Supplements

Saw Palmetto

Updated · 24 sources · Editorial policy

Saw palmetto is an extract of the berries of Serenoa repens, a small palm native to the southeastern United States. It is sold as a dietary supplement for urinary symptoms from an enlarged prostate (benign prostatic hyperplasia, BPH) and for male pattern hair loss, often as a “natural DHT blocker” and an alternative to finasteride or dutasteride.

The single most important fact is that large, well-run trials found it no better than placebo for prostate symptoms. Two NIH-funded trials, STEP and CAMUS, were null, and the 2023 Cochrane review concluded that saw palmetto alone gives little to no benefit for BPH symptoms (Franco et al., Cochrane 2023). The hair loss evidence consists of a few small trials, most testing combination or proprietary products.

This page summarizes what the clinical trials, systematic reviews and regulators report. It is for education only and is not medical advice.

Property Detail
Type Herbal extract of the fruit of Serenoa repens (also called Sabal serrulata)
Main constituents About 90% fatty acids, mostly free fatty acids (oleic and lauric acid are the largest share), in the hexane extract Permixon
Route Oral; topical products in some hair loss studies
Studied doses 320 mg/day (160 mg twice daily) is the standard trial dose; CAMUS tested up to 960 mg/day
Half-life Not established; the EU herbal monograph lists no pharmacokinetic data
Proposed mechanism Inhibits both 5α-reductase types in cell and enzyme studies; did not lower serum DHT in a 1-week study in healthy men
US status Dietary supplement; not FDA-approved for any condition
EU status Hexane extract accepted for BPH symptoms (“well-established use”); ethanol extract as a traditional herbal medicine
BPH evidence Little to no benefit over placebo (Cochrane 2023, high-certainty evidence)

What it is

Saw palmetto preparations are made by extracting the dried ripe berries with a solvent, which is then partly evaporated to leave a soft, oily extract. The European Medicines Agency (EMA) describes two types: extracts made with hexane and extracts made with ethanol (EMA, saw palmetto fruit summary). Supplements also use extracts made with supercritical carbon dioxide (CO₂), such as the product tested in the STEP trial (Barry et al., JAMA 2011).

The extract is mainly fat. The best-studied hexane extract, Permixon, is about 90% fatty acids, 80% of them in free (unbound) form (Raynaud et al., J Steroid Biochem Mol Biol 2002). Oleic and lauric acid make up about 65% of the free fatty acids, and linoleic and myristic acid another 15%. The EU monograph’s hexane extract contains 92% fatty acids and 2% of an unsaponifiable (non-fatty) part, which includes plant sterols (EU herbal monograph, EMA 2015).

The proposed 5α-reductase mechanism

5α-reductase is the enzyme that converts testosterone into dihydrotestosterone (DHT), a stronger androgen that drives prostate growth and male pattern hair loss. The theory behind saw palmetto is that it blocks this enzyme, as finasteride and dutasteride do.

The laboratory evidence for this comes from cell and enzyme studies:

  • Both enzyme types (in vitro). Using the cloned human type 1 and type 2 enzymes expressed in insect cells, Permixon blocked both. Only the free fatty acids were active; esterified fatty acids, alcohols and sterols were not (Raynaud et al., 2002).
  • Potency differs by fatty acid (in vitro). Lauric acid inhibited both types at similar concentrations (IC50, the concentration giving half-maximal inhibition, 17 and 19 µg/mL). Oleic acid acted mainly on type 1 (IC50 4 µg/mL vs over 100 µg/mL for type 2).

The EMA’s assessment states that the mechanism of action is not known, and that the laboratory work suggests it reduces the action of male sex hormones and may have anti-inflammatory effects (EMA summary).

How it compares with finasteride and dutasteride

The key difference is that the drugs have shown large, reproducible drops in serum DHT in humans. Saw palmetto has not shown this consistently.

Measure Saw palmetto Finasteride Dutasteride
Enzyme target Types 1 and 2 in cell and enzyme studies Selective for type 2 Types 1 and 2
Serum DHT, healthy men, 1 week No effect, same as placebo (320 mg/day) −52% to −65% (5 mg/day) Not tested in this study
Serum DHT, men with BPH, 24 weeks Not tested −70.8% (5 mg/day) −94.7% (0.5 mg/day)

Sources: Strauch et al., Eur Urol 1994; Clark et al., JCEM 2004.

