Saw Palmetto for Hair Loss
Saw palmetto shows a weak, modestly positive signal for androgenetic hair loss, but the evidence is thin and it is clearly less effective than finasteride. It is at best a second-line option, and there is essentially no good data for telogen effluvium.
Why this grade7-layer evidence engine
The grade is Weak Evidence because the human data is small, heterogeneous, and prone to bias. A systematic review (PMID 33313047, ~717 subjects across 11 studies) found roughly 60% of androgenetic-alopecia patients reported improved hair quality, but the authors stressed the evidence base is limited. The supporting trials are tiny: Prager 2002 (PMID 12006122, n=26) was an industry-funded study of a saw palmetto plus beta-sitosterol combination, so the effect cannot be pinned on saw palmetto alone, and two topical RCTs (PMID 38021422 and PMID 26010505, each n=50) showed only modest, short-term gains.
Crucially, the one head-to-head trial, Rossi 2012 (PMID 23298508), found saw palmetto improved hair in just 38% of men versus 68% on finasteride, and it was weakest at the crown. Mechanistic work (PMID 20300369) supports 5-alpha-reductase inhibition as plausible, but plausibility is not proof.
Regulators and clinics reinforce the caution. The NIH/NCCIH states the evidence for male-pattern hair loss is too limited to draw conclusions, the UK NHS notes saw palmetto performed no better than placebo for its main prostate use, and the FDA has not approved it as a drug. Combined with the scope caveat that almost no data exists for telogen effluvium, this lands the verdict at weak rather than solid.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.625
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (1 篇 > 0 negative)
- tier_strict_requirement_check — | B→C 因 scope.conflation_risk=true 且 L11 獨評較低 (B7-2 tier cap)
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status