Saw Palmetto and Prostate Health: What the Evidence Shows

Saw palmetto is a top-selling dietary supplement marketed as a natural remedy for an enlarged prostate. Extracted from berries of the saw palmetto palm—native to the southeastern United States—over a third of U.S. adults taking supplements use it. Some evidence suggests anti-inflammatory properties, and folk medicine has used it for over a century. However, Harvard experts advise skepticism about its prostate benefits.

Understanding Benign Prostatic Hyperplasia (BPH)

BPH is a common age-related enlargement of the prostate gland that impedes urinary flow, causing obstructive symptoms that often worsen over time. No herbal supplement, including saw palmetto, is FDA-approved for BPH treatment.

Proposed Mechanism of Action

Some research suggests saw palmetto may mimic 5-alpha reductase inhibitors (e.g., finasteride), which shrink the prostate. The exact way saw palmetto might improve urinary symptoms remains unclear.

Key Research Findings

  1. Small, Year-Long Study: 225 men with moderate to severe BPH received either placebo or 160 mg saw palmetto twice daily. No difference in outcomes was detected, though investigators noted the dose might have been too low.
  2. Larger, 18-Month Study: Nearly 370 men aged 45+ were randomized to placebo or up to 320 mg saw palmetto three times daily. After 18 months, both groups reported similar symptom changes; notably, 40% of placebo-treated men reported improvement.
  3. 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 in combination with other herbs) over periods up to 17 months.

Expert Recommendations and Cautions

  • Consult a physician before trying saw palmetto to rule out other causes of urinary obstruction, such as bladder or prostate cancer.
  • Saw palmetto may interfere with blood clotting and pose risks for men on blood thinners.
  • “Saw palmetto is unlikely to harm you, but it probably won’t provide any major benefits,” says Dr. Heidi Rayala of Harvard Medical School.
  • Dr. Marc Garnick advises against using saw palmetto for BPH symptoms without a full evaluation, noting the lack of evidence for effectiveness.
  • Be cautious about spending money on supplements lacking proven benefits; FDA-approved medications remain the standard for BPH treatment.