A large, long-term study links regular egg consumption to a significantly lower risk of Alzheimer's disease in older adults, though researchers caution the findings show correlation, not causation.
A study published in The Journal of Nutrition has identified an association between egg consumption and a lower risk of developing Alzheimer's disease in adults aged 65 and older. The research, conducted by scientists at Loma Linda University Health, analyzed data from a large cohort over an extended follow-up period.
Study Methodology
Researchers analyzed data from the Adventist Health Study-2 (AHS-2) cohort, which was linked with Medicare records. The study included approximately 40,000 participants aged 65 and older at the start of the study. Participants' dietary intake, including egg consumption, was assessed using a food frequency questionnaire at baseline. Alzheimer's disease diagnoses were identified using Medicare diagnostic codes from hospital visits and doctor appointments. The participants were followed for an average of 15.3 years. During this period, 2,858 participants developed Alzheimer's disease.
Key Findings
After adjusting for demographic, lifestyle, and other dietary factors, the study found that any level of egg consumption was associated with a lower risk of Alzheimer's disease diagnosis compared to never or rarely eating eggs. The specific risk reductions reported were as follows:
- 17% lower risk for those who ate eggs 1 to 3 times per month.
- 20% lower risk for those who ate eggs 2 to 4 times per week.
- Up to 27% lower risk for those who ate eggs at least 5 times per week.
The study measured both "visible" egg consumption (e.g., scrambled, fried, boiled) and "hidden" consumption (e.g., eggs used in baked goods and packaged foods). A substitution analysis indicated that eggs specifically, rather than other protein-rich foods, were associated with the lower risk.
Nutrient Context
Eggs contain several nutrients that are known to support brain health, including choline, lutein, zeaxanthin, omega-3 fatty acids, vitamin B12, and phospholipids. Researchers have hypothesized that these nutrients may play a role in the observed association.
Study Limitations
The researchers noted several limitations of the study:
- The study is observational, meaning it can show an association but cannot establish causation. Residual confounding from unmeasured factors cannot be ruled out.
- Dietary intake, including egg consumption, was measured only once at the beginning of the study.
- Reliance on Medicare data may miss mild or undiagnosed cases of Alzheimer's disease.
- The study cohort consisted primarily of Seventh-day Adventists, a population that generally follows a healthier diet and lifestyle than the general US population, including lower rates of smoking and alcohol use. This may limit the generalizability of the findings to other populations.
Funding
The study received partial funding from an investigator-initiated grant from the American Egg Board. The original AHS-2 cohort was established with funding from the National Institutes of Health and the National Cancer Institute. The study authors stated that the funding sources had no role in the study's design, execution, analysis, or publication.
Author Statements
Jisoo Oh, DrPH, MPH, lead author and associate professor of epidemiology at Loma Linda University School of Public Health, stated that moderate egg consumption was associated with a lower risk of Alzheimer's disease in this cohort. She emphasized that the findings should be considered within the context of overall dietary patterns.
Joan Sabaté, MD, DrPH, principal investigator and professor at Loma Linda University School of Public Health, stated that compared to never eating eggs, eating at least five eggs per week was associated with a decrease in Alzheimer's disease risk.
External experts not involved in the study, including Dr. Joel Salinas, a behavioral neurologist, noted that while the finding is consistent with prior research, the observational data cannot establish causation. Dietitian Michelle Routhenstein emphasized that the benefits observed likely reflect the addition of eggs to an already healthy and protective diet.