Saw Palmetto—Does it Work?

A large study of saw palmetto (Serenoa repens) has found no benefit for men with benign prostate enlargement (New England Journal of Medicine 2006;354:557–66), but while the study is the most rigorously controlled to date, it raises some questions since the results are inconsistent with other research.

In this double-blind trial, 225 men over age 49 who had moderate to severe symptoms of benign prostatic hyperplasia (BPH) were randomly assigned to one year of treatment with a proprietary saw palmetto extract (160 mg twice a day) or a placebo. Researchers tracked symptoms (such as urinary frequency, especially at night), urinary flow rate, changes in prostate size, residual urinary volume after voiding, quality of life, laboratory values, and side effects. They found no significant difference between the saw palmetto and placebo groups for any of these outcomes during the year, though no negative effects were seen.

In contrast to the present findings, previous studies of saw palmetto have found it to be effective for mild to moderate BPH. A 1998 review of clinical trials of saw palmetto in the Journal of the American Medical Association found that the herb improved BPH symptoms and urinary flow, providing benefits similar to those of finasteride (Proscar; the most commonly prescribed drug for BPH), but with fewer side effects. These studies were smaller, not as long, and some had design flaws, but the benefits of taking saw palmetto for BPH has been well-enough demonstrated for it to be recommended as a first-line treatment by many urologists.

What explains the discrepancy between the results of the current study and those of previous studies? The authors had several theories: previous studies did not effectively mask the identity of the active and placebo formulations; the level of active ingredient in the extract was possibly too low to produce a measurable effect; and the severity of the condition in some of the participants in this study may have made them less likely to have a positive response. It is interesting to note that the present study excluded men with mild BPH, even though previous studies have found the herb effective for mild to moderate BPH.

So what’s a man with an enlarged prostate to do? If the condition is mild to moderate, many studies suggest that he will benefit by taking saw palmetto.

Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.

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