Vitamin A for Acne
There is no credible evidence that oral vitamin A (retinol or beta-carotene) supplements treat acne. The acne-fighting "vitamin A" people read about refers to prescription retinoid drugs, not the dietary supplement.
Why this grade7-layer evidence engine
The direct evidence on the supplement is thin and points the wrong way. Only two small case-control studies actually measured vitamin A in acne patients (El-Akawi 2006, n=200, PMID 16681594; Ozuguz 2014, n=188, PMID 23826827), and both merely found that people with acne tend to have lower serum retinol. That is a correlation, not proof that taking vitamin A clears acne. No modern randomized trial supports oral retinol or beta-carotene as an acne therapy.
Authorities are consistent in not endorsing it. The Mayo Clinic states plainly that 'large doses of oral vitamin A supplements don't seem to affect acne,' and the AAD's 2024 acne guideline (PMID 38300170) found evidence 'insufficient' to recommend vitamins or other dietary changes. Cleveland Clinic and Harvard Health discuss only prescription retinoids. The effective acne treatments are vitamin A *derivatives* regulated as drugs (topical tretinoin/adapalene, oral isotretinoin), which are pharmacologically distinct from the supplement.
The historic high-dose route is a dead end, not a loophole. A review of diet and acne (PMID 24719062) notes that mid-century case series used 300,000-500,000 IU/day of retinol, doses 30-50 times the upper limit that cause liver toxicity and birth defects, which is precisely why isotretinoin replaced them in 1982. Doses high enough to plausibly affect the skin are toxic; doses within safe limits show no benefit. Pregnant women should avoid retinol supplements entirely.
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 = 0.302
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 僅有 E10 級證據 (cohort/animal/mechanism)，不足以下結論
- tier_strict_requirement_check — D 級條件未達 (需 E1-E3 negative；實際 E10)
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status