Hyaluronic Acid (Sodium Hyaluronate) for Skin Aging
Oral hyaluronic acid supplements show small, short-term gains in skin hydration and wrinkle depth in trials, but the evidence is weak: studies are small and almost all funded by manufacturers, and no major health authority endorses these skin claims.
Why this grade7-layer evidence engine
Six human studies underpin this rating. A 2025 meta-analysis (PMID 40911749) pooling roughly seven trials found statistically significant improvements in skin hydration, elasticity, and wrinkle depth, though firmness, wrinkle volume, and water loss (TEWL) did not reach significance. Individual placebo-controlled RCTs at 60-200 mg/day (PMID 41422283, n=150; PMID 34203487, n=40; PMID 28761365, n=60; PMID 34933842, n=60) reported similar short-term benefits, and an uncontrolled cohort (PMID 29228816, n=20) had no placebo arm.
The grade is capped at weak for concrete reasons. Sample sizes are small, trials run 12 weeks or less so durability is unknown, and nearly all positive studies were run or funded by manufacturers (e.g., Kewpie, Contipro), a serious conflict-of-interest signal. The evidence also covers oral capsules only — separate from topical serums and injectable dermal fillers, which consumers often conflate.
Regulators and clinics add caution rather than support. The US FDA halted a GRAS review of oral sodium hyaluronate, partly over possible "drug-like effects," and EU EFSA has authorized no skin health claims for it. Mayo Clinic discusses hyaluronic acid only as injectable fillers, not oral supplements, and the NIH, Harvard, and other major bodies do not address the oral skin claim — institutional silence that, alongside heavy affiliate marketing, warrants a cautious read.
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 = 0.594
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 無高階證據可裁決
- 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 + 1 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status