NIH Study Raises Doubt over Saw Palmetto for Male Urinary Health

At three times the standard dosage, supplementing with saw palmetto(Serenoa repens) may be no more effective than placebo for improving urinary health, says a new NIH study.

Saw palmetto is widely regarded for natural support of male urinary health, including support for benign prostate enlargement. Yet recent trials on the ingredient and prostate improvement have yielded unsatisfactory results, including a 2009 Cochrane review and the 2006 Saw Palmetto Treatment for Enlarged Prostates (STEP) study, considered the largest related trial at its time.

A new JAMA study, funded by the NIH and performed at 11 clinical sites, assessed the effect of saw palmetto extract on benign prostate enlargement markers in 369 men age 45 or older. Men were assigned to 320 mg/day of saw palmetto extract (recognized as a standard dosage) or a matching placebo for 72 weeks. The dosage was increased to two and three dosages at 24 and 48 weeks respectively.

Peak urinary flow and American Urological Association Symptom Index (AUASI) scores were assessed at baseline and each time of increased dosage.

From baseline to 72 weeks, mean AUASI scores decreased from 14.42 points to 12.22 points with saw palmetto and 14.69 points to 11.70 points with placebo. Changes in peak urinary flow rate were also not different across treatments; thus, saw palmetto extract was deemed no more effective than placebo in reducing lower urinary prostate symptoms.

While the results of this most-recent trial do not support saw palmetto for significant improvement of male urinary health, the Council for Responsible Nutrition (CRN; Washington, DC) cited potential weaknesses of the JAMA study and historical evidence of a beneficial effect with saw palmetto.

“In this study, both the placebo group and the treatment group saw improvements in their symptoms, creating some limitations for interpreting results,” said CRN vice president of scientific and regulatory affairs Duffy MacKay, ND. “Although there is no clear explanation as to why the placebo group showed some improvement without intervention, it is possible that both groups may have included men whose urinary tract symptoms were not actually related to an enlarged prostate. Further, the trial might not have been large enough or long enough to have found a statistically significant benefit in the treatment group.”

Saw palmetto extract and matching placebo were provided by Rottapharm/Madaus (Cologne, Germany).