesterol absorption and turnover were studied. Cholesterol absorption was significantly less in rats fed tristearin than in animals fed triolein or safflower oil. Cholesterol removal from plasma was fastest in rats fed tristearin and slowest with safflower oil and triolein. Plasma cholesterol levels were lowest with tristearin and highest with safflower oil. Increased cholesterol in high density lipoproteins was observed with tristearin and triolein. Lymph and hepatic cholesterol, and lymph triglycerides were highest with safflower oil, suggesting endogenous mobilization. Cholesterol production was least with triolein. Sterol synthesis was greatest with tristearin, perhaps attributable to decreased negative feedback analogous to effects of cholestyramine. Differences in lipoprotein composition observed with the various diets are important since effects on particle size and shape may influence removal mechanisms. The mechanisms underlying the different effects of dietary triglycerides on sterol absorption and metabolism remain to be elucidated.