Dietary phytosterols, which comprise plant sterols and stanols, reduce plasma Low-Density
Lipoprotein-Cholesterol (LDL-C) levels when given 2 g/day. Since this dose has not been reported to
cause health-related side effects in long-term human studies, food products containing these plant compounds
are used as potential therapeutic dietary options to reduce LDL-C and cardiovascular disease
risk. Several mechanisms have been proposed to explain the cholesterol-lowering action of phytosterols.
They may compete with dietary and biliary cholesterol for micellar solubilization in the intestinal
lumen, impairing intestinal cholesterol absorption. Recent evidence indicates that phytosterols may also
regulate other pathways. Impaired intestinal cholesterol absorption is usually associated with reduced
cholesterol transport to the liver, which may reduce the incorporation of cholesterol into Very-Low-
Density Lipoprotein (VLDL) particles, thereby lowering the rate of VLDL assembly and secretion.
Impaired liver VLDL production may reduce the rate of LDL production. On the other hand, significant
evidence supports a role for plant sterols in the Transintestinal Cholesterol Excretion (TICE) pathway,
although the exact mechanisms by which they promote the flow of cholesterol from the blood to enterocytes
and the intestinal lumen remains unknown. Dietary phytosterols may also alter the conversion
of bile acids into secondary bile acids, and may lower the bile acid hydrophobic/hydrophilic ratio,
thereby reducing intestinal cholesterol absorption. This article reviews the progress to date in research
on the molecular mechanisms underlying the cholesterol-lowering effects of phytosterols.
Keywords: Bile acids, cholesterol absorption, intestine, low-density lipoproteins, liver, phytosterols, TICE.
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