Randomised controlled trialcited by the Tayebat archiveabstract only checked A-SUP-18 standard review
Folic acid + B12 and cancer in Norway
Cancer incidence and mortality after treatment with folic acid and vitamin B12.
Overview
Ebbing M et al.. JAMA 2009 · PMID 19920236 · DOI 10.1001/jama.2009.1622
More cancer and deaths with folic acid plus B12 in heart patients.
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?
Cancer with B vitamins.
- How was the study done?
Pooled RCTs.
- How many people, animals or samples were studied?
6,837.
- What was actually found?
More cancer.
- How large was the observed effect?
HR 1.21.
- What do the results mean in everyday life?
Uncertain signal.
- What are the study's limitations?
Secondary.
- What does it say about Elawady's specific claim?
Partly supports.
- Do the results apply to Germany and Europe?
Norway.
- What can explicitly not be concluded from this study?
General harm.
Scientific in-depth review
1. Full reference
- Authors
- Ebbing M, Bønaa KH, Nygård O, Arnesen E, Ueland PM, Nordrehaug JE, Rasmussen K, Njølstad I, Refsum H, Nilsen DW, Tverdal A, Meyer K, Vollset SE
- Journal
- JAMA
- Year
- 2009
- Identifier
- PMID 19920236 DOI 10.1001/jama.2009.1622
- Verification
- verified – PubMed E-utilities efetch, 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Effect of B vitamins on cancer and mortality
3. Study design and population
- Study design
- Randomised controlled trial – Combined analysis and extended follow-up of two RCTs (NORVIT, WENBIT)
- Population
Ischaemic heart disease patients
- Country
Norway (no fortification)
- Period
1998–2007
- Sample size
6,837
- Inclusion and exclusion criteria
see abstract
4. Methods and endpoints
- Exposure / intervention
Folic acid 0.8 mg + B12 0.4 mg ± B6
- Comparator
No folic acid/B12
- Endpoints
Cancer incidence, cancer mortality, all-cause mortality
- Statistical methods
Cox
5. Actual results
- Results
Cancer 10.0% vs 8.4%, HR 1.21 (1.03–1.41); cancer death HR 1.38 (1.07–1.79); all-cause death HR 1.18 (1.04–1.33); mainly lung cancer.
- Absolute risks
not reported in abstract
- Authors' conclusion
Folic acid + B12 associated with increased cancer outcomes and mortality in Norway.
6. Strengths
- Randomised
7. Weaknesses
- Post-trial observational follow-up
- Not prespecified for cancer
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Secondary outcomes with extended follow-up.
9. Assessment of the statistical interpretation
See results.
10. Relevance to the specific claim
11. Independent contrary findings
Vollset 2013 (I-SUP-07).
12. Transferability to Germany and Europe
High: biology and trial populations comparable to European adults.
13. Overall methodological judgement
Signal not confirmed.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | not replicated |
| Consistency with the overall evidence | inconsistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | partly correct but over-interpreted |
14. Open questions
15. Linked fact checks
Use by the Tayebat archive
Note: according to the archive, the studies were compiled by the archive operators. Whether Dr. Elawady himself cited this study is not established.
- What the archive says about the study
Listed in the archive bibliography of the oral-supplements rule without its own interpretation; used implicitly to support the rule summary that supplements 'failed or caused harm' in large trials.
- A. What was actually studied?
Effect of B vitamins on cancer and mortality
- B. What did the authors find?
Cancer 10.0% vs 8.4%, HR 1.21 (1.03–1.41); cancer death HR 1.38 (1.07–1.79); all-cause death HR 1.18 (1.04–1.33); mainly lung cancer.
- C. What conclusions do the authors themselves draw?
Folic acid + B12 associated with increased cancer outcomes and mortality in Norway.
- D. What does the archive derive from it?
Bibliography support for folic acid/B12 harm.
- E. Is this derivation scientifically justified?
Weak; not confirmed in pooled RCT analysis.
- Adequacy of the interpretation (by the archive)
- partly correct but over-interpreted