Serum plant sterols and their relation to cholesterol absorption.

beta-Sitosterol and campesterol were measured in serum lipoproteins of 17 subjects from two families. The serum levels of the two phytosterols were closely correlated with each other (r = 0.974), less consistently with serum cholesterol (r = 0.489), and not at all with serum triglycerides. As compared to cholesterol, serum free and esterified phytosterols tended to be accumulated in HDL where the phytosterol/cholesterol ratios were almost 40% higher than in VLDL and LDL. The serum phytosterol concentrations, the phytosterol/cholesterol ratios, especially in VLDL and LDL, and the fractional absorption of cholesterol were higher in women than in men. The levels of the phytosterols in whole serum and in each lipoprotein were significantly correlated with the percentage absorption of dietary cholesterol but were independent of the amount of dietary cholesterol and plant sterols. Our findings suggest that, in general, serum levels of noncholesterol sterols are effectively determined by the absorption which in turn is proportionate to the fractional absorption of cholesterol.