A healthy diet may do more than just keep your body fit—it could also protect your brain, even if you are at high genetic risk for Alzheimer’s disease.
A new study led by researchers from Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard found that people who followed a Mediterranean-style diet had a lower chance of developing dementia.
The effect was especially strong in people who carried genes that put them at the greatest risk for Alzheimer’s.
The research, published in Nature Medicine, focused on the Mediterranean diet because it is the only eating pattern that has been proven in clinical trials to improve brain health.
This diet is rich in fruits, vegetables, whole grains, fish, beans, nuts, and olive oil, while limiting red meat and processed foods.
Yuxi Liu, Ph.D., the first author of the study, explained that the team wanted to know if the benefits of this diet varied depending on a person’s genetic makeup.
They also studied blood metabolites—tiny molecules that reflect how the body processes food and maintains normal functions.
Alzheimer’s disease is one of the most common causes of dementia and cognitive decline in older adults.
It has a strong genetic component, with certain variants of the APOE gene greatly increasing risk.
People who carry one copy of the APOE4 variant are three to four times more likely to develop the disease, while those with two copies face about 12 times the risk compared to those without it.
To investigate the role of diet, researchers looked at data from more than 4,200 women in the long-running Nurses’ Health Study and nearly 1,500 men in the Health Professionals Follow-Up Study.
Participants reported their eating habits over decades, gave blood samples for metabolite testing, and provided genetic data. They were tracked for new cases of dementia, and a smaller group underwent regular cognitive testing by phone.
The results showed that people who ate more Mediterranean-style diets had a lower risk of dementia and slower memory decline. The protective effect was strongest in those carrying two APOE4 gene variants, suggesting that healthy eating can help counteract even a high inherited risk.
“These findings suggest that diet influences many important pathways in the body and could be a powerful tool for protecting brain health,” Liu said. She added that while the recommendation applies to everyone, it may be especially important for people at higher genetic risk.
The study did have some limits, as participants were mostly well-educated and of European ancestry.
More research is needed in diverse populations, and most people do not know their genetic risk. Still, the message is clear: adopting a Mediterranean-style diet may be one of the best ways to support long-term brain health.
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