The Journal of the American Medical Association has featured a randomised controlled trial that has evaluated the effect of high doses of saw palmetto extract (Serenoa repens, from saw palmetto berries) on lower urinary tract symptoms attributed to benign prostatic hyperplasia (BPH).

The double-blind, multicentre, placebo-controlled trial at 11 North American clinical sites involved 369 men aged 45 years or older, with a peak urinary flow rate of at least 4 mL/second, and an American Urological Association Symptom Index (AUASI) score of between 8 and 24 at 2 screening visits. Patients were randomised to 1, 2, and then 3 doses (320 mg/day) of saw palmetto extract or placebo, with dose increases at 24 and 48 weeks. The main outcome measure was a score between baseline and 72 weeks. Secondary outcomes included measures of urinary bother, nocturia, peak uroflow, postvoid residual volume, prostate-specific antigen level, participants' global assessments, and indices of sexual function, continence, sleep quality, and prostatitis symptoms.

The following results were reported:
• Between baseline and 72 weeks, mean AUASI scores decreased from 14.42 to 12.22 points (−2.20 points; 95% CI, −3.04 to −0.36) with saw palmetto extract and from 14.69 to 11.70 points (−2.99 points; −3.81 to −2.17) with placebo.
• Saw palmetto extract was no more effective than placebo for any secondary outcome.
• No clearly attributable adverse effects were identified.

The researchers conclude that increasing doses of a saw palmetto does not reduce lower urinary tract symptoms more than placebo in patients with BPH.