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Beta sitosterol is a type of phytochemical, classified as a sterol, that occurs naturally in many plants as a component of cellular membranes. Its chemical composition is very similar to that of cholesterol with the exception of containing one more ethyl group. In contrast to cholesterol, however, it does not contribute to the formation of arterial plaque. In fact, this substance has been shown to lower serum cholesterol levels in humans. There is also some clinical evidence to suggest that this plant sterol may have additional medicinal benefits.
In terms of the ability to reduce cholesterol levels in humans, beta sitosterol has two different effects in the body. First, it should be noted that plant sterols do promote the manufacture of cholesterol in the liver, just as animal fats do. However, this plant sterol reduces the circulation of cholesterol in the bloodstream by inhibiting its absorption in the intestines by up to 50 percent. The second part of the cholesterol-lowering process is observed in the reduced capacity for low-density lipoproteins to oxidize, which would otherwise lead to the synthesis and accumulation of LDL cholesterol, the “bad” kind.
While beta sitosterol is primarily known for its cholesterol reducing properties, it has also been studied for its antioxidant qualities. In this regard, this substance has been shown to stimulate the production of certain enzymes capable of protecting cells from oxidative damage due to free radicals. Other studies indicate that beta sitosterol may play a role in preventing the development of certain cancers, namely colon, prostate, and breast cancer. In fact, in vivo experiments have shown that this substance promotes apoptosis (death) in cancer cells, while leaving healthy cells intact. The mechanism behind this effect is believed to stem from regulating the activity of protein phosphatase A2.
Researchers have also discovered that beta sitosterol may help to reduce enlargement of the prostate, as well as improve the volume and rate of urine flow. This substance is also being studied for its potential application in managing chronic inflammatory conditions. Additional studies are focused on the immune-supporting properties of this plant sterol since initial trials have shown that it increases the production of lymphocytes and the activity of natural killer cells in humans.
Natural sources of beta sitosterol include wheat germ, rice bran, saw palmetto, avocado, and certain shrubs, such as sea buckthorn. It is also found in black cumin seeds, pumpkin seeds, flax seed, peanuts, and soybeans. Fortified dietary sources include corn oil and margarine.