Skip to main content


Studies in Men with Enlarged Prostates:

Since 1998 there have been at least 5 meta-analyses on clinical trials investigating the effect of saw palmetto on men with enlarged prostates, aka benign prostatic hyperplasia (1,2,3,4,5).  The most recent 2012 meta-analysis included 32 randomized, controlled trials, involving a total of 5666 men.  Those assigned to the supplement treatment group in these studies, received between 100-960 mg of saw palmetto, by itself or in combination with other natural ingredients, every day for 4 to 72 weeks.  Analysis of all the adverse events associated with saw palmetto lead to the conclusion that there is no significant difference in the relative risk of adverse events between saw palmetto and placebo (1).

While data about the safety and tolerability of saw palmetto tend to be consistent across studies (1,6,7) findings regarding its effect on the symptoms of benign prostatic hyperplasia (BPH) vary greatly.  Based on the 2012 meta-analysis, there were 11 trials that urinary symptom-scale score outcomes and compared patients treated with saw palmetto alone vs. placebo.  Significant improvements in urinary symptom scores for saw palmetto treatment groups relative to placebo was seen in 7 of those 11 trials.  Only one of those 7 trials, however, used a validated urinary symptom-scale score (the International Prostate Symptom Score or the American urological Association Symptom Score) while the rest used non-validated self-rated surveys or physician-assessed symptom improvement questionnaires.  These 7 trials were also all relatively small and ‘underpowered,’ and most were of short duration (1).  Among the 4 remaining trials there were two that that had large enrollment (225 and 357 patients) and lasted for a year or longer (8,9).  These trials used validated urinary symptom-scale scores and showed that there was no significant difference between the saw palmetto and the placebo groups in urinary symptom changes.  They also reported quantitative measurements and showed no significant difference between the saw palmetto and placebo groups in terms of peak urine flow, residual urine volume, or prostate-specific antigen level (1,8,9).

The authors of the latest meta-analysis acknowledged the ambiguity in the evidence but were inclined to put more weight on the ‘high-powered,’ well designed, and long duration studies.  As such, they concluded that there is little evidence indicating that saw palmetto is more effective than placebo in improving urinary symptoms consistent with BPH (1).  The most recent guidelines for BPH management from the American Urological Association reflect this conclusion with the caveat that “further studies are ongoing, and more definitive evidence regarding the use of saw palmetto [is] forthcoming” (10).

It should be noted, however, that the effect of saw palmetto in mixed supplements has not yet been determined.  More studies are needed to determine if saw palmetto can act synergistically with other ingredients to relieve the symptoms of BPH.


  1. Tacklind J, MacDonald R, Rutks I, Stanke JU, Wilt TJ. Serenoa repens for benign prostatic hyperplasia. Cochrane Database of Systematic Reviews. 2012;12. doi:10.1002/14651858.CD001423.pub3.
  2. Tacklind J, MacDonald R, Rutks I, Wilt TJ. Serenoa repens for benign prostatic hyperplasia. Cochrane Database of Systematic Reviews. 2009;2. doi:10.1002/14651858.CD001423.pub2.
  3. Boyle P, Robertson C, Lowe F, Roehrborn C. Updated meta-analysis of clinical trials of Serenoa repens extract in the treatment of symptomatic benign prostatic hyperplasia. BJU Int. 2004;93(6):751-756. doi:10.1111/j.1464-410X.2003.04735.x.
  4. Wilt TJ, Ishani a, MacDonald R. Phytotherapy for benign prostatic hyperplasia. Public Health Nutr. 2000;3(4A):459-472. doi:10.1017/S1368980000000549.
  5. Wilt TJ, Ishani A, Stark G, MacDonald R, Lau J, Mulrow C. Saw palmetto extracts for treatment of benign prostatic hyperplasia: a systematic review. JAMA. 1998;280(18):1604-1609. doi:10.1001/jama.280.18.1604.
  6. Avins AL, Bent S, Staccone S, et al. A detailed safety assessment of a saw palmetto extract. Complement Ther Med. 2008;16(3):147-154. doi:10.1016/j.ctim.2007.10.005.
  7. Avins Al, Lee JY, Meyers CM, Barry MJ, CAMUS Study Group. Safety and toxicity of saw palmetto in the CAMUS trial. J Urol. 2013;189(4):1415-1420. doi:10.1016/juro.2012.10.002.
  8. Bent S, Kane C, Shinohara K, Neuhaus J, Hudes E, Goldberg H, Avins AL. Saw palmetto for benign prostatic hyperplasia. New Engl J of Med. 2006;354(6):557-566. doi:10.1056/NEJMoa053085.
  9. Barry MJ, Meleth S, Lee JY, et al. Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: a randomized trial. JAMA. 2011;306(12):1344-1351. doi:10.1001/jama.2011.1364.
  10. Management of Benign Prostatic Hyperplasia (BPH). American Urological Association. Originally published 2010 and validity confirmed 2014. Accessed April 25, 2018.