Effect of type of dietary fat and cholesterol on cholesterol absorption rate in squirrel monkeys

To explore the effect of the type of dietary fat and the level of cholesterol on the rate of cholesterol absorption, 13 different male squirrel monkeys were used for 39 different tests. The plasma isotope ratio technique of Zilversmit, which involved the injection of 3H-cholesterol and gastric intubation of 14C-cholesterol, was shown to give reproducible results which compared well with those based on a method involving labeled beta-sitosterol. The percentages of ingested cholesterol that were absorbed showed considerable variation among individuals, but were relatively constant in the same animal. Safflower oil, a highly unsaturated fat, promoted a higher rate of cholesterol absorption than butter, regardless of the level of dietary cholesterol. The rate of cholesterol absorption was a constant percentage of that fed regardless of the absolute level of cholesterol in the habitual diet or the test meal (up to 218 mg or 5+ mg/kcal). Even at low levels of dietary cholesterol the percent absorption is greater in squirrel monkeys than in man.