Systematic reviewindependent cross-checkfull text checked I-INTA-13 in-depth review
Do eggs cause dementia?
Egg intake and cognitive function in healthy adults: A systematic review of the literature.
Overview
Sultan N et al.. The journal of nutrition, health & aging 2025 · PMID 41061594 · DOI 10.1016/j.jnha.2025.100696
Eleven mostly observational studies did not show that eggs cause dementia; several found no link, some found better results with moderate intake, and one cross-sectional study found more mild cognitive impairment at the highest intake.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Eggs and brain health
- How was the study done?
Systematic review
- How many people, animals or samples were studied?
11 studies, >38,000 people
- What was actually found?
Mostly neutral or favourable for moderate intake; one adverse signal at high intake
- How large was the observed effect?
Not pooled
- What do the results mean in everyday life?
Eggs are not a known cause of Alzheimer's disease
- What are the study's limitations?
Inconsistent, mostly observational studies; English-only search; first author's scholarship partly funded by the egg industry
- What does it say about Elawady's specific claim?
Contradicts 'eggs cause Alzheimer's'
- Do the results apply to Germany and Europe?
Moderate
- What can explicitly not be concluded from this study?
Causal effects, and nothing specific about Alzheimer's disease (not studied separately)
Scientific in-depth review
1. Full reference
- Authors
- Sultan N et al.
- Journal
- The journal of nutrition, health & aging
- Year
- 2025
- Identifier
- PMID 41061594 DOI 10.1016/j.jnha.2025.100696
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- full text
- Conflicts of interest and funding
First author supported by a PhD scholarship partly funded by Australian Eggs Ltd (GROW005); funder reportedly not involved in design, analysis, interpretation or writing; another author holds an NHMRC fellowship. No separate competing-interest statement found in the full text.
2. Research question
Association between whole egg consumption and cognitive function in healthy adults
3. Study design and population
- Study design
- Systematic review – Systematic review with structured narrative synthesis (no meta-analysis); PROSPERO 408532
- Population
Adults >=18 years without diagnosed chronic metabolic/cardiovascular disease, or cohorts statistically adjusted for chronic disease; mostly older adults; 11 studies (1 pre-post, 6 prospective cohorts, 3 cross-sectional, 1 case-control) from China (6), USA (3), Thailand (1), Finland (1)
- Country
China, USA, Thailand, Finland
- Period
Databases searched from inception to April 2023, updated February 2025; included studies published 2016-2024 (data collected 1984-2020)
- Sample size
11 studies, 38,722 participants
- Inclusion and exclusion criteria
Whole chicken egg intake (any amount) and any cognitive outcome in healthy adults; English-language human studies; excluded animal/child studies, isolated egg components, reviews/case reports; 5 otherwise eligible studies excluded for not adjusting for chronic disease. 1,356 records, 68 full texts.
4. Methods and endpoints
- Exposure / intervention
Whole egg intake (FFQ, 24-h recalls, food records, interview; one 8-week feeding of 2 eggs/day)
- Comparator
Lower or no egg intake; pre-intervention values in the pre-post study
- Endpoints
Global cognition, memory, verbal learning, language, processing speed, executive function, reaction time, cognitive impairment (MoCA/MMSE), incident dementia; no study reported Alzheimer's disease specifically
- Statistical methods
Narrative synthesis by cognitive domain; risk of bias with ROBINS-E (cohorts), ROBINS-I (pre-post), JBI checklists (cross-sectional, case-control), assessed in duplicate.
5. Actual results
- Results
Mostly null or favourable for moderate intake: KIHD (Finland, men) highest egg quartile vs lowest incident dementia HR 0.74 (0.53-1.02), not significant after cholesterol adjustment (0.78, 0.51-1.19); Zhejiang cohort cognitive impairment RR 0.78 (0.67-0.91) for eggs 1-2 days/week vs none, but 0.94 (0.83-1.07) for highest intake; Chinese case-control: daily vs monthly egg intake dementia OR 0.21 (0.08-0.53); CHNS higher global cognition in Q4. Adverse signals: Huang 2021 cross-sectional MCI OR 1.23 (1.03-1.48) for highest vs lowest quartile (about 60 g/day); An 2019 lower executive function with higher intake (beta -0.000022). Null: NHANES, CLHLS, HRS. Pre-post (n=15): reaction time 17% faster after 8 weeks of 2 eggs/day. Risk of bias: 4 of 6 cohorts low, 2 some concerns (unvalidated intake tools).
