Some men elect to use dietary supplements that contain substances derived from plants or minerals to manage symptoms of benign prostatic hyperplasia (BPH, enlargement of the prostate gland). Saw palmetto, which is extracted from the berries of the American saw palmetto plant (Serenoa repens), is the most well-known of these remedies.
Claims, purported benefits: Shrinks the prostate; reduces symptoms of BPH, such as urgent urination or urinary leaking. In some European countries, saw palmetto is an accepted treatment for BPH. It may work, in part, by reducing the activity of the enzyme 5-alpha-reductase, which is how drugs like finasteride and dutasteride work.
What the studies show
Research has produced inconsistent and contradictory results. One of the best studies, in the Journal of the American Medical Association in 2011, tested several doses of a standardized extract in middle-aged men over a 72-week period. Even at three times the standard 320-milligram dose, the saw palmetto did not reduce prostate symptoms. An updated review by the Cochrane Collaboration in 2012 looked at 32 controlled clinical trials on men with BPH and concluded that saw palmetto didn’t improve urine flow, nighttime urination, or other symptoms compared to a placebo. Another review by the same authors that year, in BJU International, looked at 17 trials on saw palmetto products and again found no benefits. It noted, however, that it was unclear whether this was true of standardized proprietary products.
Indeed, one difficulty in evaluating saw palmetto (like other herbs) is the lack of standardization in most products, meaning that active compounds (notably sterols, fatty acids, and flavonoids) vary considerably. This is partly due to different extraction methods. Among the most studied extracts is a French proprietary product called Permixon, which the European Medicines Agency (something like our FDA) has concluded is effective and safe; however, it found insufficient evidence to support the use of other extracts. Many preparations also contain other ingredients that are of questionable value.
Side effects: Be cautious about taking saw palmetto if you have a bleeding disorder or are taking blood thinners, though a 2014 review article on the effect of various herbs on warfarin concluded that an interaction is “doubtful.” Do not take it prior to surgery—it may increase bleeding. It may also not be safe to take the herb with finasteride or some other BPH drugs. Despite concerns that saw palmetto may deceptively lower results of PSA tests (for prostate cancer), a 2013 study found no such effect. Don’t take it if you are allergic to plants in the Arecaceae (palm tree) family.
Bottom line: If you are a man who has urinary symptoms and want to try saw palmetto, talk to your doctor first. You need to make sure what you have is BPH. Keep in mind, the best research so far has cast doubt on the effectiveness of saw palmetto.