Randomised controlled trialindependent cross-checkabstract checked I-EGG-134 standard review
Eggs briefly raise TMAO after a meal
Effect of egg ingestion on trimethylamine-N-oxide production in humans: a randomized, controlled, dose-response study.
Overview
Miller CA et al.. Am J Clin Nutr 2014 · PMID 24944063 · DOI 10.3945/ajcn.114.087692
Eating 2 or more egg yolks raised TMAO in blood and urine over the next day, without changes in inflammation markers.
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?
Test whether eggs raise TMAO.
- How was the study done?
Randomized dose-response feeding study.
- How many people, animals or samples were studied?
6 volunteers.
- What was actually found?
Acute TMAO rise; no inflammation change.
- How large was the observed effect?
About 14% of egg choline converted to TMAO.
- What do the results mean in everyday life?
Eggs can briefly raise TMAO, but this has not been shown to harm the heart.
- What are the study's limitations?
Tiny, short study.
- What does it say about Elawady's specific claim?
Supports the mechanism step only.
- Do the results apply to Germany and Europe?
Universal.
- What can explicitly not be concluded from this study?
It cannot show any effect on heart events.
Scientific in-depth review
1. Full reference
- Authors
- Miller CA et al.
- Journal
- Am J Clin Nutr
- Year
- 2014
- Identifier
- PMID 24944063 DOI 10.3945/ajcn.114.087692
- 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
Egg Nutrition Center and NIH grants (full-text footnote); funders reportedly had no role.
2. Research question
Does eating eggs raise TMAO, and is this linked to inflammation or LDL oxidation?
3. Study design and population
- Study design
- Randomised controlled trial – Randomized, double-blind, crossover dose-response feeding study
- Population
6 healthy volunteers
- Country
USA
- Period
not stated in abstract
- Sample size
6
- Inclusion and exclusion criteria
not detailed in abstract
4. Methods and endpoints
- Exposure / intervention
Breakfast doses of 1, 2, 4 or 6 egg yolks
- Comparator
0 egg yolks (low-choline controlled diet)
- Endpoints
Plasma and 24-h urine TMAO; hsCRP; oxidised LDL
- Statistical methods
Repeated-measures comparisons
5. Actual results
- Results
Egg consumption increased plasma and urine TMAO (P < 0.01); about 14% of egg choline was converted to TMAO; large between-person variation. No differences in hsCRP or oxidised LDL after egg doses.
- Absolute risks
not reported
- Authors' conclusion
Consumption of >=2 eggs results in increased TMAO formation; more research is needed before recommending reduced choline intake.
6. Strengths
- Randomized, controlled background diet
- Dose-response design
7. Weaknesses
- Only 6 participants
- Acute (24-h) effects only
- Industry co-funding
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
Very small sample; simplified judgement.
9. Assessment of the statistical interpretation
Shows acute post-meal TMAO rises; fasting levels after weeks of egg eating did not rise in later RCTs (I-EGG-10, I-EGG-113).
10. Relevance to the specific claim
Supports the first mechanistic step (eggs can transiently raise TMAO); found no change in inflammation or LDL oxidation markers.
11. Independent contrary findings
Longer RCTs found no rise in fasting TMAO.
12. Transferability to Germany and Europe
Universal biology.
13. Overall methodological judgement
Real but small and transient effect; does not demonstrate cardiovascular harm.
| 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 | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Clinical relevance of post-meal TMAO peaks.