Does it work?


Can saw palmetto act as a remedy to benign prostatic hyperplasia?

BACKGROUND: Benign prostatic hyperplasia (BPH) is a common condition among older men. Nearly 20 per cent of men in their 50s are affected by BPH; among men in their 70s, about 35 per cent have significant problems with BPH, although many have some degree of symptoms.

The exact cause of BPH is not known, but the prostate gland enlarges and causes what are called lower urinary tract symptoms (LUTS). The most common examples are frequent desire to urinate (especially during the night), difficulty urinating and weak flow. The symptoms range from being irritating or embarrassing, to those that are very painful and can lead to serious problems.

BPH is commonly treated with herbal remedies because the available conventional treatments have limitations and side effects.

The herb most commonly used for BPH is saw palmetto, also known as the American dwarf palm tree or Serenoa repens. The ripe fruit is used to make the herbal remedy by extracting fatty acids and oils using water insoluble solvents. Products are usually standardised to contain 80 to 90 per cent fatty acids.


Earlier research found evidence that saw palmetto gave mild to moderate improvements when examined for a 2002 Cochrane Collaboration systematic review. These reviews are available free of charge online in Ireland due to funding from the Health Research Board (

Cochrane reviews are updated every few years, and the 2010 version on saw palmetto came to a different conclusion. The evidence no longer shows that saw palmetto is any more effective in reducing urinary symptoms than a placebo.

This change has occurred because earlier studies were of short duration and had few participants. The latest Cochrane review included the results of the largest placebo-controlled trial to date called the Saw Palmetto Treatment of Enlarged Prostates (STEP) study.

Funded by the US National Institutes of Health, the STEP study involved more than 200 men taking saw palmetto for one year. No significant differences in urinary symptoms were found between those taking saw palmetto or a placebo.

The STEP study used one product where men took 320mg daily. Funding for a much larger trial was obtained in which three different doses of saw palmetto are being tested. This study involves 3,300 men and is called the CAMUS trial. Its results should provide even clearer evidence about the effectiveness of saw palmetto.


While the STEP study found that saw palmetto was not effective for LUTS, it also found no evidence of significant adverse effects. The number and type of adverse effects were practically the same in the saw palmetto and placebo groups.

Another large review of all reports of saw palmetto adverse effects found no clear evidence of problems. The most commonly reported side effects are abdominal pain, diarrhoea, fatigue and headache.

The on-going CAMUS study includes a comprehensive assessment of adverse effects and should provide important additional information.

Self-medication can be a problem if people with serious illnesses avoid medical care. BPH is not prostate cancer, but men with prostate cancer can have some of the same symptoms. Saw palmetto does not affect pancreatic cancer. Large population studies found that men taking saw palmetto had the same risk of developing prostate cancer as those not taking it. Saw palmetto does not help prevent or treat prostate cancer.


In recent years, larger and better studies have found that saw palmetto is not effective in relieving BPH and its lower urinary tract symptoms.

Pharmaceuticals called alpha blockers can effectively relieve LUTS and reduce enlarged prostate glands, but they have problematic side effects.

Men looking for an alternative will have to await the results of the CAMUS trial, which might show if certain doses have benefits for certain symptoms. For now, it appears that benefits experienced from saw palmetto are most likely due to the placebo effect.

Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University