What is Saw Palmetto
Saw palmetto is a plant extract derived from the berries of the American dwarf palm (Serenoa repens) that is widely used as a dietary supplement for lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH), though high-quality evidence shows it is no more effective than placebo. 1, 2
Botanical Origin and Composition
Saw palmetto extract (SPE) comes from the ripe berries of the American dwarf palm and contains various plant sterols, with beta-sitosterol being the primary active component by weight. 3, 4
The extract contains phytoestrogenic compounds and other constituents whose exact composition and specific effects remain poorly understood. 5
Over 20% of men visiting prostate cancer screening clinics take saw palmetto or similar herbal supplements. 6, 5
Proposed Mechanisms of Action
Multiple mechanisms have been proposed, including inhibition of 5-alpha-reductase (similar to finasteride and dutasteride), binding to alpha-1-adrenoceptors, muscarinic cholinoceptors, and vanilloid receptors in the lower urinary tract. 3, 4
Beta-sitosterol has been shown to promote anti-tumorigenic processes in prostate cancer cells and rodent models through pro-apoptotic effects on prostate epithelial cells. 3
In animal models, SPE attenuates the up-regulation of alpha-1-adrenoceptors in the prostate induced by testosterone and increases bladder capacity in hyperactive bladders. 4, 7
Clinical Efficacy Evidence
The highest quality evidence demonstrates saw palmetto is ineffective for BPH symptoms:
A 2006 double-blind randomized trial of 225 men showed no significant difference between saw palmetto (160 mg twice daily) and placebo in American Urological Association Symptom Index (AUASI) scores, maximal urinary flow rate, prostate size, residual volume after voiding, quality of life, or PSA levels over one year. 1
A 2011 multicenter trial of 369 men testing escalating doses up to 3 times the standard dose (960 mg/day) found saw palmetto no more effective than placebo for any outcome measure, with AUASI scores actually favoring placebo by 0.79 points. 2
One 2009 guideline noted that randomized studies of one Serenoa repens extract (Permixon) suggested superior efficacy against placebo, but comparative studies with other medical treatments were not conclusive due to lack of placebo arms. 8
A 2022 study in Japanese women showed some improvement in daytime urinary frequency and nocturia symptoms, though this represents a different population than typical BPH patients. 7
Clinical Use and Regulatory Status
Saw palmetto is classified as a dietary supplement in the United States, not as an FDA-approved drug for BPH treatment. 8, 1
The 2009 American Urological Association guideline noted that phytotherapeutic preparations vary greatly in manufacturing and extraction procedures, complicating comparisons even when derived from the same plant. 8
Beta-sitosterol supplements may be most appropriate for younger men with minimal LUTS who don't wish to start pharmaceutical drug regimens, as they are generally less effective than alpha-adrenergic receptor antagonists or 5-alpha-reductase inhibitors. 3
Safety Considerations and Drug Interactions
Perioperative bleeding risk:
The Society for Perioperative Assessment and Quality Improvement recommends discontinuing saw palmetto 2 weeks before surgery due to concerns about increased bleeding time, hematuria, and operative bleeding risk through cyclooxygenase inhibition. 6, 9
Data on bleeding risk remain conflicting with inconsistent evidence. 6
PSA monitoring:
Saw palmetto may affect PSA levels through phytoestrogenic compounds, requiring consideration during prostate cancer screening. 6, 5
Treatment that may affect PSA (including saw palmetto) must remain constant during the period when PSA doubling time is being calculated. 8
General safety profile:
Saw palmetto does not have significant interactions with co-administered drugs or serious adverse events in blood biochemical parameters, suggesting relative safety even with long-term intake. 4
The incidence of side effects in clinical trials was similar between saw palmetto and placebo groups. 1
Common Clinical Pitfalls
If a patient taking saw palmetto presents with myalgia, consider alternative etiologies including concurrent statins or other myotoxic drugs, underlying inflammatory conditions, or other herbal supplements rather than attributing symptoms to saw palmetto. 6
Red yeast rice (containing lovastatin), wormwood oil, licorice, creatine monohydrate, and Hydroxycut are known causes of drug-induced rhabdomyolysis and myositis, not saw palmetto. 6
When monitoring patients on oral minoxidil who also take saw palmetto, standard monitoring for blood pressure, heart rate, and volume status should continue, with additional attention to bleeding manifestations if the patient is on antiplatelet agents or anticoagulants. 9