Oakland, Calif. February 8, 2006 - The herbal remedy saw palmetto is no more effective than a placebo at treating symptoms related to enlargement of the prostate gland, according to a new study in the Feb. 9th issue of the New England Journal of Medicine.
"The results are disappointing, particularly for the estimated two million American men who take saw palmetto," said Andy Avins MD, MPH of the Kaiser Permanente Division of Research in Oakland, Calif. and co-leader of the study.
In Benign Prostatic Hyperplasia (BPH) the prostate gland enlarges, causing an obstruction that can impair urinary function. Saw palmetto is commonly used as an alternative to prescription medications approved by the Food and Drug Administration for the condition. The National Institutes of Health says BPH affects more than 50 percent of men 60 and older, and more than 90 percent of men 70 and older.
The year-long, double-blind study, by researchers at Kaiser Permanente and UCSF/San Francisco VA Medical Center, followed 225 men diagnosed with BPH. The patients were randomly assigned to take either 160mg of saw palmetto (the amount used in the vast majority of prior clinical trials) or a placebo twice a day for one year. The researchers say there was no statistically significant difference between the two groups in terms of symptom changes either during the trial, or at the end of the year. "
Obviously this is not encouraging news for men who are considering taking saw palmetto to treat their BPH," said Avins. "Not only did it show no overall benefit, but it also showed no benefit when we looked at it in subgroups of patients who had different levels of severity of symptoms, or who had different sizes of prostate. On the other hand, we also found no evidence of toxicity attributable to saw palmetto, at least over the year-long study period."
The study findings contradict several previous studies which suggested the herb was an effective treatment for BPH. The researchers say there are several possible explanations for this.
Previous studies were smaller in size and duration. In measuring the severity of BPH most of those studies did not apply the same method that is commonly used to measure the effectiveness of prescription medications for the problem.
Another potential problem with earlier studies has to do with the nature of saw palmetto itself, according to Stephen Bent, MD, staff physician at the VA Medical Center and co-author of the study. "This is a very pungent herb, and it took our research team a long time to create a placebo that convincingly duplicates its strong smell and taste. We suspect that prior trials didn't adequately address that problem." Bent said.
He added: "It's possible that some of the positive findings in earlier work may be due to the fact that the blinding wasn't adequate. Someone who's taking something that's smelly and likely to be the plant extract is perhaps more likely to report a benefit than someone who's taking an odorless and tasteless tablet."
The researchers say this may not be the final word on the subject. They say it is possible saw palmetto may be effective at higher doses. "The NIH is continuing to investigate the potential value of saw palmetto and other plant-based therapies for BPH," said Avins, "and further studies are being planned."
Co-authors of the study include: Christopher Kane, MD, and Katsuto Shinohara, MD of the SFVA Medical Center; John Neuhaus, PhD and Esther S. Hudes, PhD, MPH of UCSF; and Harley Goldberg, DO, of KPNC and UCSF.
The study was funded by a grant from the NIH that was administered by the Northern California Institute for Research and Education.