What Are Phytosterols?
Phytosterols, also known as plant sterols, are a class of compounds found in all plants. These compounds are structurally similar to cholesterol found in animals, and they play much the same role--helping to maintain cell-membrane structure.
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Natural Food Sources
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While phytosterols are found in all plants, the richest natural sources of the compound are vegetable oils, nuts, legumes and whole grains. Fruits and vegetables usually have lower concentrations. A 2002 Washington University in St. Louis study found that the average daily intake of phytosterols through diet is 167 to 437 mg. It is believed that early humans may have consumed as much as 1 g of phytosterols per day.
Phytosterol-Enriched Foods
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In recent years a number of phytosterol-enriched margarines, each promising to reduce cholesterol levels, have hit the market. These products, which have been approved by the U.S. Food and Drug Administration, provide up to 2 g of plant sterols per serving--well beyond what is normally consumed through diet. Phytosterols have also been added to a variety of other food products, including yogurt, fruit juices, snack bars and chips.
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Heart Disease
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A meta-analysis published in the March 25, 2000, British Medical Journal found that consumption of margarine spreads fortified with 2 g of phytosterols reduced low-density lipoprotein (LDL) cholesterol levels by an average of 9 to 14 percent. This drop in LDL is estimated to reduce the risk of heart disease death by about 25 percent. High density lipoprotein (HDL) cholesterol and triglyceride levels were unchanged. Sterols appear to work by reducing the ability of cholesterol to be absorbed into the bloodstream.
Cancer
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Research into the effects of phytosterols on cancer risk have shown conflicting results. A 2000 Uruguayan study found that a diet high in plant sterols reduces the risk of developing stomach cancer. A 2001 study from the Netherlands failed to find any association between phytosterol intake and colon and rectal cancer risk.
Warning
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While plant sterols are generally regarded as safe, a study published in the July 2008 Journal of Lipid Research found that phytosterols can accumulate in heart valves, potentially leading to a condition known as aortic valve stenosis. It is not known whether individuals who use products enriched with phytosterols are at a higher risk of developing this condition. Current recommendations suggest keeping daily intake of phytosterols below 3 g per day.
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References
Resources
- Photo Credit image by Quadell
