Saw palmetto for an enlarged prostate: what trials found and what the NHS offers

Saw palmetto is extracted from the berries of a small palm native to the south-eastern United States. It has been marketed for decades to men with frequent urination, a weak stream and waking at night to pass urine, which are typical of benign prostate enlargement. The idea is that the extract acts a little like finasteride, a licensed medicine that shrinks the prostate.

The expectation has not held up well in trials. A 2023 review concluded that saw palmetto used alone offers little or no benefit for benign prostate enlargement symptoms. Two NIH-funded trials tested a standard dose and then up to three times that dose, and neither improved symptoms. The review found no difference between products extracted with hexane and those made by other methods.

Earlier small studies had seemed encouraging, which shows why larger, well-controlled trials matter. Many men do feel better while taking it, but natural fluctuation in symptoms and the placebo effect can account for that.

Saw palmetto is generally well tolerated. Adverse effects are mild and infrequent and can include digestive symptoms, dizziness and headache, and research has used it safely for up to three years. The NIH page advises anyone taking any medicine to talk to a health professional before using a herbal product.

Unlike finasteride, saw palmetto does not appear to affect prostate-specific antigen readings, even at higher-than-usual doses. That is reassuring in one sense, since it should not mask a rise. But it also means a stable PSA while taking it tells you nothing about whether the supplement is working, and a rising PSA should never be dismissed because you take a herbal remedy.

Urinary symptoms can come from an enlarged prostate, but also from infection, diabetes, medicines, bladder problems and, sometimes, prostate cancer. The NHS says an enlarged prostate does not cause prostate cancer or raise the risk of it, yet symptoms still need professional evaluation to rule out other causes.

• See a GP for difficulty peeing or needing to pee more often.

• Get urgent help for blood in the urine, pain on passing urine, or being unable to pass urine.

• A burning sensation with fever or loin pain may be an infection and needs same-day advice from the GP or NHS 111.

NHS self-help advice for an enlarged prostate includes cutting down on alcohol and caffeine, limiting drinks before bed while staying hydrated in the day, eating more fibre, keeping to a healthy weight, double-voiding and gentle pressure behind the scrotum after urinating, and reviewing other medicines that may contribute.

Medicines include tamsulosin and doxazosin, which relax the prostate and bladder neck, and finasteride, which reduces prostate growth. Surgery such as transurethral resection of the prostate may be offered when medicines fail or symptoms are severe, and bladder training and pelvic floor exercises can help too. These are described in more detail in the linked guides below.

Saw palmetto may be unsafe in pregnancy or breastfeeding. This matters less for men, but partners handling opened capsules or crushed tablets should be aware. Interaction data are limited, so the sensible approach is to tell your GP and pharmacist you take it, particularly if you are on anticoagulants or hormone-related treatments.

In the UK, products are sold both as food supplements and as registered traditional herbal medicines carrying a THR mark. A registered product has met standards for safety, quality and information, but the registration does not mean the MHRA has judged the product effective.