After 72 weeks of treatment, 42.6 percent of the men receiving saw palmetto extract had a 2.2 improvement in scores on the American Urological Association Symptom Index, while about 44 percent of men taking placebo showed about a 3-point improvement in their score, the researchers found.
Overall, there was a difference in the scores of 0.79 points in favor of the placebo, they added.
Even at the highest dose -- 960 milligrams -- saw palmetto fared no better than placebo. Also, saw palmetto extract was no better than placebo for any of the other outcomes, including measures of urinary bother, excessive urination at night, measures of sexual function, continence, sleep quality and symptoms of prostatitis (inflammation of the prostate).
"We've always known there's a pretty big placebo effect with lower urinary tract symptoms," Barry said.
There are different ways to extract chemicals from saw palmetto berries, and it's possible that another method -- or another extract -- might work, Barry said. "But, given the series of well-done negative studies, it's harder to think that someone will be able to find an extract that will work," he added.
Dr. Stephen Bent, an assistant professor of medicine at the University of California, San Francisco, who has done his own research on BPH and saw palmetto extract, said the study results didn't surprise him.
The findings from this study are "definitively negative," he said.
"When men try saw palmetto, chances are they are going to have some improvement, because they are going to experience a placebo effect," Bent said. "It may be that men get a benefit when they take a saw palmetto product, but it has nothing to do with saw palmetto."
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