Saw palmetto extract likely won't relieve enlarged prostate symptoms

Sep 25, 2011
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More than 2 million American men have turned to saw palmetto extract to help alleviate the uncomfortable symptoms of having an enlarged prostate. It remains a popular herbal remedy despite the fact that a spate of clinical trials in the past 10 years have found its benefits to be limited at best. That may change once men learn about the results of a new trial published in Wednesday’s edition of the Journal of the American Medical Assn.

First, a primer on enlarged prostates. According to the National Kidney & Urologic Diseases Information Clearinghouse at the National Institutes of Health, a man’s prostate enters a growing phase around age 25 and never stops. Eventually, the prostate gets big enough to encroach on the urethra, squeezing it until it’s blocked “like a clamp on a garden hose.” This irritates the bladder, causing men to make frequent trips to the bathroom and eventually resulting in a bladder that doesn’t empty itself completely. The NIH says that more than half of men in their 60s and up to 90% of men who reach their 70s suffer symptoms of an enlarged prostate, known formally as benign prostatic hyperplasia or BPH.

Understandably, men would want to do something about this. There have been suggestions that saw palmetto extract has anti-inflammatory and anti-androgenic effects that could help. A 2002 review study found that the extract improved urine flow and reduced the urge to wake up in the middle of the night to relieve oneself.

In subsequent trials, these benefits have weakened. The largest such study included 225 men and found that those who took 320 milligrams of the extract each day were no better off after one year than men who took a placebo. It was published in the New England Journal of Medicine in 2009.

The new study in JAMA included 369 men whose average age was 61. About half of them were given saw palmetto extract gelcaps and the rest got identical pills with no active ingredient (neither study volunteers nor their doctors knew who had the real pills and who had the placebos). As in the prior studies, the men started out taking 320 milligrams of the extract per day. Then, at 24 weeks, they doubled the dose to 640 mg per day and at 48 weeks it jumped again to 960 mg per day. The trial ended after 72 weeks.

By the time the study was over, the men who had taken the extract saw their American Urological Assn. Symptom Index (AUASI) score fall by an average of 2.20 points. Sounds good, except that the group taking the placebo saw their average score drop by 2.99 points. Looked at another way, the researchers reported that 42.6% of the men in the extract group saw their AUASI scores fall by at least three points; 44.2% of the men in the placebo group saw the same degree of benefit.

The story held true for all dose levels, even the highest ones. No matter how they sliced it, “saw palmetto extract was no better than placebo,” the researchers wrote. “A recent series of negative trials using different saw palmetto extract preparations makes it increasingly unlikely a dose of some preparation will be identified that is better than placebo.”

The study was funded by several offices within the NIH, including the National Center for Complementary and Alternative Medicine. The gelcaps were provided by Rottapharm/Madaus, a supplement maker in Germany.

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