For the drugs’ clinical trial results, labeled uses and side effects, see the finasteride and dutasteride pages.

How it works in the body

Little is known about how saw palmetto is absorbed or cleared. The EU herbal monograph lists “no data available” for pharmacokinetics, and no half-life has been established (EU herbal monograph). Because the extract is a mixture of many fatty acids and sterols, there is no single compound whose blood levels define a dose.

Effects on testosterone and DHT

Human hormone data are limited and partly conflicting:

Study Design and n Product and dose Hormone finding
Strauch et al., Eur Urol 1994 Open, randomized, placebo-controlled; 32 healthy men aged 20–30; 1 week Permixon 160 mg twice daily No effect on serum DHT (same as placebo); finasteride 5 mg cut DHT 52–65%. Serum testosterone stayed in the normal range in all groups.
Di Silverio et al., Prostate 1998 Prostate tissue from treated vs untreated men with BPH Permixon 320 mg/day for 3 months In the periurethral region, tissue DHT was lower (2,363 vs 7,317 pg/g) and tissue testosterone higher (1,023 vs 615 pg/g)
Sudeep et al., Clin Cosmet Investig Dermatol 2023 Double-blind, placebo-controlled, 4 arms, 80 adults with hair loss; 16 weeks Proprietary saw palmetto oil, 400 mg/day oral Serum DHT 1.29-fold lower than baseline in the oral group (p under 0.001 vs placebo); no change with the topical form

The tissue study suggests some 5α-reductase inhibition inside the prostate, the pattern expected from this class of drug. However, it was not a randomized comparison. The 2023 trial was run by employees of the company that makes the tested product.

In men with BPH, saw palmetto did not change prostate-specific antigen (PSA), a protein made by the prostate. In CAMUS, PSA changed by a mean of +0.23 ng/mL on saw palmetto vs +0.16 ng/mL on placebo over 72 weeks (p = 0.50), even at 960 mg/day (Andriole et al., J Urol 2013). STEP also found no PSA difference (Bent et al., NEJM 2006).

Regulatory status

  • United States. Saw palmetto is sold as a dietary supplement. Dietary supplements are not approved by the FDA before they are sold, and manufacturers are responsible for their safety and labeling (NCCIH).
  • European Union. The EMA’s herbal committee (HMPC) accepted the hexane extract for the “symptomatic treatment of benign prostatic hyperplasia” as a well-established use, at 320 mg once daily or 160 mg twice daily. It accepted the ethanol extract (320 mg once daily) only as a traditional herbal medicine for urinary symptoms, based on long use rather than trial evidence. Both are for adult men only (EU herbal monograph). The monograph dates from 2015, before the 2023 Cochrane update.

What the research shows

Prostate symptoms (BPH)

Early studies looked positive. A 1998 meta-analysis of 18 randomized trials (2,939 men) found modest gains over placebo in symptoms and urine flow, and similar results to finasteride in two trials (Wilt et al., JAMA 1998). The authors noted that the trials were short (mean 9 weeks) and used varied products and outcome measures.

Larger and longer trials then failed to confirm a benefit:

Trial Design and n Dose and duration Main result
STEP (Bent et al., NEJM 2006) Double-blind RCT, 225 men over 49 with moderate to severe symptoms CO₂ extract 160 mg twice daily, 1 year No difference in AUA symptom score (mean difference 0.04 points; 95% CI −0.93 to 1.01) or peak urine flow (0.43 mL/min; 95% CI −0.52 to 1.38). No difference in prostate size, residual urine or PSA.
CAMUS (Barry et al., JAMA 2011) Double-blind RCT at 11 North American sites, 369 men aged 45 or older Ethanol extract 320 mg/day, raised to 640 then 960 mg/day; 72 weeks Symptom score fell 2.20 points on saw palmetto and 2.99 points on placebo; difference 0.79 points favoring placebo. No secondary outcome improved.

STEP and CAMUS together tested two extraction methods and up to three times the standard dose. Both were funded by the NIH. CAMUS used a standardized ethanol extract (85–95% fatty acids) donated by its manufacturer, which had no role in the analysis. In CAMUS, 42.6% of men on saw palmetto and 44.2% on placebo improved by at least 3 points.

