Saw Palmetto: An Herbal Supplement for Prostate Health
Saw palmetto is an herbal supplement derived from the berries of the American dwarf palm tree (Serenoa repens) that is primarily used for urinary symptoms related to benign prostatic hyperplasia (BPH), though recent high-quality clinical trials have shown it is no more effective than placebo for this purpose.
What is Saw Palmetto?
Saw palmetto is one of the most commonly used herbal supplements for men with prostate-related urinary symptoms. It contains several bioactive compounds, including:
- Phytosterols (particularly beta-sitosterol)
- Fatty acids
- Flavonoids
Traditional and Current Uses
Saw palmetto extract has been widely used in Europe and the United States as a therapeutic remedy for:
- Lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH)
- Prostate health maintenance
- More recently, some studies have investigated its use for female urinary symptoms 1
Proposed Mechanisms of Action
Several mechanisms have been proposed for saw palmetto's effects:
- Inhibition of 5-alpha-reductase (similar to finasteride and dutasteride)
- Binding to pharmacologically relevant receptors in the lower urinary tract:
- Alpha-1 adrenoceptors
- Muscarinic cholinoceptors
- Vanilloid receptors 2
- Anti-inflammatory effects
- Potential anti-androgenic properties
Clinical Evidence and Efficacy
Despite its widespread use, high-quality clinical evidence does not support saw palmetto's effectiveness:
A rigorous randomized controlled trial published in JAMA (2011) found that even increasing doses of saw palmetto extract (up to 3 times the standard dose of 320 mg/day) did not reduce lower urinary tract symptoms more than placebo 3
An earlier New England Journal of Medicine study (2006) similarly found that saw palmetto did not improve symptoms or objective measures of BPH compared to placebo 4
Effect on PSA Testing
An important clinical consideration is saw palmetto's potential effect on PSA testing:
- According to NCCN guidelines, saw palmetto may contain phytoestrogenic compounds that can affect serum PSA levels 5
- This could potentially interfere with prostate cancer screening and monitoring
Safety and Drug Interactions
Saw palmetto is generally considered safe with minimal side effects, but there are important perioperative considerations:
- The Society for Perioperative Assessment and Quality Improvement (SPAQI) recommends holding saw palmetto for 2 weeks before surgery due to potential increased bleeding risk 5
- It may inhibit cyclooxygenase in animal models, potentially affecting platelet function 5
- Case reports have documented excessive bleeding in surgical patients taking saw palmetto 5
Important Clinical Considerations
- Patients taking 5-alpha reductase inhibitors (finasteride, dutasteride) for BPH should be aware that adding saw palmetto may not provide additional benefits
- Patients should disclose saw palmetto use before PSA testing, as it may affect results
- Healthcare providers should document saw palmetto use when interpreting PSA values, especially when calculating PSA doubling time 5
- Patients should discontinue saw palmetto at least 2 weeks before surgery due to potential bleeding risk
Recent Research Developments
Some newer research suggests potential benefits:
- A 2022 study found saw palmetto extract may help mitigate lower urinary tract symptoms in women, particularly daytime frequency and nocturia 1
- Some research suggests beta-sitosterol (a component of saw palmetto) may have anti-tumorigenic effects in prostate cancer cells, though clinical significance remains unclear 6
Despite these findings, the highest quality evidence from large randomized controlled trials does not support saw palmetto's efficacy for BPH symptoms.