The human evidence on saw palmetto and hair is small and mostly uncontrolled. One two year open label study found that 38 percent of men taking saw palmetto improved on a photographic score. The only placebo controlled trial had ten men on the active blend. A 2020 systematic review of five randomised trials and two cohort studies concluded that "robust high-quality data are lacking". Saw palmetto carries no authorised health claim for hair in Great Britain. Below is what each named study reported, in its own numbers, with the design limits the authors themselves state.
Does saw palmetto help hair?
| Question | What the sources say | Source |
|---|---|---|
| What did the longest trial find? | In an open label two year study of 100 men, 38 percent of those on Serenoa repens 320 mg a day had an increase in hair growth on a photographic score index. | Rossi and colleagues, 2012 |
| Has a topical form been tested? | A 24 week pilot in 50 men with no placebo group reported higher average and terminal hair counts at weeks 12 and 24 than at baseline. | Wessagowit and colleagues, 2016 |
| Is there a placebo controlled trial? | A small double blind pilot of a blend of Serenoa repens extract and beta-sitosterol: 60 percent (6 of 10) on the active formulation were rated improved. Duration not stated in the abstract. | Prager and colleagues, 2002 |
| What does the systematic review conclude? | Five randomised trials and two cohort studies showed positive effects; saw palmetto was well tolerated; large trials isolating saw palmetto are needed. | Evron and colleagues, 2020 |
| Does saw palmetto hold a UK health claim for hair? | No. Only authorised claims in the Great Britain register may be used, and saw palmetto has none. | GB nutrition and health claims register |
Does saw palmetto work for women's hair?
The three trials described in this article enrolled men only. The 2020 systematic review covered patients with androgenetic alopecia and telogen effluvium without a separate result for women in its abstract. There is no authorised claim for saw palmetto for anyone in Great Britain.
Saw palmetto hair loss studies, one by one
Saw palmetto is an extract of Serenoa repens. The papers below state their own reasons for studying it; those are the authors' background statements and not a claim any UK supplement may make.
Rossi 2012: the two year open label study
Rossi and colleagues, in the International Journal of Immunopathology and Pharmacology, enrolled 100 men with clinically diagnosed mild to moderate androgenetic alopecia. One group received Serenoa repens 320 mg every day for 24 months; the other received the comparator medicine, 1 mg every day, for the same period. Efficacy was assessed with a score index comparing global photographs taken at the start and at 24 months. The authors report that "only 38% of patients treated with Serenoa repens had an increase in hair growth", against 68% on the comparator, and that the comparator was more effective for 33 of 50 patients with level II and III alopecia, and that Serenoa repens acted "prevalently in the vertex". Their summary of the Serenoa repens arm: it "could lead to an improvement of androgenetic alopecia".
Three design points. The abstract describes this as an open label study, so participants and investigators knew which treatment was given. The outcome was a score index based on comparing global photographs, not a hair count. The comparator result appears here only because it is part of the published trial; questions about prescription medicines belong with a GP.
Wessagowit 2016: the topical pilot
Wessagowit and colleagues, in the Australasian Journal of Dermatology, ran what they describe as "a pilot, prospective, open, within-subject comparison limited to 24 weeks using no placebo controls". Fifty male volunteers aged 20 to 50 received topical Serenoa repens products for 24 weeks. The primary end point was a hair count in an area of 2.54 square centimetres at week 24. The average hair count and terminal hair count increased at weeks 12 and 24 compared with baseline; the authors note that some of these results "levelled off at week 24, presumably because the concentrated topical product containing S. repens extract was stopped after 4 weeks". Patients were satisfied and side effects were limited. The authors' conclusion concerns topical use in men and carries the caveat that continued use of the concentrated product "may be necessary for sustained efficacy". With no placebo group and an open design, this is a pilot signal, not proof.
Prager 2002: the placebo controlled pilot of a blend
Prager and colleagues, in the Journal of Alternative and Complementary Medicine, describe "the first example of a placebo-controlled, double-blind study" of botanically derived compounds in androgenetic alopecia. The formulation tested was the liposterolic extract of Serenoa repens together with beta-sitosterol, in men aged 23 to 64 in good health with mild to moderate androgenetic alopecia. The blinded investigative staff rated 60 percent (6 of 10) of the subjects on the active formulation as improved at the final visit. The authors describe the result as justifying "the expansion to larger trials". Two limits follow directly from the abstract: the active group numbered ten, and the product was a blend, so the result cannot be assigned to saw palmetto on its own. An erratum to the paper was published in 2006.
