Saw palmetto berries contain the plant's active ingredients. The active ingredients, thought to be fatty acids, are unidentified but seem to inhibit 5α-reductase, thus opposing the conversion of testosterone to dihydrotestosterone. The berries can be used to make a tea, or they can be extracted into tablets, capsules, or a liquid preparation. Most formulations evaluated in clinical studies are hexane extracts of saw palmetto berries, which are 80 to 90% essential fatty acids and phytosterols.
Strong scientific evidence supports use of saw palmetto to treat symptoms of benign prostatic hyperplasia (eg, frequent urination); no evidence suggests it reverses the hyperplasia. Also, one large, well-designed study did not show any benefit.
Claims that it increases sperm production, breast size, or sexual vigor are unproved. Dose is 320 mg once/day or 160 mg bid.
Headache and diarrhea may occur, but no other serious adverse effects have been reported. Saw palmetto may interact with estrogens; thus, women who are pregnant or who may become pregnant should not take it.
Last full review/revision May 2009 by Ara DerMarderosian, PhD