Plant sterols and stanols

The expanding market of 'functional foods' containing plant sterols and stanols has focused interest on their cholesterol-lowering effects as well on possible adverse effects. Trials of cholesterol lowering demonstrate that intake of 2 g/day of plant sterols and stanols reduces serum low-density lipoprotein (LDL) cholesterol concentrations by approximately 10%. Safety concerns regarding elevations in serum plant sterol levels, or effects on fat-soluble vitamin absorption or hypothetical effects on serum sex hormone balance have received attention and been addressed in studies. Plant sterol (but not stanol) supplementation increased serum plant sterol concentrations but these levels remained much lower than those observed in homozygous sitosterolemia making an adverse health effect unlikely. Prolonged statin therapy also causes elevations in all cholesterol-adjusted plant sterol levels as well as small but significant elevations in serum unadjusted campesterol levels from baseline. This is probably caused by a statin-induced reduction in biliary cholesterol efflux resulting in a diminished intestinal cholesterol pool. The diminished competition with cholesterol molecules allows more plant sterol molecules to become incorporated in mixed micelles facilitating their uptake in enterocytes. With the exception of beta-carotene, reductions in serum concentrations of fat-soluble (pro)vitamins are usually abolished by adjustment for cholesterol suggesting that they reflect reductions in carrier lipoproteins, mainly LDL. The small reductions in serum beta-carotene are not regarded as a major concern, nor have any adverse effects on sex hormone metabolism been demonstrated apart from parenteral administration of large doses in experimental animals. However, as increasing consumer populations become exposed to a large variety of food products enriched with plant sterols and stanols the likelihood of rare adverse effects increases and surveillance is necessary.