Arecaceae
Serenoa repens
Saw palmetto
- Part used
- fruit
- Native range
- Southeastern United States, chiefly Florida
- Morphology
- A low clumping palm with fan leaves whose stalks carry sharp teeth, spreading by creeping stems. Slow-growing and very long-lived; some clones are estimated in the hundreds of years.
- Also known as
- Sabal serrulata
What is in it
Evidence
Early trials were positive; the larger and better-blinded ones were not. A well-run dose-escalation trial found no benefit over placebo for lower urinary tract symptoms even at triple the usual dose, and Cochrane concurs.
Safety
Well tolerated, with mild gastrointestinal effects the commonest complaint. Rare hepatotoxicity is reported. May lower prostate-specific antigen readings, which can mask a rising PSA and delay a prostate cancer diagnosis — a genuine and under-appreciated harm.
Interactions: Theoretical additive effect with anticoagulants; May confound PSA screening
Regulatory: Permitted as a listed medicine ingredient in Australia and widely sold over the counter.
Historical use
Used by the Seminole and other southeastern peoples as food and medicine. Adopted by the Eclectic physicians for urinary complaints in the late nineteenth century.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
What it is taken for, and who says so
Sold in very large volume for benign prostatic hyperplasia and urinary symptoms in men, and it remains one of the best-selling men's supplements despite the trial results.
Recorded because it is what people believe, not because it is what the plant does. Whether any of it holds up is the Evidence section above, and the two frequently disagree. A sincere account of feeling better is compatible with the plant doing nothing — see the placebo effect.
Worth knowing
Saw palmetto is the textbook case of an effect shrinking as the trials get better — early small studies positive, later large blinded ones flat, and a dose-escalation design finally ruling out the "they used too little" defence.
The harm worth knowing is not toxicity. It lowers PSA, which is the number used to screen for prostate cancer. A man taking it for urinary symptoms can produce a reassuring reading while a tumour is developing, and neither he nor his doctor will necessarily connect the supplement to the result.
Harvest is almost entirely from wild stands in Florida, where the berries are also a critical food for black bears and other wildlife, and permitting has tightened as a result.
Nomenclature verified against GBIF backbone taxonomy.