Metabolism of β-sitosterol in man

Abstract

A B S T R A C T The metabolism of P-sitosterol was compared to that of cholesterol in 12 patients. Sterol balance methods were supplemented by radiosterol studies, with the following results. (a) Plasma concentrations of P-sitosterol ranged from 0.30 to 1.02 mg/100 ml plasma in patients on intakes of 6-sitosterol typical of the American diet. Plasma levels were raised little when intakes were increased greatly, and on fixed intakes they were constant from week to week. On diets devoid of plant sterols, the plasma and feces rapidly became free of p-sitosterol. (b) The percentage of esterified P-sitosterol in the plasma was the same as for cholesterol. However, the rate of esterification of P-sitosterol was slower than that for cholesterol. (c) Specific activitytime curves after simultaneous pulse labeling with #-sitosterol-3H and cholesterol-"C conformed to twopool models. The two exponential half-lives of f-sitosterol were much shorter than for cholesterol, and pool sizes were much smaller. Values of turnover for ,8-sitosterol obtained by the sterol balance method agreed closely with those derived by use of the two-pool model. There was no endogenous synthesis of P-sitosterol in the patients studied; hence, daily turnover of P-sitosterol equaled its daily absorption. Absorption of P-sitosterol was 5% (or less) of daily intake, while cholesterol absorption ranged from 45 to 54% of intake. (d) About 20% of the absorbed f-sitosterol was converted to cholic and chenodeoxycholic acids. The remainder was excreted in bile as free sterol; this excretion was more rapid than that of cholesterol. (e) The employment of i3-sitosterol as an internal standard to correct for losses of cholesterol in sterol balance studies is further validated by the results presented here.

Comparison of the effects of plant sterol ester and plant stanol ester-enriched margarines in lowering serum cholesterol concentrations in hypercholesterolaemic subjects on a low-fat diet

“…All these ®ndings are in line with the ®ndings of earlier studies (Gylling et al, 1999a;Gylling & Miettinen 1999;Hallikainen et al, 2000;Jones et al, 1997Jones et al, ,1999Weststrate & Meijer, 1998). Besides the negligible absorption of plant stanols, the low serum concentrations could also result from fast and effective clearance of absorbed stanols (Salen et al, 1970).…”

“…Plant sterols are absorbed from 5% (sitosterol) to 15% (campesterol) (Heinemann et al, 1993;Salen et al, 1970). Furthermore, plant sterols and stanols may interfere with the absorption of carotenoids, as indicated by reduced serum carotenoid concentrations (Gylling et al, 1999b;Hallikainen et al, , 2000Hendriks et al, 1999;Weststrate & Meijer, 1998).…”

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

“…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). The 95% CI for the terminal-phase half-life is, however, large in our study.…”

Will recommended changes in fat and fibre intake affect cholesterol absorption and sterol excretion? An ileostomy study

“…Plant sterol excretion will re¯ect dietary intake, as the absorption of b-sitosterol, the major component of plant sterols, is very poor (Salen et al, 1970;Heinemann et al, 1993). A similar, although weaker correlation has been reported by Miettinen, who found a coef®-cient of correlation of 7 0.25 between dietary plant sterols, determined as faecal plant sterols, and fractional cholesterol absorption in 63 middle-aged men on self-selected diets (Miettinen & Kesaniemi, 1989).…”