Evidence Trace, complete trial record
In plain terms
In plain terms: Vitamin E (supplemental alpha-tocopherol) has been tested in human trials aimed at the relevant outcome and did not show benefit at the doses and durations studied. The animal research may be encouraging, but it has not yet translated to humans in these trials.
Vitamin E (supplemental alpha-tocopherol)
D
Not shown: no human trial shows benefit
Route 2 — tested in humans; benefit not shown
The endpoint this grade is based on: Hard clinical endpoint (mortality, major event), Tested at scale for cancer prevention with no benefit in any large trial. In SELECT, 400 IU/day of synthetic vitamin E significantly increased prostate cancer in healthy men on extended follow-up; a second large trial in healthy men at 400 IU every other day found no prostate effect either way.
The evidence as the record states it
SELECT, Lippman et al. (JAMA, 2009; PMID 19066370): 35,533 healthy men, 400 IU/day all rac-alpha-tocopheryl acetate; no prevention of prostate or any prespecified cancer, with a nonsignificant prostate cancer increase (P=0.06). SELECT, Klein et al. (JAMA, 2011; PMID 21990298): extended follow-up through July 2011, after supplements were stopped in October 2008; prostate cancer increased significantly (hazard ratio 1.17, 99% CI 1.004 to 1.36, P=0.008), 1.6 more cases per 1,000 person-years. Physicians' Health Study II, Gaziano et al. (JAMA, 2009; PMID 19066368): 14,641 male physicians, 400 IU synthetic vitamin E every other day for a mean 8 years; prostate cancer hazard ratio 0.97 and total cancer unchanged. Women's Health Study, Lee et al. (JAMA, 2005; PMID 15998891): 39,876 women, 600 IU natural vitamin E on alternate days for 10 years; no effect on total cancer or major cardiovascular events. HOPE-TOO, Lonn et al. (JAMA, 2005; PMID 15769967): 400 IU/day natural vitamin E in people with vascular disease or diabetes; no effect on cancer incidence or death, higher heart failure (RR 1.13) and heart failure hospitalization. O'Connor et al. (JAMA, 2022; PMID 35727272), USPSTF evidence review: vitamin E not associated with cancer incidence (5 trials) or mortality (9 trials); hemorrhagic stroke flagged as a possible serious harm. Loh et al. (Stroke Vasc Neurol, 2021; PMID 33109618): 18 trials, hemorrhagic stroke RR 1.17 (0.98 to 1.39), ischemic stroke slightly lower. Alpha-Tocopherol Beta-Carotene (ATBC) Study Group, group-authored (New England Journal of Medicine, 1994; PMID 8127329): 29,133 male smokers, 50 mg/day, a different dose and population; no reduction in lung cancer, fewer prostate cancers, more deaths from hemorrhagic stroke. D Route 2: tested, no benefit in any large trial, with a prostate cancer harm in SELECT.
PMID 21990298 PMID 8127329 PMID 19066368 PMID 19066370 PMID 35727272 PMID 15769967 PMID 15998891 PMID 33109618
Trials showing no benefit
- Endpoint
- Prostate cancer incidence
- Population
- Healthy men, 400 IU/day all rac-alpha-tocopheryl acetate, planned 7-12 year follow-up
Observation
High. Large randomized placebo-controlled trial. Supplementation SIGNIFICANTLY INCREASED prostate cancer risk.
Evidence by specific use
Major cardiovascular events
Grade D
HOPE (Yusuf et al., N Engl J Med, 2000; PMID 10639540): 9,541 people aged 55 and over with vascular disease or diabetes, 400 IU a day of natural vitamin E for a mean 4.5 years; primary events 16.2 against 15.5 percent (relative risk 1.05, 0.95 to 1.16). Physicians' Health Study II (Sesso et al., JAMA, 2008; PMID 18997197): 14,641 men, 400 IU every other day for a mean 8 years; major cardiovascular events unchanged (hazard ratio 1.01, 0.90 to 1.13). Women's Health Study (Lee et al., JAMA, 2005; PMID 15998891): 39,876 women, 600 IU on alternate days for 10 years; major events not significantly changed (relative risk 0.93, 0.82 to 1.05), with fewer cardiovascular deaths (0.76) as a secondary finding. Three large trials, none lowering major cardiovascular events: tested, no benefit.
PMID 10639540 PMID 18997197 PMID 15998891
Why Grade D Route 2 and not Grade C
Grade D Route 2 applies when a compound has been tested in humans and benefit was not shown. Vitamin E (supplemental alpha-tocopherol) has been tested in 1 human trial on endpoints relevant to the claim being evaluated, and the primary endpoint was not met.
A randomized, placebo-controlled trial pre-specifying a meaningful clinical or functional endpoint and demonstrating statistically significant benefit would move this to Grade C or higher, depending on effect size, population size, and whether it is independently replicated.
What this grade covers and what it does not
Grade D on Route 2: tested, harm found. Every large randomized trial of supplemental vitamin E for cancer prevention found no benefit: SELECT (PMID 19066370; PMID 21990298), the Physicians' Health Study II (Gaziano et al., 2009; PMID 19066368; 14,641 men, 400 IU every other day, prostate cancer hazard ratio 0.97), the Women's Health Study (Lee et al., 2005; PMID 15998891; 600 IU of natural vitamin E on alternate days), HOPE-TOO (Lonn et al., 2005; PMID 15769967; 400 IU/day natural vitamin E in vascular disease or diabetes), and the USPSTF pooling of 5 trials (O'Connor et al., 2022; PMID 35727272; cancer incidence odds ratio 1.02). Replicated no-benefit is what makes the D solid. The harm badge rests on SELECT: 400 IU/day of synthetic all rac-alpha-tocopheryl acetate in 35,533 healthy men raised prostate cancer significantly on extended follow-up (hazard ratio 1.17, P=0.008, Klein et al., 2011; PMID 21990298). The primary 2009 report had shown a nonsignificant increase (P=0.06), the extended follow-up ran past the date participants stopped their supplements in October 2008, and PHS II did not reproduce the increase at its every-other-day dose. ATBC (PMID 8127329) tested 50 mg/day in male smokers, a different dose and population, and saw fewer prostate cancers; it does not test this use. Other harms in the trials: higher heart failure in HOPE-TOO (relative risk 1.13), and a hemorrhagic stroke signal flagged by the USPSTF review and in pooled trials (Loh et al., 2021; PMID 33109618; RR 1.17, not significant). WHAT THIS GRADE DOES NOT COVER: vitamin E from food, mixed tocopherol and tocotrienol preparations, correction of a documented deficiency, or vitamin E studied in a diagnosed condition such as nonalcoholic steatohepatitis, where the trials and the answer are different and are not summarized here.
What would move this grade
A randomized, placebo-controlled trial pre-specifying a clinical aging endpoint and demonstrating statistically significant benefit on that primary endpoint would be sufficient to move this to Grade C or higher, depending on effect size and population.
How to track whether this is working
No validated human outcome to track.