Research review
What does saw palmetto do for men?
Almost every saw palmetto trial studied men, mostly for prostate and urinary symptoms — and the largest, longest of those trials found it no better than placebo, even at three times the standard dose. A separate, much smaller trial found a hair-growth benefit in men using a different, specific extract.
Almost every saw palmetto trial has studied men, mostly for prostate and urinary symptoms — and the largest, best-designed of those trials found saw palmetto no better than placebo, even at three times the standard dose. A separate, smaller trial of a different, specific extract found a hair-growth benefit in men.
What the evidence doesn't support
It doesn't support saw palmetto as a treatment for benign prostatic hyperplasia (BPH), an enlarged prostate, or lower urinary tract symptoms, at any dose sold on a label today. It doesn't support lowering DHT or shrinking the prostate as an alternative to doctor-directed care. It doesn't support a general testosterone or libido boost — the one trial that measured sexual function found no difference from placebo. Where a real, if narrower, benefit does exist — hair growth, using a different specific extract — it doesn't support that finding as proof that "saw palmetto" the ingredient does anything for the prostate; the two research bases use different extracts, doses and outcomes entirely.
What the trials found
The largest body of evidence is on the prostate and urinary side, and it's consistently negative. A 2006 trial randomized 225 men over 49 with moderate-to-severe BPH symptoms to a year of the standard dose (320 mg/day) or placebo, and found no significant difference in symptom scores, urine flow, prostate size, or PSA. The CAMUS trial went further: 369 men took saw palmetto starting at the standard dose and escalating to three times it — 960 mg/day — over 72 weeks, and still found no benefit over placebo on the main symptom score or on any of ten secondary measures, including sexual function and sleep quality. A 2012 Cochrane review then pooled 32 trials across 5,666 men and reached the same conclusion at the largest scale yet: no improvement over placebo in symptom scores, urine flow, or prostate size, even at double and triple the standard dose.
The mechanistic story comes from a laboratory study, not a trial: researchers exposed human prostate cells to a specific extract and found it blocked 5-alpha-reductase, the enzyme that converts testosterone into DHT, without reducing the cells' PSA output. That's a real finding about cells in a dish — it isn't a measurement of DHT, testosterone, or symptoms in a man taking a capsule, and none of the placebo-controlled trials above found the clinical benefit that mechanism would predict.
Separately from all of that, a placebo-controlled trial tested a different, specific saw palmetto extract (160 mg/day, not the standard 320 mg/day) for self-perceived hair thinning in 60 adults, including men. In the men-only subgroup, the treated group showed significantly more hair count and density than placebo at 180 days. That's a genuine result — from a different extract, dose and outcome than the prostate research, tested in one trial not yet independently replicated. Full detail is in does saw palmetto help hair growth?
Questions people ask
What does saw palmetto do for men?
Most research tested it for prostate and urinary symptoms, and the largest, longest trials found no benefit over placebo, even at triple the standard dose. A separate, specific extract showed a hair-growth benefit in a smaller placebo-controlled trial. There's no research support for a testosterone or general vitality benefit.
Is saw palmetto good for the prostate?
The largest trials say no. A 2012 Cochrane review of 32 trials in 5,666 men found no significant difference between saw palmetto and placebo in prostate size, symptom scores, or urine flow — even at double and triple the standard dose. Two large individual trials (225 and 369 men) reached the same conclusion on their own.
Does saw palmetto help with erectile function?
No trial we found tested it for that directly. The one large trial that measured sexual function as a secondary outcome (CAMUS) found no difference between saw palmetto and placebo on that measure.
What is the saw palmetto dosage for men?
The dose used across the largest prostate trials is 320 mg/day of standardized extract, split into two doses; see how much saw palmetto should you take a day. The hair trial above used a different, specific 160 mg/day extract — the two aren't interchangeable.
When to talk to a doctor
Saw palmetto is not a treatment for benign prostatic hyperplasia, an enlarged prostate, or urinary symptoms. Frequent, urgent, weak or painful urination, blood in the urine, or a rapidly enlarging prostate are reasons to see a doctor rather than try a supplement, since some of those symptoms can signal a condition a supplement search wouldn't catch.
Related reading: saw palmetto benefits: what the research does and doesn't show, does saw palmetto help hair growth?, and does saw palmetto raise or lower testosterone?
Sources
- Serenoa repens for benign prostatic hyperplasia A Cochrane review pooling 32 randomized trials in 5,666 men found saw palmetto, even at double and triple the standard dose, was no better than placebo for urinary symptom scores, urine flow, or prostate size.
- Saw palmetto for benign prostatic hyperplasia A one-year randomized trial in 225 men found the standard dose of saw palmetto extract (320 mg/day) performed no better than placebo on urinary symptom scores or urine flow.
- Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: a randomized trial A 72-week randomized trial that escalated saw palmetto up to triple the standard dose (960 mg/day) in 369 men found it did not reduce urinary symptoms more than placebo at any dose tested.
- Serenoa repens (Permixon) inhibits the 5alpha-reductase activity of human prostate cancer cell lines without interfering with PSA expression A laboratory study found one specific saw palmetto extract blocked an enzyme that converts testosterone to DHT in cultured prostate cells, without lowering PSA production in those cells — a cell-culture finding, not proof it changes hormone levels in someone taking a capsule.
- The Safety and Efficacy of a Proprietary Bioactive Fatty Acids Extract From Saw Palmetto (Serenoa repens) for Promoting Hair Growth and Reducing Hair Loss in Adults With Self-Perceived Thinning Hair: 90-Day Results A placebo-controlled trial of a specific 160 mg/day saw palmetto extract found significantly greater hair counts than placebo at 90 days in 60 adults, half of them women.
- The Safety and Efficacy of a Novel Saw Palmetto (Serenoa repens) Extract for Promoting Hair Growth in Adults With Self-Perceived Thinning Hair: 180-Day Results The 180-day results of the same trial found the treated group's advantage over placebo grew larger between Day 90 and Day 180, in both men and menopausal women.
- Serenoa repens (saw palmetto): a systematic review of adverse events A systematic review of 40 studies found saw palmetto's side effects are usually mild and similar in frequency to placebo — mainly stomach upset, headache, fatigue and decreased libido — with serious events reported only in isolated case reports of uncertain cause.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.