Plant sterols and plant stanols are collectively known as phytosterols. Plant sterols are plant compounds with chemical structures similar to that of cholesterol. Especially high sterol levels are found in rice bran, wheat germ, corn oils, and soybeans. In a more concentrated form, these substances are called plant stanols. Structurally these compounds are chemically similar to cholesterol. However, unlike cholesterol derived from animal sources--which absorbs easily and raises the body's own cholesterol levels--phytosterols are present only at very low levels in the body because they are difficult to absorb.
Interestingly, phytosterols so closely resemble cholesterol that they can actually block food-based cholesterol from being absorbed into the bloodstream. The result is that both phytosterols and dietary cholesterol end up excreted in waste matter.
Recently food manufacturers have begun to incorporate plant sterols and stanols into such "functional foods" as vegetable oil spreads (Benecol or Take Control, for example). Nutritional supplement manufacturers also offer phytosterols in tablet form for those individuals who don't want the extra calories of cholesterol-lowering margarine.
Concentrated extracts of another phytosterol called beta sistosterol have been tested for lessening such discomforts of benign prostatic hyperplasia (BPH) as frequent and painful urination (see the library entry on beta-sistosterol for more detailed information).
Health Benefits
Because of their ability to block dietary cholesterol absorption, phytosterols can help lower your cholesterol levels. In the last few years, clinical research has also discovered other effects, including reducing symptoms of an enlarged prostate, improving the control of blood sugar among people with diabetes, and reducing inflammation among patients with autoimmune diseases such as rheumatoid arthritis and lupus.
Because much of this research is still in a preliminary phase, nutritionally oriented physicians are currently recommending phytosterols only for prostate disorders and cholesterol-lowering.