The Cochrane reviews tracked this shift:

Review Trials and men Main finding
Tacklind et al., Cochrane 2012 32 RCTs, 5,666 men Not superior to placebo on AUA symptom score in the two high-quality long-term trials (MD 0.25 points; 95% CI −0.58 to 1.07); no gain in peak urine flow or prostate size
Franco et al., Cochrane 2023 27 RCTs, 4,656 men (placebo comparisons only) Little to no difference in IPSS at 3–6 months (MD −0.90 points on a 0–35 scale; 95% CI −1.74 to −0.07; high certainty) and at 12–17 months (MD 0.07; 95% CI −0.75 to 0.88)

The short-term difference of under 1 point is far smaller than the 3-point change used as the responder threshold in CAMUS. According to NCCIH, the Cochrane authors also analyzed hexane-extract studies separately and found no difference from other products (NCCIH). Combination products containing saw palmetto plus other herbs showed a larger effect (MD −2.41 points), but the certainty of that evidence was low.

Male pattern hair loss

Hair loss trials are few and small, and many test saw palmetto mixed with other ingredients. A 2020 systematic review found 5 randomized trials and 2 cohort studies, mostly of combination supplements, and concluded that robust high-quality data are lacking (Evron et al., Skin Appendage Disord 2020).

Study Design and n Product and duration Result
Prager et al., J Altern Complement Med 2002 Double-blind, placebo-controlled pilot in men with mild to moderate hair loss Saw palmetto extract combined with beta-sitosterol 6 of 10 men on the active product rated improved by blinded staff
Rossi et al., Int J Immunopathol Pharmacol 2012 Open-label comparison, 100 men; no placebo Saw palmetto 320 mg/day vs finasteride 1 mg/day, 24 months Hair growth improved in 38% on saw palmetto vs 68% on finasteride (photo scoring)
Wessagowit et al., Australas J Dermatol 2016 Open-label, no placebo, 50 men Topical saw palmetto products, 24 weeks Hair counts rose from baseline; some gains leveled off by week 24
Sudeep et al., 2023 Double-blind, placebo-controlled, 80 men and women (20 per arm) Proprietary oil 400 mg oral or 20% topical, 16 weeks Hair fall down up to 29% and hair density up 5.17% (oral) and 7.61% (topical) from baseline; manufacturer-run
Ablon, J Cosmet Dermatol 2026 Double-blind, placebo-controlled, 60 adults with self-perceived thinning (40 active, 20 placebo) Proprietary fatty acid extract, 160 mg/day, 180 days Terminal hair count +18.6 vs −10.1 on placebo (p under 0.001)

The only head-to-head study with finasteride favored finasteride, and it was open-label, so neither patients nor assessors were blinded. The placebo-controlled trials each tested a different proprietary product, with 10–40 people on active treatment. No large independent trial of saw palmetto alone for hair loss has been published. NCCIH states the evidence is too limited to allow conclusions (NCCIH).

Side effects and risks

Tolerability in trials

In controlled trials, side effects were similar to placebo:

  • Cochrane 2023. Adverse events probably differ little from placebo (RR 1.01; 95% CI 0.77 to 1.31; 12 studies, 2,399 men). That equals about 2 more events per 1,000 men (Franco et al., 2023).
  • CAMUS safety analysis. Among 357 men followed for 18 months on up to 960 mg/day, there were no significant differences in serious or non-serious adverse events, vital signs, lab tests or withdrawals, and no dose-response pattern (Avins et al., J Urol 2013).
  • Systematic review of adverse events. Across 40 articles (26 of them randomized trials), the most frequent complaints were abdominal pain, diarrhea, nausea, fatigue, headache, decreased libido and rhinitis. Isolated serious reports (including death and brain bleeding) had questionable causality (Agbabiaka et al., Drug Saf 2009).

The EU monograph lists abdominal pain and headache as common (1–10 in 100 users). Nausea, raised liver enzymes (transaminases or GGT), skin rash and reversible gynecomastia (breast tissue growth in men) are listed as uncommon (EU herbal monograph).

Persistent sexual and psychiatric symptoms

A 2026 Italian case series described sexual, psychiatric and physical symptoms after saw palmetto use, similar to reports of post-finasteride syndrome (Firenzuoli et al., Br J Clin Pharmacol 2026). Cases came from self-reports on an online forum and were then clinically evaluated. Reported doses were 120–900 mg/day. Symptoms lasted a mean of 4.7 years, and causality was rated “probable” in 54% of reports. A case series cannot show how often this happens or prove cause, but it challenges the assumption that the supplement has no hormonal side effects.

