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Are Phytosterol Supplements Safe?

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Updated July 01, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: Are Phytosterol Supplements Safe?
Answer:

Phytosterols, or plant sterols, have been touted for their ability to help lower LDL cholesterol levels. Some studies have noted up to a 20% decrease in LDL levels when taking anywhere between 3 and 5 grams of phytosterols every day. Many manufacturers have also taken notice, placing phytosterols in many foods -– such as spreads and snacks -– as well as vitamins. But are they safe to take for a long period of time?

Although there are many short-term studies that suggest phytosterols can lower LDL, not enough studies have been conducted to examine the long-term effects of phytosterol supplementation in humans. For the most part, phytosterols are well-tolerated when first started, with only some individuals experiencing side effects such as constipation, bloating, or an upset stomach.

However, the studies looking at the potential effects of long-term exposure to phytosterol supplementation are very few –- and conflicting. Some studies have stated that a high intake of phytosterols could not only reduce your LDL -- it could also have a neutral effect or lower your risk for heart disease. On the other hand, there are a handful of studies that suggest that consuming a lot of phytosterols long-term could increase your risk in developing heart disease.

The thought that phytosterols could contribute to atherosclerosis mostly comes from observations in humans and animals consuming phytosterols with a condition called sitosterolemia. Sitosterolemia, or phytosterolemia, is a rare, inherited condition that causes increased absorption of phytosterols (primarily sitosterol) in the blood, causing them to accumulate in the body and deposit within arteries. In these studies, increased phytosterol intake in mice and rats resulted in acceleration of the formation atherosclerotic plaques containing sitosterol. One study noted that an increased concentration of sitosterol in the blood also resulted in an increased incidence of cardiovascular events in men who already had heart disease.

Additionally, it is thought that long-term consumption of foods supplemented with phytosterols may cause a modest decrease in the absorption of certain fat-soluble vitamins and antioxidants, such as beta-carotene, over time.

Because the studies examining these factors are conflicting, more information would be needed to determine exactly what problems, if any, could result from consumption of phytosterol-supplemented foods and vitamins over a long period of time.

So, if you are considering taking phytosterol supplements or foods supplemented with phytosterols, but are concerned about the lack of information on long-term safety, you can consider getting your phytosterols naturally from foods such as fruits, vegetables, nuts and whole grains. Until more is known about long-term phytosterol supplementation, the Nutrition Committee of the American Heart Association recommends that phytosterols -– whether supplemented with a pill or in food -– should only be used in individuals who have high total cholesterol and/or LDL cholesterol levels.

Sources:

Malinowski JM and Gehret MM. Phytosterols for dyslipidemia. Am J Health Syst Pharm 2010;67;1165-1173.

Micromedex Healthcare Series [internet database]. Greenwood Village, CO: Thomson Reuters (Healthcare) Inc. Updated periodically.

Pinedo S, Vissers MN, Von Bergmann K et al. Plasma levels of plant sterols and the risk of coronary artery disease: the prospective EPIC-Norfolk Population Study. J. Lipid Res. 2007. 48: 139–144.

Strandberg TE, Gylling H, Tilvis RS, et al. Serum plant and other noncholesterol sterols, cholesterol metabolism and 22-year mortality among middle-aged men. Atherosclerosis 210 (2010) 282–287.

Lichtenstein AH, Deckelbaum RJ. Stanol/sterol ester–containing foods and blood cholesterol levels: a statement for healthcare professionals from the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation. 2001;103:1177-1179.

Assmann G, Cullen P, Erbey J, et al. Elevation in plasma sitosterol concentration is associated with an increased risk for coronary events in the PROCAM study. Circulation 2003;108(Suppl.):3300.

Sutherland WHF,Williams MJA, Hye ER, et al. Association of plasma noncholesterol sterol levels with severity of coronary artery disease. Nutr Metab Cardiovasc Dis 1998;8:386–91.

Fassbender K, Lutjohann D, Dik MG, et al. Moderately elevated plant sterol levels are associated with reduced cardiovascular risk—the LASA study. Atherosclerosis 196 (2008) 283–288.

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