Saw palmetto, a herbal extract taken by more than two million US men for relief from the symptoms of benign prostatic hyperplasia, showed no benefit over placebo, a study has found. The year long, double blind, randomised trial was reported this week in the New England Journal of Medicine (2006;354:557–66). The herbal extract, taken from the berries of a small, palm–like north American plant, is commonly recommended as an alternative to prescription drugs.
An accompanying editorial says additional rigorous, placebo controlled studies are needed before conclusions can be made about the long term effectiveness and safety of other saw palmetto preparations and that herbal remedies should be subjected to clinical trials of the same quality needed for approval of standard drugs.
Until this is done, it says, doctors are responsible for protecting patients from the risks of unproved therapies.
The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the National Centre for Complementary and Alternative Medicine. These institutions, like the supplier of saw palmetto, had no role in the study’s design or conduct, in the collection, management, analysis, and interpretation of the data, or in the preparation, review, and approval of the manuscript. The only potential conflicts of interest were stated by three of the authors, who acknowledged having had consulting or lecture fees or grants from drug manufacturers.
In the trial, which took place between July 2001 and May 2004, the authors randomly assigned 225 of 775 men (aged over 49) who had been screened for eligibility and who had moderate to severe symptoms of benign prostatic hyperplasia to either a year of treatment with saw palmetto extract (160 mg twice a day) or a placebo.
The participants had symptoms that scored at least 8 of a possible 35 for severity on the American Urological Association symptom index and had a peak urinary flow rate of less than 15 ml per second.
They were recruited from the San Francisco Veterans Affairs Medical Centre, Kaiser Permanente Northern California, and the surrounding community. A total of 113 received placebo, and 112 took saw palmetto.
The primary outcome measures were changes in score on the American Urological Association symptom index and the maximal urinary flow rate. Secondary outcome measures included changes in prostate size, residual urinary volume after voiding, quality of life, laboratory values, and reported adverse effects.
The authors found no differences between the saw palmetto and placebo groups in the change in symptom index scores, maximal urinary flow rate, prostate size, residual volume after voiding, quality of life, or serum prostate specific antigen levels over the 12 months. The incidence of side effects was similar in the two groups.
Although most earlier randomised trials of saw palmetto reported small improvements in benign prostatic hyperplasia symptoms or in urinary flow rates, the authors say that such studies are limited by their small numbers of subjects, short duration, failure to use standard outcome measures, and lack of information on how effectively the trial was double blinded. They say that these faults were avoided in their study.