Interactions

  • Warfarin. The EU monograph notes a few suspected interactions with warfarin with raised INR (a measure of blood clotting time) (EU herbal monograph). The 2009 systematic review found no documented drug interactions (Agbabiaka et al., 2009).
  • PSA testing. Saw palmetto does not appear to change PSA readings, even at high doses (NCCIH; Andriole et al., 2013).

Who should not use it

  • Pregnancy and breastfeeding. NCCIH states saw palmetto may be unsafe in pregnancy or while breastfeeding (NCCIH). The EU monograph lists no relevant use in women, children or adolescents.
  • Hypersensitivity to the extract is the only contraindication in the EU monograph.
  • Worsening urinary symptoms. The monograph advises seeing a doctor if symptoms such as fever, blood in the urine, painful urination or urinary retention occur.
  • Missing data. Reproductive toxicity, genotoxicity and carcinogenicity tests have not been performed, and there are no fertility data.

Quality and extract variability

“Saw palmetto” on a label does not describe one product. Extracts differ in solvent (hexane, ethanol or CO₂), concentration and composition, and trial results for one extract may not apply to another.

  • Composition differs between brands. A chromatography study of 14 brands found significantly different proportions of free fatty acids, esters and glycerides. The authors argued that each brand should be judged on its own data (Habib and Wyllie, Prostate Cancer Prostatic Dis 2004).
  • Label claims are often wrong. In an analysis of 6 saw palmetto supplements, measured content ranged from 97% below to 140% above the labeled dose. Three contained under 20% of the stated amount, and one of two brands tested differed significantly between lots (Feifer et al., J Urol 2002).
  • Trials used defined products. CAMUS used an extract standardized to a reference chromatogram, and the EU monograph defines the extraction solvent and ratio. Typical retail supplements are not held to these specifications.

The variability argument cuts both ways. It may explain inconsistent results between small trials. However, the well-characterized extracts tested in STEP and CAMUS were also null, and the Cochrane analysis found no advantage for hexane extracts.

Key takeaways

  • No benefit for prostate symptoms in the best trials. STEP (225 men, 1 year) and CAMUS (369 men, up to 960 mg/day for 72 weeks) found no improvement over placebo. The 2023 Cochrane review rated the evidence of little to no benefit as high certainty.
  • Hair loss evidence is thin. The trials have 10–50 people per arm, often use combination or proprietary products, and include open-label designs. In the one comparison with finasteride, finasteride did better.
  • Not a proven DHT blocker in humans. It blocks 5α-reductase in lab studies, but it did not lower serum DHT in healthy men. Finasteride cut serum DHT by about 70% and dutasteride by about 95% in BPH trials.
  • Generally well tolerated. Side effect rates in trials were similar to placebo. The EU monograph lists abdominal pain and headache as common, and there are reports of warfarin interactions and of persistent sexual side effects.
  • Products vary widely. Composition differs between brands, and some tested supplements contained under 20% of the labeled amount.

Sources

  1. Franco JV, Trivisonno L, Sgarbossa NJ, et al. Serenoa repens for the treatment of lower urinary tract symptoms due to benign prostatic enlargement. Cochrane Database Syst Rev. 2023;6(6):CD001423. PubMed.
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  14. Rossi A, Mari E, Scarno M, et al. Comparitive effectiveness of finasteride vs Serenoa repens in male androgenetic alopecia: a two-year study. Int J Immunopathol Pharmacol. 2012;25(4):1167–1173. PubMed.
  15. Wessagowit V, Tangjaturonrusamee C, Kootiratrakarn T, et al. Treatment of male androgenetic alopecia with topical products containing Serenoa repens extract. Australas J Dermatol. 2016;57(3):e76–e82. PubMed.
  16. Sudeep HV, Rashmi S, Jestin TV, et al. Oral and topical administration of a standardized saw palmetto oil reduces hair fall and improves the hair growth in androgenetic alopecia subjects: a 16-week randomized, placebo-controlled study. Clin Cosmet Investig Dermatol. 2023;16:3251–3266. PubMed.
  17. Ablon G. The safety and efficacy of a novel saw palmetto (Serenoa repens) extract for promoting hair growth in adults with self-perceived thinning hair: 180-day results. J Cosmet Dermatol. 2026;25(2):e70717. PubMed.
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  24. National Center for Complementary and Integrative Health. Saw palmetto. NCCIH.