Saw palmetto

Is saw palmetto safe?

Yes, for most men who take it. Saw palmetto, an extract of the berries of a small palm from the south-eastern US, has some of the best safety data of any herbal supplement. Studies have used it for up to three years, and side effects are mild and infrequent: stomach pain, nausea, headache, dizziness. It does not interfere with PSA tests for prostate cancer.

The catch is not safety but value. Two large US trials found it no better than placebo for urinary symptoms of an enlarged prostate, and many products do not contain what the label says.

How much do people take?

The standard dose in the EU herbal monograph, the reference for licensed medicines, is 320 mg of extract a day, either once or as 160 mg twice a day. The best-studied form is a hexane extract, which the EMA accepts as a well-established medicine for benign prostatic hyperplasia (BPH). An ethanol extract at 320 mg once a day is registered as a traditional herbal medicine. Long-term use is allowed, but the monograph says to see a doctor if symptoms continue, or at once for fever, blood in the urine, painful urination or being unable to pass urine.

Higher doses do not seem to add risk. In the US CAMUS trial, published in JAMA in 2011, 369 men took up to 960 mg a day, three times the usual dose, for 72 weeks. No adverse effects were clearly attributable to saw palmetto.

Side effects and liver reports

The EU monograph lists abdominal pain and headache as common, and nausea, skin rash, rises in liver enzymes and reversible breast enlargement in men as uncommon. Taking it with food helps with stomach upset.

LiverToxLiverToxA free US National Institutes of Health database that summarises what is known about liver injury caused by medicines, herbs and supplements.More in the glossary, the US government database on drug-induced liver injuryDrug-induced liver injuryLiver damage caused by a medicine, herbal product or supplement. It is usually rare and unpredictable, but it can be serious.More in the glossary, says saw palmetto has been implicated in rare cases of liver injury but that its role is uncertain. The EMA's assessment describes single case reports, including acute liver damage in a 58-year-old man and pancreatitis in a 65-year-old man. Given how widely it is used, these remain isolated. Compare that with black cohosh, where dozens of liver cases led to a mandatory EU warning.

Interactions to know about

The EU monograph names one: a few suspected cases of increased INR, a measure of blood clotting time, in people on warfarin. Some national product information in Europe goes further and warns of bleeding when combined with other blood thinners such as clopidogrel, aspirin and anti-inflammatory painkillers, and of intra-operative floppy iris syndrome, a complication in cataract surgery. If you take a blood thinner or are booked for surgery, tell your doctor or pharmacist that you take it.

There is no known harmful interaction with finasteride, the prescription drug most men with BPH or hair loss are offered. But saw palmetto is sometimes marketed as a "natural finasteride", and the comparison does not hold up. Finasteride has strong trial evidence and, at 5 mg, roughly halves PSA, which doctors adjust for. Saw palmetto does neither.

Does it work?

For prostate symptoms, the evidence has turned against it. NCCIH cites a 2023 review of 27 studies that found little or no benefit from saw palmetto alone. Two NIH-funded trials, one at the standard dose and CAMUS at up to triple the dose, found no improvement over placebo, and hexane extracts did no better than other types. For hair loss and chronic prostatitis, the evidence is too thin to judge.

That matters for safety in one way: urinary symptoms in older men can signal other problems, including prostate cancer. Self-treating with a supplement should not delay a check-up.

Is the product what it says?

Often not. Product tests have found fatty acid content, the main quality marker, ranging from 97% below to 140% above the stated amount. Liquid extracts carry the most, while tinctures carry almost none. The American Botanical Council's adulterants programme reports that extracts are sometimes diluted or replaced with cheap vegetable oils or fatty acid blends built to pass basic tests.

Choose a product that names the extract type (hexane or ethanol) and amount, ideally with USP or NSF verification, or a licensed herbal medicine in the UK or EU.

How we scored it

Dose safety (90) and regulatory actions (90) are the strongest factors: long trials with mild side effects and no bans or warnings. Product quality (55) is the weakest because of variable content and adulteration. Saw palmetto scores above ginseng and well above black cohosh, but its weak evidence of benefit is not part of a safety score and is worth weighing before you buy.