Evaluation of the use of beta-sitostanol as a nonabsorbable marker for quantifying cholesterol absorption.

Summary For over a decade investigators have quantified cholesterol absorption by comparison of dietary intake and fecal excretion of isotopic cholesterol with that of &sitosterol as a "nonabsorbable" marker. However, &sitosterol might not be ideal due to its potential for absorption. We therefore carried out two studies to evaluate a new marker with less potential for absorption, [3H]~sitostanol. In the first study (Study I, n = 22). we compared absorption of [3H]~sitostanol and [ 4C]Psitosterol in a simultaneous dual-label continuous feeding ("phytosterol absorption") experiment. We observed a consistently higher ratio of [3H]~sitostanol/['4C]&sitosterol in the stool relative to diet on the first day of fecal collection (6.1% f 3.2% loss of [3H]bsitosterol, range 3-12%), but thereafter, the ratio in stool was similar to that in diet. In Study I1 (n = 23), we compared cholesterol absorption directly using [3H]&sitosterol and ['4C]cholesterol, and, separately, [3H]&sitostanol and ['4C]cholesterol. We found that mean absorption between the two methods was similar (45% k 11% versus 44% f lo%, respectively, P difference = 0.40), and the two methods correlated well with one another (r = 0.83) when samples from all available days were used. Variability between the two methods was greater in individuals who absorbed more than 40% of cholesterol. Cholesterol loss on day 2 estimated from use of bsitostanol as a nonabsorbable marker was predictive of absorption using ratios from days 4-6 (r = 0.80). These results suggest that, for the majority of subjects, Psitosterol is a valid nonabsorbable marker for cholesterol absorption.-Terry, J. G., B. L. McGill, and J. R. Crouse III. Evaluation of the use of psitostanol as a nonabsorbable marker for quantifying cholesterol absorpti0n.J Lipid Res. 1995.36: 2267-2271.