Saw Palmetto Extract

Updated October 7, 2026 · By Marcus Reid

What is Saw Palmetto Extract?

Saw palmetto is a small palm (Serenoa repens, also classified as Sabal serrulata) native to the southeastern United States. The berries of this plant have been used for centuries by Native Americans for urinary and reproductive health. In supplement form, saw palmetto is available as dried berry powder, liposterolic extract (standardized to fatty acids and sterols), or supercritical CO2 extract. The extract form — standardized to 85–95% fatty acids and sterols — is the preparation most commonly studied in clinical trials.

How it works

Saw palmetto's proposed mechanisms center on inhibiting 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT). Elevated DHT is associated with prostate tissue growth. In vitro studies confirm that saw palmetto fatty acids can inhibit both type I and type II 5-alpha-reductase isoenzymes. Additional proposed mechanisms include anti-inflammatory activity through cyclooxygenase and lipoxygenase inhibition, smooth muscle relaxation in the lower urinary tract, and modulation of growth factor signaling in prostate epithelial cells. However, a key caveat: the CAMUS trial demonstrated that even at escalated doses (up to 960 mg daily), saw palmetto did not reduce serum DHT levels in men with BPH, suggesting that the 5-alpha-reductase inhibition observed in vitro may not fully translate to oral supplementation in vivo.

What the evidence says

Saw palmetto has more clinical trial data than any other prostate botanical, but the evidence remains genuinely mixed. Earlier meta-analyses and European regulatory reviews supported its efficacy, while more recent large-scale randomized trials have been less favorable.

• A 2025 systematic review found recent evidence supporting saw palmetto for BPH symptom improvement. — This systematic review searched PubMed, Cochrane, and ScienceDirect for human studies from January 2020 to May 2025 on Serenoa repens for benign prostatic disorders. Recent observational studies and some RCTs reported improvements in urinary symptom scores (IPSS) with 320 mg daily of standardized extract over periods of 12 to 24 months. (Systematic review, PMC (2025))
• The CAMUS trial found no improvement in LUTS with saw palmetto at doses up to 960 mg daily over 72 weeks. — A large multicenter, randomized, double-blind, placebo-controlled trial tested escalating doses of saw palmetto extract (320 mg for 24 weeks, 640 mg for 24 weeks, then 960 mg for 24 weeks) in men with moderate LUTS. The primary outcome (AUASI score change) did not differ significantly from placebo at any dose level. (Barry et al. (2011), JAMA)
• A pilot trial showed 320 mg saw palmetto improved BPH symptoms and sexual dysfunction scores. — An open-label pilot study of 82 men taking 320 mg saw palmetto extract daily for 8 weeks found statistically significant improvements in IPSS, quality of life scores, and sexual function measures including erectile function and intercourse satisfaction. (Speroni et al. (2012), Phytomedicine)
• Saw palmetto improved urinary symptom scores and nocturia versus placebo in a pooled analysis of 18 RCTs. — A 1998 JAMA systematic review analyzed 18 randomized controlled trials involving 2,939 men. Men treated with Serenoa repens had decreased urinary tract symptom scores (weighted mean difference -1.41 points) and reduced nocturia (weighted mean difference -0.76 episodes/night) compared with placebo. (1998, JAMA (PMID 9820264))
• A rigorous double-blind trial found saw palmetto 320 mg/day did not improve BPH symptoms versus placebo. — A 2006 New England Journal of Medicine trial randomized 225 men with moderate BPH symptoms to 160 mg saw palmetto extract twice daily or placebo for one year. There was no significant difference in the American Urological Association Symptom Index, peak urinary flow rate, or prostate size between groups. (2006, NEJM (PMID 16467543))

Effective dosage

The standard clinical dose is 320 mg daily of standardized liposterolic extract (85–95% fatty acids and sterols), taken once daily or as 160 mg twice daily. This is the dose used in the majority of clinical trials, including the Cochrane review and the CAMUS randomized trial.

Concentrated extracts (e.g., 10:1 ratio) are sometimes used in multi-ingredient formulas, where a lower raw weight theoretically delivers equivalent phytochemical content. However, the clinical evidence base was built on the specific standardized extract, and equivalence of concentrated preparations has not been independently validated in trials.

Doses up to 960 mg daily were tested in the CAMUS dose-escalation trial without improving lower urinary tract symptoms compared to placebo, suggesting that higher doses do not necessarily produce better outcomes.

Safety and interactions

Saw palmetto is well-tolerated in clinical trials, with adverse effects generally mild and comparable to placebo. The most commonly reported side effects are gastrointestinal discomfort, headache, and dizziness. The published safety review data shows no significant impact on PSA levels, liver function, or kidney function at standard doses.

Men taking finasteride, dutasteride, or other 5-alpha reductase inhibitors should consult their physician before adding saw palmetto, as the mechanisms theoretically overlap. Saw palmetto should also be discussed with a doctor before any prostate biopsy or PSA testing, though clinical data suggests it does not meaningfully alter PSA readings.