Saw Palmetto (Serenoa repens)

Overview

Saw palmetto (Serenoa repens) is a small, slow-growing palm native to the southeastern United States, whose berries are harvested for a lipid-rich extract. The primary purpose of this botanical supplement is to modulate androgen metabolism, a property that underlies most of its clinical use, especially for benign-prostatic-hyperplasia (BPH) and related urinary-tract symptoms.

Benefits

Benign-prostatic-hyperplasia (BPH): Meta-analyses of randomized controlled trials (RCTs) have shown that 160 mg daily of standardized saw-palmetto extract can reduce nocturnal urinary frequency and improve urine flow (average improvement 1–2 mL/s).
Androgen-related dermal conditions: Small trials indicate modest reductions in scalp sebum and modest improvement in mild androgenic alopecia when combined with other phytotherapeutics.
Lower urinary-tract symptoms (LUTS) in men: Consistent use for 6 months improves International Prostate Symptom Score (IPSS) by 3–4 points versus placebo.
Inflammatory modulation: In vitro and animal studies show inhibition of NF-κB and COX-2 pathways, suggesting potential benefits in chronic inflammatory states, though human data remain limited.
Metabolic health: Limited pilot data suggest modest improvement in insulin sensitivity in overweight men, but larger trials are needed.

How It Works

Saw-palmetto’s activity derives from a complex mixture of fatty acids (e.g., lauric, myristic, oleic), phytosterols (β-sitosterol, campesterol), and flavonoids. The key actions are:

5-α-reductase inhibition (type II) – reduces conversion of testosterone to dihydrotestosterone (DHT), the androgen most responsible for prostatic growth.
Androgen-receptor antagonism – sterols compete with DHT at the androgen-receptor binding site, diminishing downstream gene transcription.
Anti-inflammatory effect – suppression of NF-κB, COX-2, and prostaglandin-E2 synthesis reduces local pro-inflammatory cytokine production.
Apoptosis modulation – up-regulation of pro-apoptotic proteins (Bax) and down-regulation of anti-apoptotic Bcl-2 in prostate epithelial cells has been observed in vitro.
Collectively, these actions reduce prostatic tissue proliferation and inflammation, leading to symptom relief.

Dosage

Clinical research most commonly employs a standardized, 85-% fatty-acid–free extract at 160 mg daily, administered in one or two divided doses (e.g., 80 mg twice daily).

For BPH, 160 mg/day for at least 6 months is typical.
Some studies used 320 mg/day (split dosing) without increased adverse effects, but this is not a standard recommendation.
Food does not significantly affect absorption; however, taking the dose with a meal can reduce gastrointestinal irritation.
For men with mild LUTS, a lower 80–120 mg dose may be trialed.
In research on androgenic alopecia, 160 mg daily for 12 weeks has been used.
Dose adjustments should be made under clinical supervision in patients on anticoagulants or hormonal therapies.

Safety & Side Effects

Saw-palmetto is generally well-tolerated. Reported adverse events are mild and include: gastrointestinal upset (bloating, diarrhea), headache, and occasional dizziness. Contraindications include known hypersensitivity to the plant, and caution is advised in:

Women who are pregnant, lactating, or planning pregnancy – insufficient safety data.
Men with prostate cancer – because of its androgen-modulating effects.
Patients on anticoagulants (e.g., warfarin) or antiplatelet drugs – potential additive antiplatelet effect; monitor INR.
Hormonal therapies (e.g., testosterone replacement) – possible additive anti-androgenic effect.

Drug interactions: modest inhibition of CYP2C9 and CYP3A4 may affect drugs metabolized by these enzymes (e.g., warfarin, statins). Routine liver-function testing is not routinely required but may be considered in long-term use >12 months.

Chemistry

Saw-palmetto extract is a complex mixture; its major phytochemicals include:

β-Sitosterol (C₂₉H₅₀O) – a plant sterol with a sterol-type tetracyclic ring system and a side-chain alkyl group.
Stigmasterol (C₂₉H₄₈O) – similar sterol structure with a double bond at C22-C23.
Lauric, myristic, oleic, and palmitic acids (C₁₂–C₁₈ fatty acids) comprising the lipid fraction.
The commonly used standardized extract contains ≥ 85 % fatty-acid-free (i.e., sterol-rich) material, with a typical β-sitosterol content of 0.5–1 % (w/w).
The full extract is a mixture, not a single molecule, so a complete molecular formula does not exist; however, the predominant sterol (β-sitosterol) has the IUPAC name (3β,22E)-Stigmasta-5,22-dien-3-ol.

Sources & Quality

The raw material is harvested from wild-grown or cultivated Serenoa repens palms in Florida, Georgia, and the Gulf Coast of the United States. Berries are collected in late summer, dried, and then super-critical CO₂ or ethanol-based extraction methods are used to produce a standardized, fatty-acid-free extract. Super-critical CO₂ yields a high-purity sterol fraction with minimal solvent residues, considered the gold-standard for supplement quality.

Quality considerations:

Standardization to ≥ 85 % fatty-acid-free sterol content is required for clinical comparability.
Third-party testing (e.g., USP, NSF) for contaminants (heavy metals, pesticides) and verification of sterol content is essential.
Sustainability: Overharvesting has threatened wild populations; certified “sustainable harvest” or cultivated sources are preferred to ensure ecological integrity.

All statements are based on peer-reviewed literature up to 2024. Users should consult healthcare professionals before initiating any supplementation.