Saw Palmetto: Which Dose Is Worth Buying, and Which Is Decoration
Plant guide · The Prostate Herb Desk · updated 2026-10-04
The number that decides whether a saw palmetto product is worth buying is 320 mg of a standardised extract — that is what almost every positive trial used. The formulas we track carry 300, 100, 94.5 and 33.3 mg. One of those is in range and one is a tenth of it, and nothing on the front of either box tells you which.
The honest version of the research
Saw palmetto has been through more randomised trials than any other herb on this site, and the results split along a line that’s easy to miss.
Earlier European trials, generally using a specific standardised hexane extract at 320 mg daily, reported improvements in urinary symptom scores. Later, larger and more rigorously controlled American trials — including ones that escalated the dose well beyond 320 mg — found no significant difference from placebo on symptom scores.
The two camps argue about extract quality, trial length, and who was enrolled. What nobody serious argues is that saw palmetto shrinks the prostate. It doesn’t. The claim on the table has always been symptom relief, not a change to the gland.
Where that leaves a reasonable person: a plant with a long record, a real mechanism story, mixed high-quality evidence leaning negative in the strictest trials, and a very good safety profile. Worth trying, with modest expectations and a time limit.
320 mg is the number that matters
Almost every positive trial used 320 mg a day of a lipidosterolic extract standardised to 85–95% fatty acids and sterols. That standardisation is the active part. Dried berry powder at the same milligram count is not the same material.
Now the labels. Of the formulas we track: one carries 300 mg, which is in range. One carries 100 mg. One carries 94.5 mg. One carries 33.3 mg.
Thirty-three milligrams of saw palmetto is a tenth of the studied dose. No reading of the research supports expecting anything from it. It’s there so the name can be printed on the panel.
How it’s thought to work
Two proposed mechanisms, neither fully settled. It may weakly inhibit 5-alpha-reductase, the enzyme that converts testosterone to DHT — the same target as the prescription drug finasteride, but far more weakly. And it appears to have anti-inflammatory activity in prostate tissue, which may matter more than the hormonal story.
The weakness relative to the drug is the point, not a footnote. Finasteride measurably shrinks the gland over months. Saw palmetto does not, and any page implying it does is borrowing the drug’s result.
Who it suits
A man with mild to moderate urinary symptoms from a benign, already-examined enlargement, who wants to try something with a long safety record before considering medication, and who will give it eight to twelve weeks and then judge honestly.
Who should leave it alone
Anyone on blood thinners — there are case reports of bleeding, and the risk isn’t worth the modest upside. Anyone scheduled for surgery should stop a couple of weeks before, for the same reason.
And importantly: anyone who hasn’t had the symptoms examined. Saw palmetto can soften symptoms without touching whatever is causing them, and the one thing you don’t want is a slightly more comfortable version of a problem that needed investigating.
The short version
The most-studied prostate herb, with mixed evidence, a real safety record, and no effect on gland size. The number to look for is 320 mg of a standardised extract, and it is the fastest way to sort a shelf: the formulas that reach it are making a different offer from the ones carrying a tenth of it, and the panel is where you find out which you are holding.