WASHINGTON — Saw palmetto, a widely used herbal dietary supplement, does not reduce urinary problems associated with prostate enlargement any better than a placebo, according to research funded by the National Institutes of Health.
Prostate enlargement, also called benign prostatic hyperplasia, can cause frequent urination, a weak or intermittent urine stream and an inability to empty the bladder completely. More than half of men in their 60s, and up to 90 percent in their 70s and 80s, have symptoms of BPH.
The National Institute of Diabetes and Digestive and Kidney Diseases, the National Center for Complementary and Alternative Medicine and the Office of Dietary Supplements supported the study. All are part of the NIH.
According to Robert A. Star, M.D., director of the NIDDK’s Division of Kidney, Urologic and Hematologic Diseases, the current study met an important need for rigorous evaluation of standard and higher doses of saw palmetto.
The trial also confirmed results of the earlier NIDDK- and NCCAM-sponsored Saw Palmetto Trial for Enlarged Prostates, which found that a standard daily dose of 320 milligrams provided no greater symptom relief than placebo.
“Investigators designed the current trial to determine whether daily doses of up to 960 milligrams — three times the standard daily dose — would prove better than a placebo at improving lower urinary tract symptoms in men due to BPH,” said Star.
“We were disappointed to find that higher doses of saw palmetto did not improve symptoms more than placebo.”
Josephine P. Briggs, M.D., director of NCCAM, added that this study further illustrates the importance of conducting research on botanical products that are used extensively by the general public.
“This was a well-designed study that addressed limitations of earlier, smaller trials — it was a multicenter study with a larger sample size and tested different doses of a carefully analyzed saw palmetto product,” Briggs said.
According to Joseph M. Betz, Ph.D., director of the Analytical Methods and Reference Materials program at ODS and a study co-author, the study used a very well-characterized saw palmetto product.
Through batch testing, study investigators took extreme care to ensure the composition of the supplement was consistent over the whole study.
“Saw palmetto and other herbs are often manufactured in different ways, so no two brands are likely to have the same composition,” Betz said.
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