Not meaningfully. The two largest placebo-controlled trials — STEP in 2006 and the NIH-funded CAMUS trial in 2011, which used up to 960 mg a day for 72 weeks — found saw palmetto no better than placebo for urinary symptoms, flow rate or prostate size. The 2023 Cochrane review of 27 trials found an average symptom-score improvement of under one point, below what a man can perceive. A specific hexane extract sold as a medicine in Europe has modest positive results of its own. Saw palmetto is safe, so trying it does little harm; relying on it delays treatments that work.
What the trials found
Saw palmetto is the most-sold prostate supplement in the world, and it has been tested more thoroughly than almost any other herbal product. The results are unusually clear.
STEP (2006). 225 men with moderate to severe symptoms of prostate enlargement were randomized to 160 mg of a standardized saw palmetto extract twice daily, or an identical placebo, for a year. Symptom scores, peak urinary flow, residual urine, prostate size and quality of life all changed by the same amount in both groups.
CAMUS (2011). Because critics argued the dose was too low, the U.S. National Institutes of Health funded a second trial: 369 men took saw palmetto escalating to 960 mg a day — three times the usual dose — for 72 weeks. Symptom scores fell by 2.2 points on saw palmetto and 3.0 points on placebo. Nothing else differed: flow, residual volume, PSA, sexual function, sleep.
Cochrane (2023). Pooling 27 randomized trials and 4,656 men, the review found saw palmetto improved symptom scores by 0.9 points more than placebo, with high certainty. Urologists consider a 3-point change the minimum a patient can feel. There was no effect on flow rate or prostate volume.
Why early evidence looked positive
Before 2006, meta-analyses of small trials concluded saw palmetto worked about as well as finasteride. Those trials were mostly short (under 12 weeks), small, often unblinded, and sometimes compared saw palmetto against an active drug without a placebo group. Urinary symptoms fluctuate, improve with the attention that comes from being in a study, and respond strongly to placebo. When rigorous trials were finally run, the effect disappeared.
This is not unique to saw palmetto; it is the usual trajectory for supplements whose evidence base is built on small early trials. It is worth remembering when a product's page cites "clinical studies".
The one exception
A specific extract — the hexane-extracted lipidosterolic product sold in Europe as Permixon — has trials of its own showing modest improvement, in some comparable to tamsulosin, and European urology guidelines give it a weak recommendation. Those trials were largely manufacturer-funded and did not use the rigorous designs of STEP or CAMUS. Even granting them, the extract in most products sold in the US, UK, Canada and Australia is not Permixon, and manufacturers rarely state which extract they use. See saw palmetto for the detail.
What works instead
Men with bothersome urinary symptoms have options with strong evidence:
- Lifestyle measures — evening fluid restriction, less caffeine and alcohol, double voiding, treating constipation, reviewing medications — help at any stage and cost nothing.
- Alpha-blockers (tamsulosin and others) improve symptoms within days.
- 5-alpha reductase inhibitors (finasteride, dutasteride) shrink the gland over months and reduce the risk of retention.
- Minimally invasive procedures and surgery for symptoms that persist.
And a doctor's assessment excludes the other causes of a weak stream or night-time urination that a supplement would not address — infection, stricture, an underactive bladder, or urine produced in excess overnight.
If you still want to try a supplement
Beta-sitosterol at 60–130 mg a day has a small body of older trials showing improved symptoms and flow — better evidence than saw palmetto, though dated. Either is safe. Neither affects PSA. Tell your doctor, set a time limit of a few months, keep a symptom score, and stop if nothing has changed. Our prostate supplement research pages evaluate the commercial products that combine these ingredients.
Frequently asked questions
Why do so many men say it helped them?
Urinary symptoms fluctuate and tend to improve with attention to fluids and habits, and the placebo response in BPH trials is large — placebo groups routinely improve by 2–3 symptom points. A man who starts saw palmetto and improves has no way of knowing whether the supplement did it. That is what randomized trials are for, and they say it did not.
Did the trials use the wrong kind of saw palmetto?
This is the main defence, and it has some merit for the specific hexane extract used in European trials. It does not rescue the products most men buy, which are not that extract, and CAMUS used a well-characterized extract at high dose.
What about combination prostate supplements?
Adding beta-sitosterol, pygeum, nettle, zinc or lycopene to saw palmetto does not create evidence that the combination works; each has weaker evidence than saw palmetto's negative trials. Beta-sitosterol alone has some old positive trials.
Is there any harm in trying it?
Little direct harm — it is well tolerated and does not affect PSA. The harm is indirect: months on an ineffective supplement while symptoms progress, and money that could have gone to a doctor's visit.
References
- JAMA. Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: a randomized trial (CAMUS) (2011). PubMed PMID 21954478. https://pubmed.ncbi.nlm.nih.gov/21954478/
- National Center for Complementary and Integrative Health. Saw Palmetto: Usefulness and Safety (2024). https://www.nccih.nih.gov/health/saw-palmetto
- NIDDK. Prostate Enlargement (Benign Prostatic Hyperplasia) (2024). https://www.niddk.nih.gov/health-information/urologic-diseases/prostate-problems/prostate-enlargement-benign-prostatic-hyperplasia
This page discusses supplement ingredients or categories. It may mention a commercial product, with disclosure. It is general health information, not personal medical advice. Read our editorial policy and medical review policy.