Saw Palmetto

📜 Historical Use

Serenoa repens grows wild across the southeastern United States and the West Indies, a low palm reaching six to ten feet whose berries are the part used. It carries an unusual number of names for a single plant: saw palmetto, American dwarf palm tree and cabbage palm in English, and in the botanical literature Serenoa repens with the synonyms Serenoa serrulata and Sabal serrulatum, which is why older studies can be hard to trace. Its modern history is essentially a research history, and a long one. Controlled trials of standardised extracts run from the mid-1990s — including a 1994 comparison against finasteride and a 1996 trial of over a thousand patients — through the two National Institutes of Health-funded trials of the 2000s to the 2023 Cochrane update that now covers 27 studies. Commercially it is promoted as a dietary supplement for urinary symptoms of an enlarged prostate, and also for male pattern baldness and chronic prostatitis.

📊 What the Research Shows

This is a case where the evidence is unusually good and unusually negative, which is the opposite of the pattern for most herbs. The 2023 Cochrane review of Serenoa repens for lower urinary tract symptoms due to benign prostatic enlargement included 27 studies and 4,656 participants, mostly men over 50 with moderate symptoms. Restricting to trials at low risk of bias, saw palmetto produced a mean difference of -0.90 points on the International Prostate Symptom Score at three to six months, on a scale running from 0 to 35 — high-certainty evidence of little to no difference. Quality of life moved -0.20 points on a six-point domain. At twelve to seventeen months the symptom difference was +0.07, again high certainty, again nothing. Two of the trials were funded by the National Institutes of Health; one used a standard dose and one escalated to three times the usual dose, and neither improved symptoms. Products made by hexane extraction did no better than the rest. Combination products containing saw palmetto plus other herbs showed a larger difference of -2.41 points, but on low-certainty evidence, so the honest statement is uncertainty rather than benefit. Outside BPH the picture is thinner: a 2022 review of five studies in chronic prostatitis and chronic pelvic pain syndrome found no significant benefit, and the handful of small studies of oral or topical saw palmetto for male-pattern hair loss are too limited to support a conclusion either way.

Take 320mg of standardized extract daily.

Hormone modifier. May interfere with oral contraceptives or HRT.

⚠️ What happens if taken in excess:

Generally very safe. High doses (>960mg/day) may cause nausea, headache, dizziness, and diarrhea. Rarely, liver injury has been reported with excessive use. May interfere with hormone-sensitive conditions and contraceptive effectiveness at very high doses. Can increase bleeding risk in surgery.

Neither source read for this page documents a named drug interaction for saw palmetto, and that absence should be reported as an absence rather than dressed up as a clean bill of health — no interaction has been ruled out, it simply has not been catalogued in these two references. What can be said specifically is this. Saw palmetto has been given alongside the drugs men with an enlarged prostate are actually taking: the trials collected by the Cochrane review include studies of tamsulosin, an alpha-blocker, with and without Serenoa repens, and direct comparisons against finasteride, a 5-alpha reductase inhibitor. Co-administration in those trials was not flagged as producing an interaction, though these were efficacy trials and not designed to detect one. The interaction that matters most in this clinical area is the one that does not appear to happen: PSA testing is how prostate disease is monitored, and NCCIH reports saw palmetto does not appear to affect PSA readings even in higher-than-usual amounts, so it does not seem to mask the number the way a reader might reasonably fear. Tell any prescriber you are taking it regardless, and say so before surgery.

1. Efficacy of Serenoa repens for lower urinary tract symptoms: a clinical review — Novara G et al Int Braz J Urol (SBU) (2016)[PubMed ↗]
2. Saw Palmetto — NCCIH — National Institutes of Health NCCIH (NIH) (2020)[NIH ↗]