STUDY: An Egg A Day Keeps Cognitive Decline Away?
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LA JOLLA, Calif. — Eggs have had a complicated history when it comes to health and nutrition. First, they’re good, then they’re bad, then food scientists say they’re good again. Well, researchers are once again placing all their eggs in the “good” basket, finding that these controversial sources of cholesterol may be even better your our brains than we thought.
A team from the University of California-San Diego has discovered that older women who eat eggs each week may experience less memory loss and less decline in their executive brain functions over time. This is the latest research to suggest that eggs, a food often criticized for their high cholesterol content, could actually benefit cognitive health among certain groups.
The study, published in the journal Nutrients, examined a group of 890 adults over the age of 55 from the Rancho Bernardo study in California. The participants kept track of their egg consumption from 1988 to 1991. They also underwent a series of cognitive tests during that time and once again between 1992 and 1996, measuring their global cognition, executive function, and semantic memory.
When the researchers analyzed the data by sex, they found that among women, those who ate more eggs each week experienced less decline in category fluency — a test of verbal abilities and executive function — over the four-year period. This association remained even after accounting for factors like age, education, lifestyle behaviors, cholesterol levels, and each participant’s calorie and protein intake.
Overall, researchers found that the magic number for older women appears to be five eggs per week. In other words, an egg a day may keep cognitive decline away.
“Women in the highest category of egg intake would have a half-point less decline in category fluency score over 4 years compared to women who never consumed eggs. Although small, this association was still significant after further adjustment for behaviors, cholesterol, and calorie and protein intake, as well as after additional adjustment for diabetes and hypertension,” researchers Donna Kritz-Silverstein and Ricki Bettencourt write in their report.
In contrast, the researchers did not find any significant links between eating eggs and brain changes among men. Kritz-Silverstein notes that this difference among the sexes is intriguing and warrants further investigation.
The exact reason that causes eggs to benefit cognitive health is not fully clear, but the researchers point to some promising clues. Eggs are rich in nutrients like choline, lutein, and zeaxanthin, which have been linked to better brain health in prior research. The high-quality protein in eggs may also help preserve neuronal structure and function.
Additionally, while eggs do contain dietary cholesterol, unlike meat, they have relatively low levels of harmful saturated fat. This may allow them to provide cognitive benefits without the potential downsides associated with high-cholesterol foods. The team also notes that eggs are relatively affordable and accessible, making them a cheap way to get important nutrients for brain health.
“The lack of cognitive decline with egg consumption is reassuring and suggests that despite having high levels of dietary cholesterol, eggs do not have a detrimental effect and may even have a role in the maintenance of cognitive function over time,” the study authors conclude.
Of course, this was an observational study, so more research is necessary to confirm a causal relationship. However, the results add to a growing body of evidence challenging the notion that eggs should be strictly limited in the diet, especially for older adults focused on preserving their mental sharpness.
Paper Summary
Methodology
The researchers analyzed data from 890 adults aged 55 and older who were part of the Rancho Bernardo Study, an ongoing long-term health study in California. Participants reported their weekly egg consumption in 1988-1991, and then completed cognitive tests assessing global cognition, executive function, and semantic memory in both 1988-1991 and 1992-1996.
The team looked at how participants’ egg intake related to changes in their test scores over the 4-year period, running separate analyses for men and women to account for potential sex differences. They adjusted the results to control for factors like age, education, lifestyle behaviors, cholesterol levels, and calorie/protein intake.
Key Results
The key finding was that among women, greater egg consumption was associated with less decline in category fluency – a test of verbal abilities and executive function – over the 4 years. Specifically, women who reported eating 5 or more eggs per week had about a half-point less decline in their category fluency scores compared to women who never ate eggs.
This association held up even after accounting for various demographic, health, and dietary factors. In contrast, the researchers did not find any significant links between egg intake and cognitive changes in men.
Study Limitations
While the results are intriguing, this was an observational study, so it cannot prove that eating more eggs directly causes cognitive benefits. The participants were also predominantly white and well-educated, which limits the generalizability of the findings.
Additionally, the 4-year follow-up period was relatively short. Longer-term studies are needed to see if the apparent cognitive advantages of egg consumption persist over time.
Discussion & Takeaways
The researchers propose several plausible mechanisms by which eggs could help preserve cognitive abilities, particularly in women. Eggs are rich in nutrients like choline, lutein, and zeaxanthin, which have been linked to better brain health in prior research. The high-quality protein in eggs may also help maintain neuronal structure and function.
Importantly, while eggs do contain dietary cholesterol, they have relatively low levels of harmful saturated fat compared to other high-cholesterol foods like red meat. This may allow eggs to provide cognitive benefits without the potential downsides.
The sex differences in the findings are intriguing and warrant further investigation. The researchers note that women in the study had lower rates of diabetes but also less education and exercise than the men – factors that could influence cognitive aging in complex ways.
Funding & Disclosures
This research was funded by an unrestricted grant from the American Egg Board’s Egg Nutrition Center. The original data collection was supported by grants from the National Institutes of Health. The authors declare no conflicts of interest.
