Numerous plants contain cholesterol-like compounds called sitosterols and their close relatives sitosterolins. A special mixture of these called beta-sitosterol is used for the treatment of benign prostatic hyperplasia (BPH).

What Is Beta-Sitosterol Used for Today?

Some conditions are luckier than others. For some mysterious reason, there seem to be more useful herbal treatments for BPH than almost any other disease. Beta-sitosterol joins saw palmetto, pygeum, nettle, and grass pollen as a moderately well-documented treatment for BPH.

Based on highly preliminary evidence, it has been suggested that sitosterols may also help strengthen the immune system.2 In particular, one study suggests that beta-sitosterol can help prevent the temporary immune weakness that typically occurs during recovery from endurance exercise, and can lead to a post-race infection.3

What Is the Scientific Evidence for Beta-Sitosterol?

A review of the literature, published in 1999, found a total of four double-blind placebo-controlled studies on beta-sitosterol for BPH, enrolling a total of 519 men.4-7 All but one of these studies found significant benefits in both perceived symptoms and objective measurements, such as urine flow rate.

The largest study followed 200 men with BPH for a period of 6 months.8 After the trial was completed, many of the participants were followed for an additional year, during which the benefits continued.9 Similar results were seen in a 6-month, double-blind trial of 177 individuals.10

Beta-sitosterol binds to prostate tissue and affects the metabolism of prostaglandins, substances found in the body that affect pain and inflammation.1 However, it is not clear whether this is the correct explanation for how beta-sitosterol might help in BPH.


The daily dosage of beta-sitosterol is 60 to 135 mg. Effects usually take 4 weeks to develop.

Safety Issues

Although detailed safety studies have not been performed, beta-sitosterol is believed to be safe. No significant side effects or drug interactions have been reported.11