Effect of egg consumption on circulating choline, betaine, and trimethylamine n-oxide in adults: a systematic review and meta-analysis of randomized controlled trials
Aryaeian N, Heydarian A, Tahvilian N, Hosseini H, Ahmadi AR, Davarpanah SH
Nutrition journal · 2 citations
How it was studied
- Design
- Meta-analysis (indexed by PubMed)
- Studied in
- People
- Main outcome
- Health markers and function
- Intake measured by
- Not stated
Who paid for it
- Funding
- Independent funding
- University or hospital
- Iran University of Medical Sciences
Based on 1 listed funder(s).
Publication
- Published
- 2025-10-27 · Nutr J · vol. 24 · issue 1 · p. 165
- Publisher
- BioMed Central
- Cited
- 4 citations · more than 76% of similar papers · 1.1× the field average
- References
- 64 works
- Access
- Open access (journal) · CC-BY-NC-ND
- Research areas
- Folate and B Vitamins Research · Metabolism and Genetic Disorders · Alcoholism and Thiamine Deficiency
- Keywords
- Randomized controlled trial, Choline, Betaine, Trimethylamine, Consumption (sociology)
- MeSH
- humans, choline, betaine, methylamines, diet, eggs, adult, middle aged, female, male, randomized controlled trials as topic
6 authors
From IR
- Naheed AryaeianIran University of Medical Sciences
- Azadeh HeydarianIran University of Medical Sciences
- Negin TahvilianShahid Sadoughi University of Medical Sciences and Health Services
- Hossein Mirshojaeian HosseiniUrmia University; Urmia University of Medical Sciences
- Amirhossein Ramezani AhmadiIsfahan University of Medical Sciences
- Seyedeh Hajar Davarpanah · correspondingIran University of Medical Sciences; Tehran University of Medical Sciences
Abstract
Background and objective
Eggs are rich in choline and other methyl donors that may influence metabolic health, yet their effects on circulating metabolites such as choline, betaine, and trimethylamine N-oxide (TMAO) remain unclear. Understanding these effects is critical due to potential links with cardiometabolic risk. This study aimed to systematically evaluate and quantitatively synthesize the effects of egg consumption on plasma levels of choline, betaine, and TMAO in randomized controlled trials (RCTs), and to explore potential effect modifiers.
Methods
A systematic search of electronic databases was conducted to identify RCTs examining the effects of egg consumption on circulating choline, betaine, and TMAO. Data were pooled using random-effects meta-analyses. Subgroup analyses were performed based on age, body mass index, health status, study design, duration, and egg dosage. Meta-regression was conducted to assess the influence of age, dose, and duration. Publication bias was evaluated using Egger's and Begg's tests, funnel plots, and trim-and-fill analysis. The certainty of evidence was assessed using the NutriGRADE tool, which is specifically recommended for nutrition meta-analyses.
Results
Six RCTs (n = 5 for betaine and TMAO; n = 6 for choline) were included. Multi-arm trials were combined into single pairwise comparisons per outcome, as per Cochrane Handbook Sect. 23.3.4, to avoid unit-of-analysis errors. No significant overall effects were observed for choline (WMD = 0.10; 95% CI: - 0.92 to 1.12; p = 0.847), betaine (WMD = 0.21; 95% CI: - 8.50 to 8.92; p = 0.962), or TMAO (WMD = - 0.08; 95% CI: - 0.47 to 0.32; p = 0.692). High heterogeneity was noted for choline and betaine (I² > 85%), but low for TMAO (I² = 23%). Subgroup analyses showed significant choline increases among older adults (> 45 years) and individuals with metabolic syndrome or obesity. Meta-regression revealed a negative association between egg dose and both choline and betaine levels (p < 0.001). Publication bias was suggested for betaine but not for choline or TMAO. The NutriGRADE assessment indicated moderate certainty of evidence for choline (score 7.75), betaine (7.05), and TMAO (7.25), with downgrades mainly due to imprecision and heterogeneity.
Conclusions
No clear effect of egg consumption on circulating choline, betaine, or TMAO levels could be demonstrated. Age and metabolic status may influence choline responses, and higher egg doses may attenuate choline and betaine levels. Based on NutriGRADE, the overall certainty of evidence was rated as moderate for all three outcomes. Further long-term, high-quality RCTs are needed to clarify these associations.
Abstract via Europe PMC. Copyright remains with the authors or publisher (CC BY-NC-ND).
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