Saw Palmetto for Enlarged Prostate: What the Evidence Says

Saw palmetto, extracted from berries of palm trees native to the southeastern United States, is marketed as a natural remedy for enlarged prostate (benign prostatic hyperplasia, BPH). It’s one of the top‐selling dietary supplements in the U.S., with over a third of supplement‐taking adults using it. Though folk medicine has praised its anti‐inflammatory properties for more than a century, Harvard experts urge skepticism regarding its benefits for prostate health.

Why Men Consider Saw Palmetto

BPH is common with age and impedes urinary flow, causing obstructive symptoms that worsen over time. Some propose that saw palmetto mimics 5-alpha reductase inhibitors (like finasteride) that shrink the prostate gland, but the exact mechanism remains unclear. No herbal supplement is FDA-approved to treat BPH.

What the Research Shows

  • Study 1: 225 men with moderate to severe BPH took placebo or 160 mg of saw palmetto twice daily for one year. No difference in outcomes was detected; researchers noted that the dose may have been too low.
  • Study 2: Nearly 370 men, ages 45+, received placebo or higher doses (up to 320 mg three times daily) for 18 months. Both groups reported feeling no worse or slightly better, and 40% of placebo‐treated men noted improvement, suggesting a strong placebo effect.
  • Cochrane Review (2024): Analysis of 27 placebo‐controlled trials with 4,656 participants found no improvement in urinary symptoms or quality of life from saw palmetto, alone or with other herbs, over up to 17 months.

Expert Recommendations

“Saw palmetto is unlikely to harm you, but it probably won’t provide any major benefits either,” says Dr. Heidi Rayala, urologic surgeon at Beth Israel Deaconess Medical Center and Harvard Medical School assistant professor. Dr. Michael Barry, professor of medicine at Harvard Medical School, advises men to consult a doctor first to rule out other causes of urinary obstruction, including bladder or prostate cancer.

Potential risks include interference with blood clotting, posing extra danger for men on blood thinners. Consumers should be cautious about spending on unproven alternatives.

Bottom Line

Despite its appeal as a “natural” treatment, high‐quality evidence does not support saw palmetto’s effectiveness for BPH. As Dr. Marc Garnick of Harvard Medical School warns, using it without a full medical evaluation should be discouraged. If herbal ingredients truly worked, they would likely be FDA-approved medicines covered by insurance.