Cholesterol absorption in primates as determined by the Zilversmit isotope ratio method

The Zilversmit isotope ratio method for measuring cholesterol absorption has been applied to baboons (Papio ursinus) and vervet monkeys (cercopithecus aethiops pygerethrus) and found to compare well with the more complicated method involving fecal excretion. Cholesterol absorption in the baboon was found to be 26.3% by the Zilversmit method and 22.2% by the fecal excretion method. In vervet monkeys the Zilversmit method showed 26.9% absorption as compared with 29.1% by the other. Sitosterol degradation (which is used to assay degradation) was found to be 64.1 and 69.3% in monkeys and baboons, respectively. Sitosterol degradation is about 5% in rats (1) and 23–27% in man (8). The correction for sterol degradation must, therefore, be determined for each species (and possibly in each experiment).