While several small studies suggest that saw palmetto may be effective for treating benign prostatic hyperplasia (BPH) symptoms, most larger trials found little or no evidence that saw palmetto affects prostate disease. In 2006, a large study of 225 men with moderate-to-severe BPH found no improvement with 320 milligrams of saw palmetto daily for 1 year versus placebo. The National Center for Complementary and Integrative Health (NCCIH) co-funded the study with the National Institute of Diabetes and Digestive and Kidney Diseases.
Saw palmetto does not appear to affect readings of prostate-specific antigen (PSA) levels. PSA is protein produced by cells in the prostate. The PSA test is used to screen for prostate cancer and to monitor patients who have had prostate cancer.