Saw palmetto for benign prostatic hyperplasia: just how effective is it?

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Saw palmetto is widely used for the treatment of benign prostatic hyperplasia (BPH), and is generally accepted as an effective alternative to pharmaceutical intervention. The efficacy trials to date, however, have been short in duration, with small patient numbers, inadequate blinding, and a lack of standardized endpoints.


To determine whether saw palmetto is an effective treatment for BPH.


This randomized, double-blind study was conducted in men aged >49 years with moderate-to-severe BPH symptoms, between July 2001 and May 2004. Inclusion criteria were an American Urological Association Symptom Index (AUASI) score of ≥8, and a peak urinary flow rate of <15 ml/s. The main exclusion criteria were a peak urinary-flow rate of <4 ml/s, postvoid residual volume of >250 ml, or PSA level of >4.0 ng/dl, and a history of prostate cancer, BPH surgery, urethral stricture, or neurogenic bladder. Alpha-blocker use and 5α-reductase inhibitor use were discontinued ≥1 month and ≥6 months, respectively, before randomization. A 1-month, single-blind placebo run-in period was used to select patients with ≥75% adherence. Randomization was stratified by AUASI score; outcomes were analyzed on an intent-to-treat basis.


Patients were randomly allocated to 12-month treatment with either saw palmetto (160 mg twice daily) or a placebo.


The primary endpoints were changes in AUASI scores and peak urinary-flow rates. Secondary endpoints included changes in BPH-related and overall quality-of-life measures, prostate size, and postvoid residual volume, and patient-reported side effects.


Of 225 eligible men, 112 received saw palmetto, and 133 received a placebo. The mean age was 63.0 ± 7.7 years. There were no significant differences in baseline variables between the groups, except that patients in the saw-palmetto group had a higher BPH Impact Index score (P = 0.02). Nor were there any significant differences in adherence; 92% of all medication was taken. Over the 12-month treatment period, there were no significant differences in the mean changes in AUASI score or peak urinary-flow rate between the groups. AUASI score decreased by 0.68 points (95% CI −1.37 to 0.01) in the saw-palmetto group, and by 0.72 points (95% CI −1.4 to −0.04) in the placebo group. Peak urinary-flow rate increased by 0.42 ml/s (95% CI −0.25 to 1.10) in the saw-palmetto group, and decreased by 0.01 ml/s (95% CI −0.68 to 0.66) in the placebo group. There were no significant differences between the groups in any of the secondary endpoints investigated. Preplanned analyses of subgroups stratified by AUASI score, prostate size, and PSA level failed to show any benefit of saw palmetto over placebo. Adverse events were similar for the two treatments. At the study end, 40% of men in the saw-palmetto group, and 46% of men in the placebo group, believed they were taking the active drug (P=0.38).


In this 12-month study, saw palmetto was no more effective than placebo in relieving the symptoms or objective measures of BPH.

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