Campestanol (24-methyl-5 alpha-cholestan-3 beta-ol) absorption and distribution in New Zealand white rabbits: Effect of dietary sitostanol

Campestanol (24-methyl-5 alpha-cholestan-3 beta-ol) is a naturally occurrin g plant stanol, structurally similar to cholesterol (5-cholesten-3 beta-ol) and widely distributed in vegetable oils consumed in human diets. We measu red the absorption and turnover of campestanol by the plasma dual-isotope r atio method and mathematical analysis of specific activity versus time deca y curves after simultaneous oral and intravenous pulse-labeling with [3 alp ha-H-3]- end [23-C-14]-labeled campestanol, respectively, in New Zealand Wh ite (NZW) rabbits: six fed chow and six fed chow with 125 mg/d campestanol end 175 mg/d sitostanol (24-ethyl-5 alpha-cholestan-3 beta-ol). Plasma conc entrations increased insignificantly from 0.08 +/- 0.01 to 0.09 +/- 0.01 mg /dL with dietary stanols. The percent campestanol absorption measured by th e plasma dual-isotope ratio method after the rabbits were fasted for 6 hour s yielded the percent absorption in the absence of competing intestinal ste rols and stanols and declined insignificantly from 11.6% +/- 3.5% in contro ls to 8.1% +/- 3.7% in the treated rabbit groups. In contrast, the turnover , which measured actual absorption averaged over 24 hours, increased from 0 .12 +/- 0.05 to 0.37 +/- 0.05 mg/d (P < .05) with campestanol and sitostano l added to the diet. However, the actual percent absorption declined from 3 % to 0.3% of dietary intake with the campestanol and sitostanol-enriched di et. Campestanol pool sizes, although remaining small, increased slightly fr om 1.1 +/- 0.4 to 2.5 +/- 1.5 mg. The removal constant (K-A) from pool A (M -A) did not change significantly with added dietary campestanol and sitosta nol (K-A= - 0.040 +/- 0.005 v -0.037 +/- 0.007 d(-1)). The results demonstr ate small campestanol plasma concentrations and body pools even when the ra bbits consumed substantial amounts because (1) intestinal absorption was li mited and (2) was further reduced by competing dietary sitostanol, and (3) campestanol was removed rapidly from the body. Thus, campestanol, which sha res the same basic structure and intestinal absorption pathway with cholest erol, does not accumulate when fed, and may be incorporated into the diet t o block cholesterol absorption. Copyright (C) 1999 by W.B. Saunders Company .