Beta-sitosterol is one of several plant-based substances known as phytosterols. Phytosterols are similar in structure to cholesterol and may help reduce the risk of heart disease if consumed in ample quantities. The richest source sources of phytosterols are vegetable oils and the products made from them.

In addition to food sources, beta-sitosterol is sold in supplement form to treat high cholesterol and a host of other disorders. Despite its ability to lower "bad" low-density lipoprotein (LDL) cholesterol, there is only limited evidence that it can prevent or treat specific medical conditions.

Health Benefits

Alternative practitioners believe that beta-sitosterol can treat diseases as far-ranging as allergy, asthma, chronic fatigue syndrome, fibromyalgia, gallstones, migraine, psoriasis, rheumatoid arthritis, and menstrual disorders. In addition, beta-sitosterol is purported to prevent heart disease and certain forms of cancer (including prostate cancer and colon cancer).

Despite considerable gaps in clinical research, a number of smaller studies have hinted at potential benefits of beta-sitosterol use.

Cardiovascular Disease

Beta-sitosterol may reduce the risk of cardiovascular disease (CVD) by lowering LDL cholesterol in the blood.

By increasing your dietary intake, beta-sitosterol effectively competes with animal cholesterol for absorption in the intestines. Over time, this can reduce the risk of atherosclerosis (hardening of the arteries), a condition which contributes to heart attack and stroke.

Research has consistently shown that eating 2 grams of phytosterols per day can reduce your LDL cholesterol by anywhere from 8 to 10 percent.

Anything less than 2 grams per day does not confer to a reduction in CVD risk, according to 2010 guidance from the U.S. Food and Drug Administration (FDA).

Moreover, while beta-sitosterol supplements may contribute to a reduced CVD risk, there are no indications that the supplements can do so without other interventions, such as a reduced-fat diet and routine exercise.

Benign Prostatic Hyperplasia

Beta-sitosterol may aid in the treatment of an enlarged bladder, also known as benign prostatic hyperplasia or BPH.

According to a 1999 review in BJU International, beta-sitosterol was able to increase urinary output and volume in 519 men with BPH after four to 26 weeks. What the supplement was not able to do was reduce the prostate size.

Higher doses were not able to improve upon these results. While beta-sitosterol cannot directly treat BPH, it may be used in complement with traditional drugs for men with decreased urinary flow and urinary hesistancy.

Cancer

Beta-sitosterol supplements are often promoted for their anti-cancer properties. Most of the evidence supporting these claims are based on test tube studies.

According to a 2010 trial published in BMC Complementary and Alternative Medicine, beta-sitosterol isolated from tropical milkweed (Asclepias curassavica) inhibited the growth of human colon cancer cells.

Similarly, a 2003 study in Oncology Reports found that beta-sitosterol induced apoptosis in breast cancer cells. Apoptosis, a type of programmed cell death, is key to halting the spread of cancer cells.

A 2008 study published in Molecular Nutrition and Food Research found that using beta-sitosterol in combination with the breast cancer drug tamoxifen appeared to enhance the drug's effectiveness against breast cancer cells.

None of this should suggest that beta-sitosterol has any direct impact on cancer cells. Rather, it hints at a possible avenue for cancer drug development in the future.

Possible Side Effects

Beta-sitosterol is considered safe when used at the recommended doses for up to six months. Side effects may include nausea, indigestion, bloating, diarrhea, and constipation. Less commonly, beta-sitosterol has been linked to erectile dysfunction and low libido.

Beta-sitosterol should not be used in people with a rare genetic disorder known as sitosterolemia in which beta-sitosterol and other fats accumulate abnormally in the blood. Taking a beta-sitosterol supplement under such conditions may actually increase the risk of a heart attack.

Beta-sitosterol may interact with Pravachol (pravastatin) and Zetia (ezetimibe), both of which are used to lower blood cholesterol levels. Taking either these drugs can reduce the effectiveness of beta-sitosterol.

Due to the lack of safety research, beta-sitosterol should not be used in children, pregnant women, or nursing mothers. To avoid unforeseen side effects or interactions, speak with your doctor before taking a beta-sitosterol supplement.

Dosage and Preparation

There are no universal guidelines directing the appropriate use of beta-sitosterol supplements. The supplements are typically found in capsule, tablet, or soft gel form in doses ranging from 60 to 500 milligrams (mg).

Dosages of 800 mg or more per day, divided and taken before meals, have been used safely in people with high cholesterol. By contrast, a dose of no more than 130 mg per day may be enough to promote urination in men with BPH.

Widely available for purchase online, beta-sitosterol supplements are sold in many natural food shops and in stores specializing in dietary supplements.

What to Look For

Dietary supplements are largely unregulated in the United States. As a result, the contents and/or concentration of active ingredients may differ from one brand to the next. To better ensure safety and quality, opt for supplements that have been tested and certified by an independent certifying body like the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

Beta-sitosterol supplements are stable at room temperature but can degrade quickly if exposed to excessive heat or UV radiation. Always store your supplements in their original light-sensitive container, ideally in a cool, dry room.