Derived from the berries of a palm tree native to the southeastern United States, saw palmetto is a widely used dietary supplement, often promoted for prostate health. Estimates suggest that over a third of American adults who take supplements include saw palmetto in their regimen. Its history as a folk remedy stretches back more than a century, with some research pointing to anti-inflammatory properties. However, experts from Harvard Medical School advise a skeptical approach toward its purported benefits for prostate issues.
“Saw palmetto is unlikely to harm you, but it probably won’t provide any major benefits either,” says Dr. Heidi Rayala, a urologic surgeon at Harvard-affiliated Beth Israel Deaconess Medical Center and an assistant professor of urology at Harvard Medical School. This cautious perspective is rooted in a thorough examination of the scientific evidence, which raises questions about the supplement’s effectiveness for conditions like benign prostatic hyperplasia (BPH).
BPH, or an enlarged prostate, is a common age-related condition in men that can obstruct urinary flow and lead to worsening symptoms over time. The mechanism by which saw palmetto might alleviate these symptoms remains unclear, though some evidence suggests it could mimic the effects of certain prescription drugs, such as 5-alpha reductase inhibitors like finasteride (Proscar), which work by shrinking the prostate gland. Despite this, no herbal supplement, including saw palmetto, has received approval in the United States as a treatment for BPH.
The American Urological Association highlights significant flaws in studies supporting saw palmetto for enlarged prostates, including short durations and a lack of placebo controls. Much of the supporting evidence comes from small-scale research funded by companies that sell dietary supplements, which can introduce bias. This underscores the importance of relying on high-quality, independent clinical trials to assess true efficacy.
Randomized clinical trials, considered the gold standard in research, have generally shown no benefits from saw palmetto for BPH. In one study, 225 men with moderate to severe BPH were given either a placebo or 160 milligrams of saw palmetto twice daily for a year. Researchers found no difference in outcomes, though they noted that the doses tested might have been too low to produce measurable effects.
A larger follow-up study tested higher doses, up to 320 milligrams taken three times a day, in nearly 370 men aged 45 and older. After a year and a half, participants in both the treatment and placebo groups reported feeling either no worse or slightly better. Notably, 40% of those on the placebo said their symptoms had improved, suggesting that the perceived benefits could be linked to the placebo effect—the simple act of taking a pill.
Dr. Michael Barry, a professor of medicine at Harvard Medical School who led the study, emphasizes the importance of consulting a doctor before trying saw palmetto. This step is crucial to rule out other potential causes of urinary obstruction, such as bladder or prostate cancer. Additionally, saw palmetto may interfere with blood clotting, posing risks for men who take blood thinners.
The most recent comprehensive analysis comes from a Cochrane Review of 27 placebo-controlled studies involving a total of 4,656 participants. Published in 2024, the results showed no improvement in urinary symptoms or quality of life from taking saw palmetto, either alone or combined with other herbal supplements, over periods of up to 17 months.
Dr. Rayala offers a practical perspective: “If the ingredients in these herbal products worked well for urinary symptoms, drug companies would have already had them approved by the FDA as a medicine that insurance companies would have to cover. It’s okay to take them, but just be cautious about spending too much of your own money on these alternatives.”
Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of the Harvard Medical School Guide to Prostate Diseases, adds, “It is easy to understand why so many find taking a naturally occurring supplement for treating urinary difficulties in middle age appealing. However, evidence of effectiveness with saw palmetto is lacking, and its use for BPH and other common urinary symptoms without a full evaluation of the potential cause should be discouraged.”
In summary, while saw palmetto is a popular supplement with a long history of use, current scientific evidence does not support its effectiveness for treating an enlarged prostate or improving urinary symptoms. Men considering this option should prioritize medical consultation to ensure safe and informed decisions about their health.
