Conflicting studies on saw palmetto's effect on prostate

Extract of saw palmetto, the Serenoa repens plant, has long been promoted as a way to prevent the prostate from growing large.

"There are studies that show it works and there are studies that show it doesn't work. And if you look at it very, very closely, the studies where it doesn't work are the good studies -- randomized, multi-center, controlled studies," says Dr. Claus Roehrborn, a urologist at the University of Texas Southwestern Medical Center in Dallas. "My take on it is, it ain't working."

A 2002 review of saw palmetto studies published in the Cochrane Database of Systematic Reviews found moderate effects of saw palmetto on symptoms and urine-flow measures. Yet the review was critical of the methodologies used in the studies: Of the 21 included in the review, only 13 compared the effects of saw palmetto with a placebo group, and only one used a symptom scale in line with internationally accepted standards. Studies were generally done on a small number of subjects and lasted 13 weeks on average.

A large study published in the New England Journal of Medicine in 2006 gave 225 men either saw palmetto or a placebo for a year and found no effect on self-reports of urinary symptoms or quality of life or on objective measures such as prostate size or urine-flow rate.

It's possible that higher doses of the extract may provide better or more consistent results, says Dr. Kevin McVary, a urologist at Northwestern University Feinberg School of Medicine in Chicago. McVary is working on a National Institutes of Health-funded study to address that unknown.

-- Jill U. Adams