Evron 2020: the systematic review
Evron and colleagues, in Skin Appendage Disorders, searched PubMed, Google Scholar and the Cochrane database for studies of supplements containing saw palmetto in alopecia. They found five randomised clinical trials and two prospective cohort studies, covering topical and oral supplements at 100 to 320 mg, in patients with androgenetic alopecia and telogen effluvium. Across those studies they report "sixty percent improvement in overall hair quality, 27% improvement in total haircount, increased hair density in 83.3% of patients, and stabilized disease progression among 52%" with the use of "various topical and oral SP-containing supplements". Saw palmetto "was well tolerated and not associated with serious adverse events in alopecia patients". Their conclusion: "Although robust high-quality data are lacking, supplements containing SP may be a treatment option", and "further large-scale RCTs focusing on the sole contribution of SP to hair growth outcomes are needed to confirm efficacy and determine long-term adverse events".
The review's percentages describe different outcomes in different studies with different formulations. They are not a single pooled result. The review describes the products as "supplements containing SP" and asks for trials on its "sole contribution", so the ingredient itself has not been isolated.
What are the limits of this evidence?
The abstracts state most of them. Two of the three trials (Rossi, Wessagowit) were open label. Only one was placebo controlled, and it tested a blend with ten men on the active arm. Durations were 24 weeks in one study, two years in another, and not stated in the third abstract. The outcome measures differ from study to study: photographic scores, hair counts in a marked area, investigator ratings, patient satisfaction. All three trials enrolled men only. Two of the three call themselves pilots, and the review says robust high quality data are lacking.
What did the studies report on side effects?
The systematic review reported saw palmetto as well tolerated and "not associated with serious adverse events in alopecia patients", and the topical pilot reported limited side effects. The Rossi and Prager abstracts say nothing on tolerability. The review also asks for trials that "determine long-term adverse events", so the long term picture is not settled. As with any supplement, speak to your GP before starting if you are pregnant, breastfeeding, taking medication or have a health condition.
Where this leaves saw palmetto in the UK
No health claim for saw palmetto is authorised in Great Britain, so no UK supplement may tell you what it will do for your hair. Dense includes saw palmetto in Daily Densify as a formulation choice and makes no claim for it; the science page states that saw palmetto carries no authorised claim and is included as a formulation choice. The studies above are studies of the ingredient in the settings described, not studies of Daily Densify. See also our UK guide to choosing hair vitamins and our pumpkin seed evidence review.
Frequently asked questions
Does saw palmetto help hair growth?
The human evidence is small and mostly uncontrolled. A two year open label study of 100 men reported that 38 percent of those taking Serenoa repens 320 mg a day had an increase in hair growth on a photographic score. The only placebo controlled trial had ten men on the active blend, and 6 of them were rated improved. The 2020 systematic review found positive effects across five randomised trials and two cohort studies but asks for large trials that isolate saw palmetto.
How long did the saw palmetto studies run?
The Rossi study ran for 24 months and measured at the start and end. The Wessagowit topical pilot ran for 24 weeks and measured at weeks 12 and 24. The Prager pilot's duration is not stated in its abstract. None of these durations is a guide to what any individual should expect.
What did the 2020 systematic review find?
Evron and colleagues found five randomised clinical trials and two prospective cohort studies of supplements containing saw palmetto, at 100 to 320 mg, in androgenetic alopecia and telogen effluvium. They report positive effects on hair quality, hair count, density and progression across those studies, well tolerated, and conclude that robust high quality data are lacking.
Does saw palmetto have side effects?
The systematic review reported saw palmetto as well tolerated and not associated with serious adverse events in alopecia patients, and the topical pilot reported limited side effects. The Rossi and Prager abstracts say nothing on tolerability, and the review asks for trials that determine long term adverse events.
Can a UK supplement claim saw palmetto helps hair?
No. Only authorised claims in the Great Britain nutrition and health claims register may be used, and saw palmetto has none.
Sources
- 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):1167-73.
- 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):e76-82.
- Prager N, Bickett K, French N, Marcovici G. A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia. J Altern Complement Med. 2002;8(2):143-52. Erratum 2006;12(2):199.
- Evron E, Juhasz M, Babadjouni A, Mesinkovska NA. Natural Hair Supplement: Friend or Foe? Saw Palmetto, a Systematic Review in Alopecia. Skin Appendage Disord. 2020;6(6):329-337.
- Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register.
Last updated: 6 September 2026. Written by the Dense editorial team and checked against the PubMed abstracts linked above on that date. This article is for information only and is not medical advice. If you are concerned about hair thinning or shedding, speak to a GP.
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