Millions of older American men use saw palmetto to treat an enlarged prostate, clinically known as benign prostatic hyperplasia (BPH), but a new study concludes that this herbal supplement is ineffective.
Several smaller studies had suggested that the extract might be of limited benefit, but this controlled, blinded study found that, "over a 12- month period, saw palmetto was no better than placebo in changing symptoms for this condition," according to lead researcher Dr. Stephen Bent, an assistant professor of medicine at the University of California, San Francisco.
In the trial, researchers tracked the symptoms of 225 men over th e age of 49 who had moderate to severe BPH. Half of the men took 160 milligrams (mg) of saw palmetto twice daily, while the other half took a placebo.
After one year, the researchers found no difference between the two groups in terms of symptoms, urine flow rates, prostate size, quality of life or blood levels of prostate-specific antigen (PSA), a marker for an enlarged prostate.
"Obviously, for anyone who holds saw palmetto in high regard, these results are a little bit disappointing," says Dr. Ronald A. Morton, director of urologic oncology at the Cancer Institute of New Jersey.
Bent notes that the research on the efficacy of saw palmetto for BPH has been ambiguous, with some studies suggesting a benefit and others finding it to be of no help at all.
"Those studies were of short duration, however, or they didn't use what is now the measure of symptoms," Bent says. Also, these prior studies were not always blinded, meaning the participants might have known if they were taking a placebo, which could bias the results.
Bent's team sought to address many of these issues, taking special care to ensure proper blinding and using a larger group of patients so the results would be statistically significant.
This research is "the most thorough and well controlled study of the effect of saw palmetto on men with BPH that's ever been done," according to Morton.
The researchers also went to great lengths to choose a top-notch product-in this case, a brand of saw palmetto capsules marketed in the United States by Rexall-Sundown Co. "We had an external advisory committee from the National Center for Complementary and Alternative Medicine-experts in the field-who evaluated a number of different extracts," Bent says. "They felt this was the best one."
In a statement, Andrew Shao, vice president of the Council for Responsible Nutrition, a supplements industry trade group, calls the findings "puzzling, given that more than 20 studies have shown promising findings for saw palmetto in alleviating symptoms commonly associated with prostate problems."
Morton agrees. "There are millions and millions of men out there who take saw palmetto. And if you review the literature on saw palmetto, it's really all over the map," he says.
Shao admits that this study was well-designed, but speculates that the negative findings could be due to the study's focus on patients who had moderate to severe BPH. According to Shao, the bulk of the positive literature on saw palmetto involved men who had milder symptoms.
"The exclusion of those patients with mild symptoms may have reduced [the study's] ability to detect the benefits we've seen in other trials," he says.
What To Do
Because there's no evidence that saw palmetto poses any long-term safety risk, "if people are taking this and feel like they are getting some benefit, I think it's worth continuing," Bent advises.
Morton agrees that saw palmetto is probably safe, but he questions whether too many men plagued by BPH are using this ineffective remedy in lieu of conventional drugs whose efficacy is supported by clinical research.
"There are two medications that we commonly use for men with BPH," says Morton. "One includes drugs called alpha blockers, and the other group is 5-alpha-red,uctase inhibitors. Alpha blockers cause a relaxation of the prostate that makes it easier for a man to urinate. And 5- alpha-reductase inhibitors shrink the prostate."
Either of these medications may be more effective than over-the-counter saw palmetto.