Gastrointestinal absorption and plasma kinetics of soy Δ⁵-phytosterols and phytostanols in humans

Abstract

Our objective was to measure the systemic absorption of lecithin-emulsified ⌬ 5 -phytosterols and phytostanols during test meals by use of dual stable isotopic tracers. Ten healthy subjects underwent two single-meal absorption tests in random order 2 wk apart, one with intravenous dideuterated ⌬ 5 -phytosterols and oral pentadeuterated ⌬ 5 -phytosterols and the other with the corresponding labeled stanols. The oral-to-intravenous tracer ratio in plasma, a reflection of absorption, was measured by a sensitive negative ion mass spectroscopic technique and became constant after 2 days. Absorption from 600 mg of ⌬ 5 -soy sterols given with a standard test breakfast was 0.512 Ϯ 0.038% for sitosterol and 1.89 Ϯ 0.27% for campesterol. The absorption from 600 mg of soy stanols was 0.0441 Ϯ 0.004% for sitostanol and 0.155 Ϯ 0.017% for campestanol. Reduction of the double bond at position 5 decreased absorption by 90%. Plasma t½ for stanols was significantly shorter than that for ⌬ 5 -sterols. We conclude that the efficiency of phytosterol absorption is lower than what was reported previously and is critically dependent on the structure of both sterol nucleus and side chain.

Dose-response effects of different plant sterol sources in fat spreads on serum lipids and C-reactive protein and on the kinetic behavior of serum plant sterols

“…In this situation, the terminal serum clearance t 1/2 is about 25 days while the half-life of the distribution phase from the rapid pool (t 1/2 only a few days) is in line with the findings by Ostlund et al (2002). Earlier experiments with radio-labeled sitosterol also showed a two-compartmental elimination behavior with comparable half-lives of 3.7 for the rapid phase but only 12.7 days for the terminal phase (Salen et al, 1970).…”

“…Experiments using the double-label method also showed an absorption of 0.5% for sitosterol and 1.9% for campesterol (Ostlund et al, 2002). This study using a single dose of 600 mg of sterols is clearly different from our chronic feeding study in which a total accumulated dose of about 100 g of PS has been delivered to the gut.…”

“…The study of Ostlund et al (2002) showed a t 1/2 for campesterol of 4.1 days in contrast to 2.9 days for sitosterol, which is probably again related to a different excretion rate from the hepatocyte into bile via ABCG5/G8 transporters. LDL carries much of the PS and its turnover of about 0.3 pools/day is in line with the acute single-dose PS disappearance studies (Shepherd et al, 1979).…”

“…The typical differences in PS composition from these sources could possibly influence the cholesterol-lowering efficacy or metabolic handling of the sterol. PS themselves are absorbed to minor degree, although the main site of action remains in the gut (Trautwein et al, 2003), whereas stanols, the fully hydrogenated form of sterols, are absorbed to a much lower extent (Ostlund et al, 2002). Results of different studies, testing whether sterol/ stanol mixtures influence each others absorption or excretion or metabolic effects are not conclusive (Normén et al, 2000;Nestel et al, 2001;Naumann et al, 2003).…”

Plant sterol or stanol consumption does not affect erythrocyte osmotic fragility in patients on statin treatment

“…Compared to cholesterol, only small amounts of plant sterols and stanols are absorbed by the intestine (Ostlund et al, 2002). Nonetheless, in patients on statin therapy, plasma plant sterol and stanol concentrations are two-fold increased .…”