Even at doses three times higher than usual, saw palmetto extract was no better than placebo at improving lower urinary tract symptoms attributed to benign prostatic hyperplasia in a study in the Sept. 28 issue of JAMA.
Extracts from the fruit of the saw palmetto dwarf palm tree are the most widely used plant extracts in the United States and Europe for urinary symptoms. They are purported to have anti-androgenic, anti-inflammatory, and antiproliferative effects, but none of these properties have been proved.
A meta-analysis from approximately 10 years ago showed that, compared with placebo, saw palmetto significantly reduced nocturia and improved peak uroflow, as well as being rated by study subjects as more beneficial. But more recent clinical trials and reviews of the literature have had more negative findings.
"We conducted a randomized clinical trial to determine if a standard daily dose of saw palmetto extract increased to a double and then a triple daily dose over 72 weeks would improve lower urinary tract symptoms attributed to benign prostatic hypertrophy," said Dr. Michael J. Barry of Massachusetts General Hospital, Boston, and his associates in the Complementary and Alternative Medicine for Urological Symptoms (CAMUS) study group.
This study design allowed an adequate duration of treatment – 24 weeks at each dose level – to assess outcomes, they noted.
The double-blind trial included 369 men aged 45 years and older who had a peak uroflow rate of at least 4 mL per second and a score of 8-24 on the American Urological Association Symptom Index (AUASI) at baseline. They were treated at 11 sites across North America with a standard dose (320 mg/day) of gelcaps containing saw palmetto extract or placebo, which was escalated to 640 mg/day at 24 weeks and 960 mg/day at 48 weeks.
The primary outcome measure was the change in AUASI score at 72 weeks. This decreased only slightly, and to nearly the same degree, in both groups: The reduction was 2.20 points with saw palmetto and 2.99 points with placebo, the investigators said (JAMA 2011;306:1344-51).
The result was the same in a per-protocol analysis of the 151 subjects who received saw palmetto and the 155 who received placebo for the entire duration of the study.
Similarly, the proportion of men who achieved a minimal (3-point) decrease in AUASI score over time was 42.6% with saw palmetto and 44.2% with placebo, slightly favoring placebo. A dose-response analysis showed that saw palmetto was no better than placebo at any dose level.
Further analyses also showed that the active treatment was no better than placebo for a wide range of secondary outcomes including change in BPH Index scores and change in measures of nocturia, peak uroflow, postvoiding residual volume, and incontinence.
The trial also did not reveal any subgroup of patients, such as men with higher PSA levels or men with lower peak uroflow, who showed "a clinically important differential response" to saw palmetto, compared with placebo.
At the conclusion of the study, two measures of patient satisfaction with treatment did not differ between the two groups. Both men who received saw palmetto and men who received placebo rated their symptoms as "between ‘a little better’ and ‘about the same.’ "
This study was supported by the National Institutes of Health, 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 extract and matching placebo gelcaps were donated by Rottapharm/Madaus, Cologne, Germany. This study was conducted under an Investigational New Drug Application from the Food and Drug Administration. Dr. Barry’s associates reported ties to numerous industry sources.