Dietary plant sterols: current status in human and animal sterol metabolism

Abstract

It is well established that plant sterols are absorbed to a certain extent by all animal species. Evidence is available to show that the absorption of C₂₈ sterol (campesterol) is higher than that of C₂₉ sterol (β-sitosterol). This finding suggests that great caution should be exercised in extrapolating absorption values for plant sterols by using mixtures of plant sterols. Tissue distribution of absorbed plant sterols closely parallels that of cholesterol and both sterols are subjected to similar metabolic reactions. The sitosterols are catabolized to the same steroid hormones as those formed from cholesterol. The plant sterols are converted into bile acids in the animal liver. The nature of bile acids depends mostly on the ability of the species to dealkylate the extra methyl or ethyl group present in the side chain. The fact that absorbed plant sterols are catabolized to a variety of products in animal tissues suggests that further work should be directed toward the effects of these products in cholesterol metabolism. These studies might explain the "extra absorptive" effect of sitosterols on serum cholesterol. Further studies should be carried out to determine whether the distribution of plant sterols in subcellular fractions and plasma lipoproteins is similar to that of cholesterol. The potential use of plant sterols as injectable hypocholesteremic agents depends on the available knowledge concerning the metabolic fate and the effects of plant sterols and their oxidation products in the animal body.