Meta-analysisindependent cross-checkabstract checked I-LEG-124 standard review
Vegetarian diets and iron stores
The effect of vegetarian diets on iron status in adults: A systematic review and meta-analysis.
Overview
Haider LM et al.. Crit Rev Food Sci Nutr 2018 · PMID 27880062 · DOI 10.1080/10408398.2016.1259210
Adult vegetarians had lower iron stores than meat eaters.
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?
Compare iron stores.
- How was the study done?
Meta-analysis.
- How many people, animals or samples were studied?
24 studies.
- What was actually found?
Lower ferritin in vegetarians.
- How large was the observed effect?
-29.71 ug/L.
- What do the results mean in everyday life?
Meat-free diets need attention to iron.
- What are the study's limitations?
Cross-sectional.
- What does it say about Elawady's specific claim?
Partly supports C-LEG-08.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
It says nothing about legumes in mixed diets.
Scientific in-depth review
1. Full reference
- Authors
- Haider LM et al.
- Journal
- Crit Rev Food Sci Nutr
- Year
- 2018
- Identifier
- PMID 27880062 DOI 10.1080/10408398.2016.1259210
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref works API
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Not stated in abstract.
2. Research question
Do adult vegetarians have lower iron stores than non-vegetarians?
3. Study design and population
- Study design
- Meta-analysis – Systematic review and meta-analysis (mainly cross-sectional studies)
- Population
Adult vegetarians vs non-vegetarians
- Country
International
- Period
Not stated
- Sample size
27 cross-sectional and 3 interventional studies (24 in meta-analysis)
- Inclusion and exclusion criteria
Studies reporting serum ferritin.
4. Methods and endpoints
- Exposure / intervention
Vegetarian diet
- Comparator
Non-vegetarian diet
- Endpoints
Serum ferritin
- Statistical methods
Inverse-variance random-effects meta-analysis
5. Actual results
- Results
Vegetarians had lower serum ferritin (-29.71 ug/L, 95% CI -39.69 to -19.73); men -61.88, premenopausal women -17.70 ug/L.
- Absolute risks
Not reported
- Authors' conclusion
Vegetarians are more likely to have lower iron stores; everyone should monitor iron status and improve bioavailability.
6. Strengths
- Quantitative synthesis
7. Weaknesses
- Cross-sectional data
- Whole-diet comparison, not legumes specifically
- Abstract only
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Observational, confounding.
9. Assessment of the statistical interpretation
Lower stores, not necessarily more anaemia.
10. Relevance to the specific claim
Supports the archive's point that plant-based diets supply less bioavailable iron (C-LEG-08), but concerns meat-free diets, not legumes eaten with a mixed diet.
11. Independent contrary findings
A-LEG-06 (balanced diet with animal protein: legumes not a mineral risk).
12. Transferability to Germany and Europe
Applicable.
13. Overall methodological judgement
Relevant to vegetarians; irrelevant to banning legumes in mixed diets.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | indirect |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
None specific.
15. Linked fact checks
- Phytic acid in legumes inhibits iron and zinc absorption; iron bioavailability is 5-12% from vegetarian diets versus 14-18% from mixed diets. – Studies with mixed or unclear results