Saw palmetto is sold as a natural treatment for an enlarged prostate. It comes from berries that grow on saw palmetto palm trees in the southeastern United States.
Over a third of U.S. adults who take supplements use saw palmetto. Some studies suggest it may help reduce inflammation, and people have used it as folk medicine for more than 100 years.
Harvard experts advise caution. “Saw palmetto is unlikely to harm you, but it probably won’t provide any big benefits,” says Dr. Heidi Rayala, assistant professor of urology at Harvard Medical School.
BPH and how saw palmetto might work
As men get older, the prostate often grows larger. This is called benign prostatic hyperplasia (BPH). A bigger prostate can press on the tube that carries urine, making it hard to pee.
It’s not clear exactly how saw palmetto would help the prostate. Some think it might block the same enzyme as certain BPH drugs that shrink the gland. No herbal supplement is approved to treat BPH. The American Urological Association notes that many studies of saw palmetto are short, small, or funded by supplement makers.
What do clinical trials show?
The best studies find no real benefit for BPH. In one trial, 225 men with moderate to severe BPH took either a fake pill or 160 mg of saw palmetto twice daily for a year. Both groups had the same outcomes—no clear improvement.
Another larger trial gave nearly 370 men up to 320 mg of saw palmetto three times a day or a placebo for 18 months. Men in both groups said they felt the same or slightly better. Surprisingly, 40% of those on the placebo reported feeling better, showing how strong the placebo effect can be.
Dr. Michael Barry of Harvard Medical School led this research. He recommends talking with a doctor first to rule out other causes of urinary problems, such as prostate or bladder cancer. He also warns that saw palmetto may affect blood clotting, which can be risky for men on blood thinners.
Recent findings
A recent review of 27 studies involving 4,656 men found no improvement in urinary symptoms or quality of life with saw palmetto, even after 17 months.
“If these herbs really worked, drug makers would have them approved as medicine,” says Dr. Rayala. “It’s okay to try them, but don’t spend too much money.”
Dr. Marc Garnick of Harvard Medical School adds, “It’s easy to see why people want a natural option for middle-age urinary troubles. But proof that saw palmetto works is missing. Men should get a full medical check before using it.”