Egg intake and cognitive function in healthy adults: A systematic review of the literature

Abstract

Background: Cognitive decline is a growing public health concern, particularly in aging populations. Eggs are a widely consumed, nutrient-dense food containing choline, phospholipids, tryptophan, and omega-3 fatty acids, which individually support cognitive processes such as memory, attention, and neurogenesis. While these individual nutrients have demonstrated benefits in supplementation studies, the cognitive effects of whole egg consumption are not well established. This systematic review aimed to evaluate the association between whole egg consumption and cognitive function in healthy adults.

Methods: A systematic search of five electronic databases (Medline, Embase, CINAHL Plus, SCOPUS, and PsychInfo) was conducted from database inception through February 2025. Studies were included if they investigated whole egg intake in relation to cognitive outcomes in healthy adults. Risk of bias was assessed using tools appropriate to study design. Due to heterogeneity in study methods, outcomes were synthesised narratively. Cognitive outcomes were categorised into domains including global cognitive function, memory, executive function, language, processing speed, and dementia risk.

Results: Eleven studies met the inclusion criteria: one pre-post intervention study, six prospective cohort studies, three cross-sectional studies, and one case-control study. Study populations were predominantly older adults and included >38,000 participants. Two studies reported a reduced risk of dementia or cognitive impairment associated with moderate egg consumption (approximately 0.5-1 egg per day), while one study found increased risk at high intake levels (Over 1 egg per day). Several studies showed improvements in memory, verbal fluency, or processing speed with moderate-but not high-egg intake. The pre-post study reported improved reaction time following eight weeks of daily egg consumption (2 eggs per day). Heterogeneity in exposure measurement and cognitive testing methods limited direct comparisons across studies.

Discussion: Moderate whole egg consumption may be associated with improvements in cognitive outcomes in healthy adults, including reduced dementia risk and better memory performance. However, findings are inconsistent and limited by differences in study design, dietary assessment, and cognitive testing. Further well-controlled intervention studies are needed to determine optimal intake levels, explore mechanisms, and assess whether eggs can be integrated meaningfully into dietary strategies to support cognitive aging. (PROSPERO registration: 408532).

Keywords: Aging; Cognition; Dementia; Eggs; Nutrition; Systematic review.

Fig. 1

PRISMA flow diagram of study selection. Review 2 (eggs + brain) studies included in narrative synthesis (n = 11).

Fig. 2

Risk of bias assessments (A) ROBINS-E [[44], [45], [46], [47], [48], [49]], (B) JBI for cross sectional studies [[41], [42], [43]], (C) JBI for case control studies [50], (D) ROBINS-I [40]. For ROBINS-E: D1, Bias due to confounding; D2, Bias arising from measurement of exposure; D3, Bias in selection of participants into the study (or into the analysis); D4, Bias due to post-exposure interventions; D5, Bias due to missing data; D6, Bias arising from measurement of the outcome; D7, Bias in selection of reported result. For JBI for cross-sectional studies:: 1,Were the criteria for inclusion in the sample clearly defined; 2, Were the study subjects and the setting described in detail; 3, Was the exposure measured in a valid and reliable way; 4, Were objective, standard criteria used for measurement of the condition; 5, Were confounding factors identified; 6, Were strategies to deal with confounding factors stated; 7. Were the outcomes measured in a valid and reliable way; 8, Was appropriate statistical analysis used. For JBI for case control studies: 1. Were the groups comparable other than the presence of disease in cases or the absence of disease in controls; 2. Were cases and controls matched appropriately; 3. Were the same criteria used for identification of cases and controls; 4. Was exposure measured in a standard, valid and reliable way; 5. Was exposure measured in the same way for cases and controls; 6. Were confounding factors identified; 7. Were strategies to deal with confounding factors stated; 8. Were outcomes assessed in a standard, valid and reliable way for cases and controls; 9. Was the exposure period of interest long enough to be meaningful; 10. Was appropriate statistical analysis used. ROBINS-I: D1, Bias due to confounding; D2: Bias due to classification of intervention; D3: Bias in selection of participants into the study (or into the analysis); D4: Bias due to missing data; D5: Bias due to deviations from intended intervention; D6: Bias due to outcome measurement; D7: Bias due to selection of reported results. Green “+/Y” = low risk of bias, yellow “−/N” = moderate risk of bias (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).