Vitamin E for Cognitive Function
The evidence for vitamin E and cognition is weak and splits two ways: high-dose alpha-tocopherol may modestly slow the loss of daily-living function (not memory) in people already diagnosed with mild-to-moderate Alzheimer's disease, but it does NOT prevent dementia or preserve cognition in healthy adults or those with mild cognitive impairment. It is not a general "brain" supplement, and high doses carry real bleeding and safety risks.
Why this grade7-layer evidence engine
The grade reflects a genuine two-track divergence rather than a single body of evidence. In a treatment setting, two government-funded RCTs in established Alzheimer's disease found that 2000 IU/day alpha-tocopherol slowed functional decline: Sano 1997 (PMID 9110909, n=341, moderate AD) delayed the composite endpoint of death/institutionalization/loss of daily-living ability (adjusted HR ~0.47), and Dysken's 2014 TEAM-AD trial (PMID 24381967, n=613) slowed ADCS-ADL decline by 3.15 points/year. Crucially, neither improved cognitive scores (ADAS-Cog, MMSE) - vitamin E delayed loss of daily function, it did not reverse memory loss.
In a prevention setting, the same dose failed. Petersen's MCI trial (PMID 15829527, n=769) showed no reduction in progression to Alzheimer's over three years (HR 1.02), and the large Physicians' Health Study II (PMID 20157142, n=5,956 healthy older men) found no cognitive benefit. Both Cochrane reviews confirm the split: the 2012 synthesis (PMID 23152215) found no efficacy, and the 2017 update (PMID 28418065) softened only to a 'possible functional benefit in AD, no benefit in MCI or dementia prevention.'
Regulators and clinics are uniformly cautious, which holds the grade at weak. The FDA, EFSA, UK NHS, WHO and NIH ODS endorse no cognitive claim and stress getting vitamin E from diet, while Mayo, Cleveland Clinic and Harvard echo only a possible slowing of decline in existing dementia, not in healthy or MCI populations. High-dose use (>=400 IU/day) is tied to bleeding and hemorrhagic-stroke risk, anticoagulant interactions, and an all-cause mortality signal, so any treatment use should be clinician-supervised, not self-prescribed.
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 = 0.448
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高階證據未達主導 (0 positive vs 1 negative)，由 raw_score 決定
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status