The fruit of the saw palmetto tree does not relieve symptoms of an enlarged prostate, even when men take the herbal supplement in very high doses, a new study shows.
The research is published Sept. 28, 2011, in the Journal of the American Medical Association.
Many older U.S. men take saw palmetto extract in an attempt to reduce bothersome symptoms of a swollen prostate, including frequent urination and a sense of urgency. Its use in Europe is even more widespread because doctors often recommend saw palmetto over more traditional drug treatments.
Results of the new study may settle an ongoing debate over the effectiveness of saw palmetto for a condition known as benign prostatic hyperplasia (BPH). Earlier studies of the supplement have produced conflicting results, and none have evaluated the benefits of saw palmetto in high doses.
In the current study, however, men took up to three times the standard dose of saw palmetto.
"Now we know that even very high doses of saw palmetto make absolutely no difference," says co-author Gerald Andriole, MD, the Robert K. Royce Distinguished Professor and chief of urologic surgery at Washington University School of Medicine in St. Louis. "Men should not spend their money on this herbal supplement as a way to reduce symptoms of enlarged prostate because it clearly does not work any better than a sugar pill."
The multi-center study, led by Michael Barry, MD, at Massachusetts General Hospital in Boston, involved more than 300 men ages 45 and older who had moderate symptoms suggestive of an enlarged prostate, such as frequent urination, difficulty emptying their bladders and a weak urine stream. The men were randomly selected to receive a daily dose of saw palmetto extract, beginning at 320 milligrams, or an identical-looking placebo pill with the same distinctive smell and taste.
After 24 weeks, the saw palmetto dosage was increased to 640 milligrams a day, and after another 24 weeks, to 960 milligrams a day -- triple the standard dose. In all, men took saw palmetto or a placebo for nearly 17 months. Neither the physicians nor the patients knew who was taking what regimen until the end of the study.
The researchers found that among men who took saw palmetto, prostate problems improved slightly but not more than in men taking a placebo.
"We commonly see this in clinical trials," Andriole explains. "Patients often report an improvement in symptoms because they are taking something, even if it is a placebo. But in this study, there was no benefit to taking saw palmetto over the placebo."
The researchers found that saw palmetto had no greater effect than the placebo on BPH symptoms as well as other conditions related to an enlarged prostate such as waking at night to urinate, PSA level and bladder control.
About half of all men over age 50 have BPH, which becomes more common as men age. If urination becomes difficult or painful, Andriole advises men to visit their physician. Several approved medications, such as alpha-blockers and 5-alpha reductase inhibitors, are available to successfully treat the condition.
The research was funded by the National Institutes of Health (NIH); the National Institute of Diabetes and Digestive and Kidney Diseases; the National Center for Complementary and Alternative Medicine; and the NIH Office of Dietary Supplements. Saw palmetto fruit extract and matching placebo were donated by Rottapharm/Madaus, Cologne, Germany.
The study was conducted under an Investigational New Drug Application from the U.S. Food and Drug Administration.
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