Cohort studyindependent cross-checkabstract checked★ key study I-EGG-118 in-depth review
US cohorts: frequent egg eaters had more diabetes
Egg consumption, overall diet quality, and risk of type 2 diabetes and coronary heart disease: A pooling project of US prospective cohorts.
Overview
Djoussé L et al.. Clin Nutr 2021 · PMID 33932789 · DOI 10.1016/j.clnu.2021.03.003
Eating 7+ eggs a week was linked to 27% higher type 2 diabetes risk; under 2 eggs a week was not.
Does the study support the specific claim? Partly · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test eggs and diabetes/CHD in US cohorts.
- How was the study done?
Pooled individual-level cohort analysis.
- How many people, animals or samples were studied?
103,811 adults.
- What was actually found?
Higher T2D risk at >=2 eggs/week; no CHD association overall.
- How large was the observed effect?
+27% (16%-37%) for 7+/week.
- What do the results mean in everyday life?
In the USA, frequent egg eating goes with more diabetes; it is unclear whether eggs are the cause.
- What are the study's limitations?
US only; observational.
- What does it say about Elawady's specific claim?
Supports the US part of the claim.
- Do the results apply to Germany and Europe?
Low.
- What can explicitly not be concluded from this study?
It cannot prove causation or apply to other regions.
Scientific in-depth review
1. Full reference
- Authors
- Djoussé L et al.
- Journal
- Clin Nutr
- Year
- 2021
- Identifier
- PMID 33932789 DOI 10.1016/j.clnu.2021.03.003
- 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
NIH grants; first author received an investigator-initiated grant from the American Egg Board for these analyses (sponsor reportedly had no influence).
2. Research question
Is frequent egg consumption associated with T2D and CHD after adjustment for overall dietary pattern?
3. Study design and population
- Study design
- Cohort study – Pooled de novo harmonised individual-level analyses of 9 US prospective cohorts
- Population
103,811 adults in 9 US cohorts (median age 25-72 years)
- Country
USA
- Period
not stated in abstract
- Sample size
103,811
- Inclusion and exclusion criteria
not detailed in abstract
4. Methods and endpoints
- Exposure / intervention
Egg consumption (categories up to 7+/week)
- Comparator
No egg consumption
- Endpoints
Incident type 2 diabetes; coronary heart disease
- Statistical methods
Cohort-specific Cox models adjusted for age, ethnicity, BMI, exercise, smoking, alcohol, dietary pattern; inverse-variance pooling
5. Actual results
- Results
Up to 1 egg/week not associated with T2D; >=2 eggs/week associated with elevated risk; 7+ eggs/week vs none: +27% T2D risk (95% CI 16%-37%); little heterogeneity across cohorts. No overall association with CHD; sensitivity analysis: +30% (3%-56%) CHD risk in older adults eating 5-6 eggs/week.
- Absolute risks
not reported
- Authors' conclusion
Elevated T2D risk with >=2 eggs/week but not <2/week; no overall association with CHD.
6. Strengths
- Individual-level harmonised analysis
- Adjusted for overall dietary pattern
7. Weaknesses
- US only
- Funding from American Egg Board (result nevertheless unfavourable to eggs)
- Observational
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
Residual confounding possible; simplified judgement.
9. Assessment of the statistical interpretation
7+ eggs/week HR about 1.27 (1.16-1.37); CI slightly asymmetric on log scale, compatible with rounding of percentages (stats/C-EGG-07_diabetes_regions.py).
10. Relevance to the specific claim
Supports a positive egg-T2D association in US populations, even after adjusting for diet quality.
11. Independent contrary findings
Non-US cohorts show no association (I-EGG-08, A-EGG-14); RCTs in prediabetes/T2D show no harm (I-EGG-119).
12. Transferability to Germany and Europe
Limited: European/Asian data differ.
13. Overall methodological judgement
Credible US signal; region-specific.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | low |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Mechanism and reason for US specificity.
15. Linked fact checks
- Higher egg intake is linked to type 2 diabetes. – Studies supporting the claim