Saw palmetto
Summary
For urinary symptoms from an enlarged prostate, a 2023 Cochrane review of 27 trials (4,656 men) found saw palmetto makes little to no difference vs placebo, high-certainty evidence (no effect). Two large US trials at 320–960 mg/day agree. Hair-loss evidence is limited to small trials of mixed products and is too weak to grade. Side effects resemble placebo.
Key facts
- Prostate-related urinary symptoms: little to no difference (no effect, high certainty); hair: too little evidence to grade (small mixed-product trials)[1][2][3][4]
- None set; saw palmetto is not a nutrient[1]
- No drug interactions found in a systematic review of human safety data[5]
- Mild stomach pain, diarrhoea, nausea, fatigue, headache, lower libido; overall rates similar to placebo[1][5]
- 3 graded human outcomes on this page
- October 10, 2026
How it works
ProposedSaw palmetto extracts are proposed to act on male hormone pathways, including weak inhibition of 5-alpha-reductase, the enzyme that turns testosterone into dihydrotestosterone (DHT), plus anti-inflammatory effects on prostate tissue. These ideas come largely from lab work; large human trials did not find changes in prostate size or PSA.[1][2][4]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Urinary symptoms from benign prostatic enlargement | No effect | No effect | Systematic review · n = 4,656 · 2023 Men, mostly over 50, with moderate lower urinary tract symptoms; 27 trials Form: Serenoa repens extracts alone or with other herbs · Dose: Varied; most commonly 320 mg/day · Duration: 3–17 months Little to no difference vs placebo in IPSS symptom scores at 3–6 months (MD −0.90 points on a 0–35 scale, high certainty) and at 12–17 months (MD 0.07), and in quality of life. Adverse events similar to placebo. | 37345871 (opens PubMed)Source [1] |
| Lower urinary tract symptoms at increasing doses | No effect | No effect | RCT · n = 369 · 2011 Men 45 or older with AUA symptom scores of 8–24 Form: saw palmetto fruit extract · Dose: 320, then 640, then 960 mg/day (raised at 24 and 48 weeks) · Duration: 72 weeks Symptom scores fell 2.20 points with saw palmetto and 2.99 points with placebo; no secondary outcome favoured saw palmetto. No clearly attributable adverse effects. | 21954478 (opens PubMed)Source [3] |
| Prostate symptoms and urine flow | No effect | No effect | RCT · n = 225 · 2006 Men over 49 with moderate-to-severe BPH symptoms Form: saw palmetto extract · Dose: 160 mg twice daily (320 mg/day) · Duration: 1 year No difference vs placebo in AUA symptom score, peak urine flow, prostate size, residual volume, quality of life or PSA. Side-effect rates were similar. | 16467543 (opens PubMed)Source [2] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Lipid (lipidosterolic) berry extract, often standardized to 85–95% fatty acids | Varies[1] | Large trials of extracts at 320–960 mg/day showed no symptom benefit over placebo; no human absorption data in our sources.[2][3] | Side effects similar to placebo in trials and in a systematic review of safety data.[1][5] | Prostate symptoms, hair |
| Combination products (saw palmetto with other herbs or nutrients) | Varies[1] | Combinations may give little to no symptom difference in short-term trials (low certainty); hair trials mostly tested combinations, so effects cannot be pinned to saw palmetto.[1][4] | Adverse events probably similar to placebo (low certainty).[1] | Prostate symptoms, hair |
Studied doses
Doses studied in human trials ranged from 320 to 960 mg/day of saw palmetto extract, most often 320 mg/day (160 mg twice daily), for 3 months to 72 weeks. Hair studies used 100–320 mg, often in combination products.[1][2][3][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Medicines
- A systematic review of human safety data found no reported drug interactions. That is an absence of reports, not proof of safety with every medicine; tell your prescriber if you use it alongside prostate or hormone drugs.[5]
- Prostate symptoms
- Urinary symptoms can have causes other than benign enlargement. Large trials found saw palmetto no better than placebo, so relying on it can delay getting symptoms checked.[1][2]
- Pregnancy and breastfeeding
- Saw palmetto is studied almost only in men; there are no pregnancy or breastfeeding safety data in our sources, and it is proposed to act on hormone pathways.[1][5]
- Rare serious reports
- Isolated case reports of serious events exist, but the safety review judged causality questionable.[5]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Label dose vs clinical doseTrials used 160 mg of extract twice daily (320 mg/day), so compare the mg of extract on the label with that. Even at 320–960 mg/day for up to 72 weeks, trial results did not beat placebo for urinary symptoms.[2][3]
- Extract vs whole berry powderThe trials used fatty (lipid) extracts. Ground whole berry powder is a different product that the large trials did not test.[1][2]
- Check for combination formulasHair and prostate blends often add pumpkin seed oil, beta-sitosterol, zinc or other herbs. Combination results cannot be credited to saw palmetto alone.[1][4]
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
Enter the price, servings and the amount per serving from your label.
Frequently asked questions
Does saw palmetto work for an enlarged prostate?
Not according to the best evidence. A 2023 Cochrane review of 27 trials and 4,656 men found little to no difference vs placebo in urinary symptoms or quality of life, with high-certainty evidence.[1]
Does a higher dose of saw palmetto help?
A 72-week trial raised the dose from 320 to 960 mg/day and still found no benefit over placebo for any outcome.[3]
Does saw palmetto help hair loss?
The evidence is weak. A review found small positive trials, but most tested products mixing saw palmetto with other ingredients, and high-quality data are lacking.[4]
What are the side effects of saw palmetto?
Mostly mild: stomach pain, diarrhoea, nausea, fatigue, headache, lower libido. In trials, overall side-effect rates were similar to placebo.[1][5]
Does saw palmetto lower PSA?
In a 1-year trial of 225 men, PSA levels did not differ between saw palmetto and placebo.[2]
Sources
- [1]Serenoa repens for the treatment of lower urinary tract symptoms due to benign prostatic enlargement.. Cochrane Database Syst Rev, 2023. systematic-review
- [2]Saw palmetto for benign prostatic hyperplasia.. N Engl J Med, 2006. RCT
- [3]Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: a randomized trial.. JAMA, 2011. RCT
- [4]Natural Hair Supplement: Friend or Foe? Saw Palmetto, a Systematic Review in Alopecia.. Skin Appendage Disord, 2020. systematic-review
- [5]Serenoa repens (saw palmetto): a systematic review of adverse events.. Drug Saf, 2009. systematic-review
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every claim re-checked against the cited abstract (or full text where noted), PMIDs re-verified via NCBI esummary, unsupported label-market statements removed, two evidence rows with unreported pooled n removed. Page set indexable.