Randomised controlled trialindependent cross-checkabstract checked I-SUP-122 standard review

Vitamin E, selenium status and prostate cancer (SELECT)

Baseline selenium status and effects of selenium and vitamin e supplementation on prostate cancer risk.

Overview

Kristal AR et al.. J Natl Cancer Inst 2014 · PMID 24563519 · DOI 10.1093/jnci/djt456

Vitamin E pills raised prostate cancer risk mainly in men who had low selenium levels.

Does the study support the specific claim? Yes · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: To see whether selenium status changes supplement effects.
How was the study done?: Case-cohort analysis in a randomised trial.
How many people, animals or samples were studied?: 1,739 cases; 3,117 subcohort.
What was actually found?: Vitamin E increased prostate cancer in low-selenium men.
How large was the observed effect?: +63% total, +111% high-grade.
What do the results mean in everyday life?: High-dose vitamin E pills are not advisable for men.
What are the study's limitations?: Subgroup analysis.
What does it say about Elawady's specific claim?: Supports C-SUP-03.
Do the results apply to Germany and Europe?: Applicable.
What can explicitly not be concluded from this study?: Cannot prove the subgroup effect.

Authors: Kristal AR et al.
Journal: J Natl Cancer Inst
Year: 2014
Identifier: PMID 24563519 DOI 10.1093/jnci/djt456 · PMC3975165
Verification: verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: No COI statement in PubMed record; funding listed: NCI NIH HHS

Do effects of selenium and vitamin E on prostate cancer depend on baseline selenium status?

Study design: Randomised controlled trial – Case-cohort analysis within the SELECT randomised trial
Population: SELECT participants (men)
Country: North America (SELECT trial; sites not stated in abstract)
Period: SELECT trial period
Sample size: 1,739 prostate cancer cases (489 high-grade); random subcohort 3,117
Inclusion and exclusion criteria: SELECT case-cohort

Exposure / intervention: Selenium and/or vitamin E (400 IU/day) supplementation by baseline toenail selenium
Comparator: Placebo
Endpoints: Total, low-grade and high-grade prostate cancer
Statistical methods: Proportional hazards models within selenium quintiles

Results: Vitamin E alone had no effect in men with higher selenium status but increased total (63%, P=0.02), low-grade (46%, P=0.09) and high-grade (111%, P=0.008) prostate cancer in men with lower selenium status. Selenium increased high-grade prostate cancer by 91% (P=0.007) in men with higher selenium status.
Absolute risks: not reported in abstract
Authors' conclusion: Men should avoid selenium or vitamin E supplementation at doses exceeding recommended intakes.

Orienting tool: RoB 2
Type of assessment: simplified assessment (abstract only)
Full formal assessment: no
Overall risk of bias: some concerns
Rationale: Randomised comparison within subgroups; subgroup credibility moderate.

Subgroup findings; interaction not given in abstract.

Supports a prostate cancer hazard of high-dose vitamin E, concentrated in men with low selenium status.

Subgroup analysis; ATBC found fewer prostate cancers with low-dose vitamin E.

Applicable.

Supportive but subgroup-based.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	low
Directness	direct
Reproducibility	not replicated
Consistency with the overall evidence	mixed
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Replication.