Cohort studyindependent cross-checkabstract checked I-SUP-107 standard review
Multivitamins and death in 390,000 Americans
Multivitamin Use and Mortality Risk in 3 Prospective US Cohorts.
Overview
Loftfield E et al.. JAMA Netw Open 2024 · PMID 38922615 · DOI 10.1001/jamanetworkopen.2024.18729
People who took multivitamins did not live longer; their risk of death was about 4% higher, which may reflect who takes supplements rather than the pills.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
To see whether multivitamin users live longer.
- How was the study done?
Three large cohort studies combined.
- How many people, animals or samples were studied?
390,124 adults.
- What was actually found?
No survival benefit; slight 4% higher death risk.
- How large was the observed effect?
HR 1.04 (1.02-1.07).
- What do the results mean in everyday life?
Multivitamins do not help healthy people live longer.
- What are the study's limitations?
Observational; self-report.
- What does it say about Elawady's specific claim?
Supports C-SUP-01; only weakly relevant to the harm claim in C-SUP-06.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot prove that multivitamins cause harm.
Scientific in-depth review
1. Full reference
- Authors
- Loftfield E et al.
- Journal
- JAMA Netw Open
- Year
- 2024
- Identifier
- PMID 38922615 DOI 10.1001/jamanetworkopen.2024.18729 · PMC11208972
- 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: Intramural NIH HHS
2. Research question
Is multivitamin use associated with mortality, accounting for healthy-user bias and reverse causation?
3. Study design and population
- Study design
- Cohort study – Pooled analysis of 3 prospective cohorts (NIH-AARP, PLCO, Agricultural Health Study)
- Population
US adults without cancer or other chronic diseases at baseline
- Country
USA
- Period
Baseline 1993-2001; follow-up up to 27 years
- Sample size
390,124 participants; 164,762 deaths
- Inclusion and exclusion criteria
No history of cancer or other chronic diseases
4. Methods and endpoints
- Exposure / intervention
Self-reported multivitamin use (baseline and follow-up)
- Comparator
Non-users
- Endpoints
All-cause and cause-specific mortality
- Statistical methods
Multivariable Cox models; time-varying analyses
5. Actual results
- Results
Daily MV use not associated with lower mortality: multivariable HR 1.04 (1.02-1.07) in the first half and 1.04 (0.99-1.08) in the second half of follow-up; similar HRs for major causes of death.
- Absolute risks
not reported in abstract
- Authors' conclusion
MV use was not associated with a mortality benefit.
6. Strengths
- Very large
- Long follow-up
- Attention to healthy-user bias
7. Weaknesses
- Observational; self-reported exposure
- Residual confounding possible in either direction
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Observational exposure; confounding.
9. Assessment of the statistical interpretation
HR 1.04 is small; a slight excess could reflect reverse causation (ill people starting supplements); randomised data (COSMOS, PHS II) show no mortality effect.
10. Relevance to the specific claim
No mortality benefit of multivitamins in a very large cohort; the small positive HR resembles the Iowa signal but is much weaker.
11. Independent contrary findings
RCTs show no increase.
12. Transferability to Germany and Europe
Applicable.
13. Overall methodological judgement
Supports 'no benefit'; weak and non-causal evidence for 'harm'.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
None material.
15. Linked fact checks
- When popular oral supplements (calcium, beta-carotene, vitamin E, omega-3, multivitamins, glucosamine, selenium, vitamin A) were tested in large long-term placebo-controlled trials, most failed to deliver the promised prevention of disease. – Studies supporting the claim
- Multivitamins, iron, folic acid, B6, magnesium, zinc and copper supplements increase mortality, and folic acid (with B12) increases cancer. – Studies with mixed or unclear results