Serenoa repens · herb
Evidence tier: insufficient
Reduces DHT to support prostate health in benign prostate enlargement, also used for male pattern hair loss through 5-alpha reductase inhibition
The marketing mechanism is that the fatty acids and phytosterols in the berry inhibit 5 alpha reductase, the enzyme that converts testosterone into DHT, in the same broad way finasteride does. This is a laboratory story, not a demonstrated one. It matters that the two definitive trials tested exactly the standardised fatty acid extract this mechanism predicts should work, at up to three times the usual dose, and found nothing. Whatever the extract does in a test tube, it does not translate into a clinical effect in men at the doses people take.
This is not an ingredient that is under studied. It is an ingredient that has been studied very well and found not to work. Saw palmetto is one of the best selling men's supplements in the world and its flagship claim, relief of urinary symptoms from an enlarged prostate, has been tested twice by large NIH funded trials and failed both times. The STEP trial randomised 225 men to 320 mg daily for one year and reported that saw palmetto did not improve symptoms or objective measures of benign prostatic hyperplasia (Bent, New England Journal of Medicine 2006, PMID 16467543). The CAMUS trial then escalated 369 men through 320, 640 and finally 960 mg daily over 72 weeks and concluded that increasing doses of a saw palmetto fruit extract did not reduce lower urinary tract symptoms more than placebo (Barry, JAMA 2011, PMID 21954478). Triple dose changed nothing. Cochrane has updated its review to match: across 27 studies in 4,656 men, Serenoa repens alone provides little to no benefits for men with lower urinary tract symptoms due to benign prostatic enlargement, and Cochrane rates that finding HIGH certainty (Franco 2023, CD001423.pub4, PMID 37345871). The pooled difference on the symptom score was 0.9 points on a 35 point scale, far below the roughly 3 points a man would actually notice. NCCIH states plainly that saw palmetto is probably not helpful for this purpose. For male pattern hair loss NCCIH says the evidence is too limited to allow conclusions to be reached. Safety is the one place saw palmetto reads well: adverse events in Cochrane were no different from placebo (risk ratio 1.01), NCCIH calls it well tolerated with up to three years of study exposure, and it does not appear to distort PSA readings. NIH LiverTox assigns likelihood score D, a possible but rare cause of liver injury, with cases self limiting and no deaths or transplants recorded.
320 mg daily of an extract standardised to 85 to 95 percent free fatty acids is the dose used in the definitive trials. Note what that number now means: it is the dose at which the effect was shown to be absent, not the dose at which it works. CAMUS also tested 640 and 960 mg daily with no benefit.
Take 160mg of standardised lipid sterolic extract twice daily with food, or 320mg once daily. Allow 3 to 6 months to assess benefit for prostate or hair loss support.
Generally well tolerated. Mild GI side effects (nausea, stomach upset) are the most common adverse effect. May reduce PSA levels by up to 50%, inform a doctor before PSA cancer screening. Avoid with anticoagulants and hormonal medications. Not for women or children.
Pregnancy: avoid
Breastfeeding: avoid
Active compounds: free fatty acids (lauric, oleic, myristic), phytosterols (beta sitosterol), polysaccharides, flavonoids
Remedies using Saw Palmetto · Browse by body system · Check it against what you take
*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.