Despite its popularity, the scientific evidence that saw palmetto is effective for prostate enlargement is inconsistent at best.

In the most recent and perhaps best-designed study, a 1-year trial of 225 men, saw palmetto failed to prove more effective than placebo. Furthermore, a large review of 14 trials with 5,222 men found that saw palmetto did not improve urinary symptom scores or peak urine flow compared to placebo.

Adding to the unsupported evidence, a more recent well designed, placebo-controlled trial involving 369 men found that saw palmetto even at high doses (three times the standard dose) did not improve urinary flow rate compared to placebo.

  • Bent, Stephen; Kane, Christopher; Shinohara, Katsuto; Neuhaus, John; Hudes, Esther S.; Goldberg, Harley; Avins, Andrew L. (2006). “Saw Palmetto for Benign Prostatic Hyperplasia”. New England Journal of Medicine 354 (6): 557–66. doi:10.1056/NEJMoa053085.PMID 16467543.
  • Dedhia, R; McVary, K (2008). “Phytotherapy for Lower Urinary Tract Symptoms Secondary to Benign Prostatic Hyperplasia”. The Journal of Urology 179 (6): 2119–25. doi:10.1016/j.juro.2008.01.094.PMID 18423748.
  • Tacklind, J; MacDonald, R; Rutks, I; Wilt, TJ (2009). Tacklind, James, ed. Serenoa repens for benign prostatic hyperplasia”. Cochrane Database of Systematic Reviews (2): CD001423.doi:10.1002/14651858.CD001423.pub2. PMC 3090655.PMID 19370565.