Eggs have had a complicated life in health research. One decade they're nutritional heroes, packed with protein and essential nutrients. The next, they're dietary villains blamed for contributing to cholesterol woes and heart disease fears.

Now, research is adding yet another twist to the egg story — one may be especially important for aging Americans worried about memory loss and dementia.

A new study suggests that regularly eating eggs may significantly lower the risk of developing Alzheimer's disease. The research found that older adults who consumed eggs at least five times a week had up to a 27 percent lower risk of Alzheimer's disease compared to people who rarely or never ate them. Lower consumption was beneficial too — participants who ate eggs just one to three times per month still showed a 17 percent reduction in dementia risk.

Eggs are rich in lutein and zeaxanthin, antioxidants that accumulate in brain tissue and may help reduce oxidative stress, one of the destructive processes associated with aging and neurodegeneration.

That's an intriguing finding in a country where Alzheimer's disease currently affects more than 7 million Americans; a number expected to rise dramatically as the population ages.

The study was conducted at Loma Linda University School of Public Health using data from the large Adventist Health Study-2 cohort, which has followed tens of thousands of adults over many years to examine links between lifestyle habits and disease. For this analysis, investigators focused on nearly 40,000 adults age 65 and older.

People in the study completed detailed dietary questionnaires that tracked not only obvious egg consumptions, such as scrambled or boiled eggs, but also “hidden” eggs found in baked goods and processed foods. Researchers then linked those dietary records with Medicare diagnostic data and followed participants for an average of 15.3 years. Over that period, 2,858 participants developed Alzheimer's disease.

The goal was to better understand whether a simple dietary habit might influence brain health over time, lead author Jisoo Oh, an associate professor of epidemiology at Loma Linda University School of Public Health, explained in a press release. “Eggs are widely consumed and contain several nutrients relevant to brain function, yet the evidence linking egg intake to clinically diagnosed Alzheimer's disease has been limited.”

People who ate eggs at least five times a week had up to a 27 percent lower risk of Alzheimer's disease compared to people who rarely ate them. Egg consumption included eggs in baked goods and other foods.

The protective effect of eggs may come from several nutrients concentrated in eggs, particularly choline, a compound researchers believe the brain uses to produce acetylcholine, a neurotransmitter essential for memory and communication between brain cells.

Eggs are also rich in lutein and zeaxanthin, antioxidants that accumulate in brain tissue and may help reduce oxidative stress, one of the destructive processes associated with aging and neurodegeneration. In addition, eggs contain omega-3 fatty acids, vitamin B12, phospholipids and high-quality protein — all thought to support cognitive health.

The researchers aren't claiming that eggs are a miracle food or a stand-alone dementia prevention strategy. They stress that eggs appear most beneficial as part of an overall healthy eating pattern rich in fruits, vegetables, whole grains and other nutrient-dense foods.

That context matters because the study population was unusually health-conscious. People in the study were members of a Seventh-day Adventist community, a group known for relatively low rates of smoking and alcohol use and generally healthier lifestyles than the average American and the results may not fully apply to everyone. The study was also observational, meaning it can only show an association, not prove that eggs directly prevent Alzheimer's disease.

In the end, the humble egg may turn out to be far more than a breakfast staple. As scientists continue searching for ways to slow the rise of Alzheimer's disease, simple lifestyle habits, including diet, are emerging as powerful tools for protecting the aging brain.

The study is published in The Journal of Nutrition.