Saw Palmetto (Serenoa repens)
Saw palmetto is an extract of Serenoa repens berries widely marketed as a natural 5-alpha-reductase inhibitor for benign prostatic hyperplasia and hair loss. Evidence is mixed: some trials suggest modest symptom benefit in BPH, but rigorous studies often find effects no better than placebo, and hair-loss data are weak.
01 Overview
Sold as a dietary supplement, saw palmetto is popular among men seeking a milder alternative to finasteride. Its liposterolic extract is proposed to inhibit 5-alpha-reductase and reduce DHT, though far less potently than pharmaceutical 5ARIs.
High-quality trials (e.g. large NIH-funded BPH studies) have generally failed to show benefit over placebo, while hair-loss evidence is limited to small studies. It is generally well tolerated, which sustains its use despite modest efficacy.
02 Mechanism
Fatty-acid/sterol extract proposed to weakly inhibit 5-alpha-reductase and reduce DHT, and to have anti-inflammatory and receptor-binding effects on prostate and follicle tissue.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Standard | 160–320 mg/day | Oral | Standardised liposterolic extract 320 mg/day (or 160 mg twice daily) |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Modest BPH symptom reliefSome studies show minor symptom improvement; well-controlled trials often show no benefit over placebo. | Small or none | Disputed | |
| Possible hair-loss benefitSmall studies and anecdote suggest mild benefit; evidence is limited. | Weak | Anecdotal |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Gastrointestinal upsetNausea or stomach discomfort, usually mild. | Mild | Uncommon | Clinical | |
| Mild anti-androgen effectsOccasional reports of reduced libido; unclear given weak DHT effect. | Mild | Rare | Anecdotal |