Long-term administration of the dietary supplement saw palmetto, even at three times the usual dose, did not reduce symptoms of prostate enlargement significantly better than placebo in a large group of middle-aged men. The study from researchers at 14 institutions across the U.S. and Canada appears in the September 28 Journal of the American Medical Association and extends the results of several other double-blinded, placebo controlled trials.
"Saw palmetto extracts are commonly used by men with bothersome lower urinary tract symptoms, but our results indicate that the particular extract we tested was no better than a placebo at relieving those symptoms," says Michael Barry, MD, of the Massachusetts General Hospital Department of Medicine, lead author of the JAMA report. "It is possible that other formulations could be helpful, but a number of recent studies with negative results suggest it may be difficult to find a saw palmetto extract that is better than placebo."
Benign prostatic hyperplasia (BPH), commonly referred to as an enlarged prostate, affects around half of men at age 50 and three-quarters by age 80. The condition can be mild, but for many men symptoms such as frequent urination – including the need to visit the bathroom several times at night – difficulty urinating, and weak or intermittent urinary flow interfere with their quality of life. Several conventional medications are available to treat BPH, but their side effects can be unpleasant.
Saw palmetto extract is a common alternative treatment for BPH. Some early studies indicated that saw palmetto could reduce symptoms of BPH, but recent, more rigorous trials had less promising results. The largest previous trial, enrolling 225 men over 50, found that a standard dose of 160 mg twice a day for one year was no better than placebo at relieving symptoms. The current study was designed to see whether longer treatment with higher doses would give better results.
Conducted at 11 North American hospitals, the current trial enrolled men over 45 with moderate symptoms of BPH. Participants took daily doses of identical gelcaps that contained either saw palmetto extract or a placebo. The dosage was doubled 28 weeks into the study and then tripled at 48 weeks. Those receiving saw palmetto started at a standard daily dose of 320 mg., increased to 640 mg. and ended at 960 mg. Of the more than 300 participants who completed the study, all reached the triple dose with no significant side effects. At the end of the 72-week study period, participants receiving saw palmetto showed less improvement in a standard index of BPH symptoms than did those taking the placebo.
"The conventional medications we prescribe for BPH can have unpleasant side effects, and participants taking even the highest doses of saw palmetto had no serious adverse effects," Barry says. "So while I would tell a patient interested in trying saw palmetto that I wouldn't object, I'd make sure he understood that, on average, it doesn't seem to work any better than a placebo." Barry is a clinical professor of Medicine at Harvard Medical School
Support for the study – which was conducted by the Complementary and Alternative Medicine for Urologic Symptoms Study Group – included grants from the National Institutes of Health, including the National Center for Complementary and Alternative Medicine, and the Office of Dietary Supplements.
Celebrating the 200th anniversary of its founding in 1811, Massachusetts General Hospital (www.massgeneral.org) is the original and largest teaching hospital of Harvard Medical School. MGH conducts the largest hospital-based research program in the United States, with an annual research budget of nearly $700 million and major research centers in AIDS, cardiovascular research, cancer, computational and integrative biology, cutaneous biology, human genetics, medical imaging, neurodegenerative disorders, regenerative medicine, reproductive biology, systems biology, transplantation biology and photomedicine.