- Absolute risks
not reported in full text
- Authors' conclusion
Moderate whole egg consumption may be associated with improved cognitive outcomes in healthy adults, including reduced dementia risk and better memory, but findings are inconsistent and limited by design, dietary assessment and testing differences; well-controlled intervention studies are needed.
6. Strengths
- Pre-registered on PROSPERO; five databases; librarian-supported search
- Duplicate screening and duplicate risk-of-bias assessment with design-appropriate tools
- Funding of included studies extracted
7. Weaknesses
- English-only; small number of heterogeneous studies; no meta-analysis
- Mostly observational (cross-sectional and case-control included); residual confounding and reverse causation (cognitive decline may change diet)
- Exposure measured by FFQs or brief screeners, some unvalidated; inconsistent intake categories
- Only one tiny pre-post feeding study (n=15, young men)
- No Alzheimer's-specific outcome; no Middle Eastern populations
- First author's scholarship partly funded by the egg industry (Australian Eggs Ltd)
- Conclusion emphasises benefits although several studies were null and two showed adverse signals
8. Risk of bias
- Orienting tool
- AMSTAR 2 (adapted; no meta-analysis)
- Type of assessment
- structured assessment based on the full text by a single reviewer (no formal double review)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Overall unchanged. Industry co-funding of the first author's scholarship is disclosed. Simplified single-reviewer judgement from the full text; a formal AMSTAR 2 assessment needs two independent reviewers.
| Domain | Judgement | Rationale |
|---|---|---|
| Item 1 PICO | low | Population, exposure and outcomes defined. |
| Item 2 (critical) protocol | low | PROSPERO registration March 2023 (408532). |
| Item 4 (critical) comprehensive search | some concerns | Five databases with librarian input, but English-only and no grey literature. |
| Items 5-6 duplicate selection and extraction | low | Independent duplicate screening; extraction verified by second author. |
| Item 7 (critical) excluded studies | some concerns | Flow diagram; 5 near-eligible studies cited with reason; full list of excluded full texts not provided in main text. |
| Item 9 (critical) RoB of individual studies | low | ROBINS-E, ROBINS-I and JBI tools in duplicate. |
| Item 10 funding of included studies | low | Funding source extracted. |
| Items 11, 12, 15 meta-analysis items | not applicable | No meta-analysis performed. |
| Item 13 (critical) RoB in interpretation | some concerns | Limitations stated, but conclusion leans toward benefit despite mixed/null findings. |
| Item 14 heterogeneity | low | Heterogeneity discussed as reason for narrative synthesis. |
| Item 16 review COI | some concerns | First author's scholarship partly funded by Australian Eggs Ltd; disclosed with statement of funder non-involvement. |
Full-text review (25 October 2026): Added PROSPERO registration, search details (English-only), study list by design/country, key effect sizes (KIHD HR 0.74, 0.53-1.02; Huang MCI OR 1.23, 1.03-1.48; Li RR 0.78), RoB results, absence of Alzheimer-specific outcomes, and funding (first author's PhD scholarship partly funded by Australian Eggs Ltd). Bias overall unchanged with itemised AMSTAR 2.
9. Assessment of the statistical interpretation
No pooled estimate. Individual estimates are mostly null or modestly favourable for moderate intake; two adverse signals (one cross-sectional, one cohort with a negligible coefficient). None of the studies examined Alzheimer's disease as a specific outcome.
10. Relevance to the specific claim
Tests 'eggs cause Alzheimer's'.
11. Independent contrary findings
One study found higher risk at more than 1 egg/day.
12. Transferability to Germany and Europe
Moderate.
13. Overall methodological judgement
Low-certainty observational evidence; no consistent signal that eggs harm cognition or cause dementia; possible modest benefit at moderate intake is unproven. Industry-linked funding of the first author noted.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Intervention studies.
15. Linked fact checks
- Food should not be judged by its nutrient components (such as choline and lecithin in eggs); eggs cause sinus allergy, fermentation in the stomach, bad breath, protein leakage into the urine, Alzheimer's disease, foul-smelling discharge and recurrent vaginal infections (the passage continues with recurrent urinary infections). – Studies contradicting or limiting the claim