Increasing dosage of saw palmetto does not appear to reduce urinary symptoms from enlarged prostate

"Benign prostatic hyperplasia [BPH; an enlarged prostate gland] is a common cause of bothersome lower urinary tract symptoms (LUTS) among older men and may be treated with medications, minimally invasive therapies, or surgery. Plant extracts are also widely used for LUTS in the United States and Europe. The most common are extracts of the fruit of the saw palmetto dwarf palm tree," according to background information in the article. In a 2007 U.S. survey, 17.7 percent of adults reported use of a natural product in the last 30 days and 5.1 percent of users had taken saw palmetto. Several recent clinical trials have questioned the efficacy of the use of saw palmetto in treating LUTS. Symptoms of LUTS may include urination frequency, urgency and hesitancy.

Michael J. Barry, M.D., of Massachusetts General Hospital, Boston, and colleagues conducted a study 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 LUTS attributed to BPH. The multicenter, placebo-controlled randomized trial was conducted at 11 North American clinical sites between June 2008 and October 2010. The trial included 369 men, ages 45 years or older, with a certain minimum peak urinary flow rate and an American Urological Association Symptom Index (AUASI; a self-administered 7-item index assessing frequency of LUTS [range, 0-35 points]) score of between 8 and 24 at 2 screening visits. Participants received 1, 2, and then 3 doses (320 mg/d) of saw palmetto extract or placebo, with dose increases at 24 and 48 weeks.

In an analysis of the group average changes in AUASI scores between the beginning of the study and at 72 weeks, the AUASI score decreased an average of 2.20 points with saw palmetto extract and 2.99 points with placebo, a group average difference of 0.79 points favoring placebo. "The proportion of participants achieving a 3-point decrease in AUASI score at 72 weeks was 42.6 percent in the saw palmetto extract group and 44.2 percent in the placebo group," the authors write. "In addition, the analysis of dose response also showed no greater improvement with saw palmetto extract vs. placebo at any dose level."

The researchers also found that saw palmetto extract was no better than placebo for any of the secondary outcomes, including measures of urinary bother, nocturia (excessive urination at night), and indices of sexual function, continence, sleep quality, and prostatitis symptoms. No clearly attributable adverse effects were identified.

"In conclusion, we found that saw palmetto extract used at up to 3 times the standard daily dose had no greater effect than placebo on improving lower urinary symptoms or other outcomes related to BPH."