Vitamin E for Alzheimer
Verdict: Published with Warning
Across 6 PubMed studies, the evidence for Vitamin E in Alzheimer grades Tier C — weak evidence. Effective, but with safety or population caveats.
C 🟠 C Weak Evidence Published with Warning
Why this grade7-layer evidence engine
⚖️
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditableRaw score 0.45
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
C · Published with Warning
Confidence
86%
Highly consistent evidence
Evidence level
E1
Cochrane high-quality SR/MA
▸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 — 高品質 SR/MA 顯示 negative 主導 (3 negative > 0 positive)，下層 RCT 不能推翻
- apply_hec_override — HEC-1 高階證據 negative — 強制由 C 改為 D
- 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
PubMed studies (6)L2 · primary research & systematic reviews
Vitamin E for Alzheimer's dementia and mild cognitive impairment
Finding: Across 4 RCTs (usable data from one AD trial n=304 and one MCI trial n=516), there was no clinically important effect on cognition and no effect on MCI-to-dementia progression; only moderate-quality evidence from a single AD trial that alpha-tocopherol slowed functional decline (ADCS-ADL), with no increase in mortality or serious adverse events.
View on PubMed Effect of vitamin E and memantine on functional decline in Alzheimer disease: the TEAM-AD VA cooperative randomized trial
Finding: Alpha-tocopherol 2000 IU/day slowed functional decline by 3.15 ADCS-ADL units versus placebo (95% CI 0.92 to 5.39; adjusted P=.03), equivalent to a 19% slower annual progression or ~6.2-month delay; memantine and the combination showed no benefit on the primary outcome.
View on PubMed A controlled trial of selegiline, alpha-tocopherol, or both as treatment for Alzheimer's disease (Alzheimer's Disease Cooperative Study)
Finding: Alpha-tocopherol 2000 IU/day delayed the composite primary endpoint (median 670 vs 440 days; P=.001 after adjustment for baseline MMSE), but there was no improvement in cognitive test scores; benefit was on functional/clinical milestones only, not cognition.
View on PubMed Association of Antioxidant Supplement Use and Dementia in the Prevention of Alzheimer's Disease by Vitamin E and Selenium Trial (PREADViSE)
Finding: Dementia incidence (325/7338 men, 4.4%) did not differ across arms; vitamin E vs placebo hazard ratio was 0.88 (95% CI 0.64-1.20), non-significant — neither vitamin E nor selenium prevented dementia.
View on PubMed Effects of vitamin E supplementation on the risk and progression of AD: a systematic review and meta-analysis
Finding: Pooled estimate showed no statistically significant effect of vitamin E on AD risk/progression (RR 0.81, 95% CI 0.50-1.33), with the confidence interval crossing 1.0.
View on PubMed Association of antioxidants intake in diet and supplements with risk of Alzheimer's disease: a systematic review and dose-response meta-analysis of prospective cohort studies
Finding: This recent dose-response meta-analysis found no clear protective association between vitamin E intake (diet or supplements) and Alzheimer's disease risk, consistent with the null prevention picture from RCTs.
View on PubMed Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …
L4a US FDA
Cautious
Some scientific evidence suggests that consumption of antioxidant vitamins may reduce the risk of certain forms of cancer. However, FDA has determined that this evidence is limited and not conclusive. source↗
L4b EU EFSA
Cautious
The effect on blood clotting and associated increased risk of bleeding is considered as the critical effect to establish an UL for vitamin E. ... The ULs for vitamin E from all dietary sources, which were previously established by the Scientific Committee on Food, are retained for all population groups source↗
L4c UK NHS
Cautious
You should be able to get all the vitamin E you need from your diet. Taking 540mg (800 IU) or less a day of vitamin E supplements is unlikely to cause any harm. If you take vitamin E supplements, do not take too much as this could be harmful. source↗
L4d TW TFDA / 衛福部
Cautious
其維生素E之總含量不得高於400I.U.（268mg d-α-tocopherol） source↗
L4e WHO
Cautious
Vitamin E and C supplementation is not recommended for pregnant women to improve maternal and perinatal outcomes. source↗
L5a NIH Office of Dietary Supplements
Cautious
Clinical trials have not provided evidence that routine use of vitamin E supplements prevents cardiovascular disease or reduces its morbidity and mortality. source↗
L5b Mayo Clinic
Cautious
If you've been diagnosed with mild to moderate Alzheimer's disease, some research suggests that vitamin E therapy might help slow the worsening of the disease. However, some research shows that high-dose vitamin E might slow mild to moderate Alzheimer's disease, while other studies don't show this. Vitamin E supplements appear to have no effect on whether people with mild cognitive impairment g… source↗
L5c Cleveland Clinic
Cautious
In people who already have dementia, a daily supplement of vitamin E may slow the rate of decline. High doses of vitamin E supplements are associated with an increased risk of death. source↗
L5d Harvard Health
Cautious
only high doses of vitamin E have been shown to modestly help people who already have moderate dementia. The only convincing evidence for a benefit of vitamin E (for people with moderate Alzheimer's disease) comes from a study involving a relatively high dose: 2,000 IU per day. Vitamin E at doses higher than 400 international units (IU) per day is risky for people with active cardiovascular dis… source↗
L5e Specialty Society (condition-mapped)
Cautious
In patients with mild cognitive impairment, the AAN recommends regular exercise and no drugs or supplements. The Alzheimer's Association states that not a single food, beverage, ingredient, vitamin or supplement has been proven to prevent, treat or cure Alzheimer's disease or to benefit cognitive function or brain health. source↗