Randomised controlled trialindependent cross-checkabstract only checked★ key study I-SUP-01 in-depth review
Folic acid prevents spina bifida (MRC trial)
Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group.
Overview
MRC Vitamin Study Research Group. Lancet 1991 · PMID 1677062
Folic acid cut neural tube defects by 72%.
Does the study support the specific claim? No · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
NTD prevention.
- How was the study done?
RCT.
- How many people, animals or samples were studied?
1,817 women.
- What was actually found?
Fewer NTDs.
- How large was the observed effect?
RR 0.28.
- What do the results mean in everyday life?
Folic acid before pregnancy is essential.
- What are the study's limitations?
High-risk women.
- What does it say about Elawady's specific claim?
Contradicts blanket ban.
- Do the results apply to Germany and Europe?
Applicable.
Scientific in-depth review
1. Full reference
- Authors
- MRC Vitamin Study Research Group
- Journal
- Lancet
- Year
- 1991
- Identifier
- PMID 1677062
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Does periconceptional folic acid or other vitamins prevent neural tube defect recurrence?
3. Study design and population
- Study design
- Randomised controlled trial – Randomised double-blind factorial prevention trial (MRC Vitamin Study)
- Population
Women with a previous NTD-affected pregnancy
- Country
33 centres, 7 countries
- Sample size
1,817 women; 1,195 completed pregnancies
- Inclusion and exclusion criteria
High-risk women
4. Methods and endpoints
- Exposure / intervention
Folic acid (dose not stated in abstract) and/or a mixture of seven other vitamins
- Comparator
No folic acid
- Endpoints
NTD
- Statistical methods
RR
5. Actual results
- Results
27 NTDs: 6 in folic acid groups vs 21 in others; RR 0.28 (0.12–0.71), 72% protective effect; other vitamins RR 0.80 (n.s.); no demonstrable harm.
- Absolute risks
6 vs 21 NTDs among 1,195 pregnancies
- Authors' conclusion
Folic acid before pregnancy firmly recommended for women with an affected pregnancy; public health measures for all women.
6. Strengths
- Landmark RCT
7. Weaknesses
- High-risk population (recurrence, not first occurrence)
- Folic acid dose not given in abstract
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Simplified.
9. Assessment of the statistical interpretation
Large effect.
10. Relevance to the specific claim
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Foundational evidence for folic acid.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- No one needs vitamins or supplements: 'there is no such thing as dietary supplements', the body makes its own vitamins, and vitamins are on the forbidden list. – Studies contradicting or limiting the claim