Beta-sitosterol is the most abundant phytosterol in the diet. It is also widely distributed in the plant kingdom and found in such botanicals as Serenoa repens (saw palmetto), Curcurbita pepo (pumpkin seed) and Pygeum africanum. These three botanicals are used in the herbal management of benign prostatic hypertrophy (BPH). There is some belief that beta-sitosterol plays some role in the possible benefits of these herbs in BPH. Beta-sitosterol itself is used as a medicine in Europe for BPH.
Chemically, beta-sitosterol is a very close relative of cholesterol. It differs from cholesterol by the presence of an ethyl group at the 24th carbon position of the side chain. It is also known as (3beta)-stigmast-5-en-3-ol; 22:23-dihydrostigmasterol; alpha-dihydrofucosterol; delta 5-stigmasten- 3beta-ol; 24beta-ethyl-delta 5-cholesten-3beta-ol; alpha-phytosterol; cinchol; cupreol; rhamnol; quebrachol; and sitosterin. Beta-sitosterol is extremely insoluble in aqueous media and poorly soluble in lipid media. It is found in nature in ester and glycoside forms, both of which forms are more soluble than beta-sitosterol itself.
Beta-sitosterol is one of hundreds of plant-derived "sterol" compounds (including sterols and sterolins) that have structural similarity to the cholesterol made in our bodies. The most prevalent phytosterols in the diet are beta-sitosterol, campesterol and stigmasterol. Plant oils contain the highest concentration of phytosterols - so nuts and seeds contain fairly high levels and all fruits and vegetables generally contain some amount of phytosterols. Perhaps the best way to obtain beta-sitosterol is to eat a diet rich in fruits, vegetables, nuts and seeds (which obviously brings numerous other benefits as well).
Beta-sitosterol has good evidence of effectiveness in treating BPH - but not quite as good as other supplements such as Saw palmetto and Pygeum. As a cholesterol-lowering supplement, again, the evidence for beta-sitosterol is good, but not quite as strong as either red yeast rice (no longer available as a supplement) or policosanol. As an immune-enhancer, echinacea has much more evidence of effectiveness, but beta-sitosterol appears to be quite beneficial in maintaining immune function during periods of heightened stress (such as exercise recovery). As a cancer-preventive agent, the animal and test-tube data for beta-sitosterol is certainly tantalizing, but preliminary, and needs further substantiation in humans.
Beta-sitosterol has been known to reduce cholesterol levels over the last three decades. Its close chemical resemblance to cholesterol enables it to block the absorption of cholesterol by competitive inhibition. Although beta-sitosterol is not well absorbed by the body (5-10%), when consumed with cholesterol it effectively blocks cholesterol's absorption, resulting in lower serum cholesterol levels. Beta-sitosterol has also been shown to improve lipoprotein (HDL, LDL) profiles. Plant sterols actually improved prostate symptom scores and reduced urine volume and residual urine levels without reducing the size of the prostate. Beta-sitosterol was one of the major components in these herbal preparations. Researchers also cited that beta-sitosterol alone was an effective option in the treatment of BPH. Beta-sitosterol acts against cancer. It is found to reduce the growth of human prostate and colon cancer cells. It also acts against lymphocytic leukemia. It appears that diets high in vegetables and fruits prevent cancer to a certain degree. Soybeans are superb sources of protein that reduces the risk of cancer too. Beta-sitosterol is one of the key compounds in soybeans that suppress carcinogenosis. Beta-sitosterol may give a boost to competitive athletes who often suffer from immune suppression and reduced inflammatory response during their intense training periods and competitions. Beta-sitosterol had been shown not only to boost their immunity but also noted to enhance lymphocyte proliferation and NK-cell activity. This is particularly useful to people who are physically stressed, medically unwell or recovering from illness. Beta-sitosterol has been shown to normalize blood sugar and insulin levels in Type II diabetics by stimulating the release of insulin in the presence of non-stimulatory glucose concentrations, and inhibiting glucose-6-phosphatase. In the liver, the enzyme glucose-6-phosphatase is the primary pathway for conversion of dietary carbohydrates to blood sugar. Glucose-6-phosphatase dephosphorylates glucose-6-phosphate to yield free D-glucose. Free D-glucose passes into the blood, thus elevating blood sugar levels. Reducing the blood glucose levels by down-regulation of glucose-6-phosphatase helps delay diabetes caused by old age.