A new study suggests that following a Mediterranean-style diet could lower the risk of dementia, especially for people who carry genes that make them more likely to develop Alzheimer’s disease.
The research was led by scientists from Mass General Brigham, the Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard, and published in the journal Nature Medicine.
The Mediterranean diet includes a lot of fruits, vegetables, whole grains, nuts, fish, and olive oil, with less red meat and processed foods. Earlier research has already shown that this diet can help protect brain health, but this new study looked at how diet affects people with different genetic risks.
Dr. Yuxi Liu, a research fellow and first author of the study, said they chose to study the Mediterranean diet because it’s the only eating pattern that has been proven in a randomized trial to help with brain function.
They also wanted to see how the diet interacts with genetic risk and blood metabolites—tiny molecules in the blood that show how the body processes food.
Alzheimer’s disease, the most common form of dementia, is strongly influenced by genetics. Up to 80% of the risk may come from genes, with one gene in particular, APOE, playing a big role. People with one copy of the APOE4 gene are 3 to 4 times more likely to develop Alzheimer’s, and people with two copies are at 12 times the risk.
The researchers studied long-term health data from 4,215 women in the Nurses’ Health Study and 1,490 men in the Health Professionals Follow-Up Study.
Participants filled out regular food surveys starting in the late 1980s and early 1990s and were followed for over 30 years. The researchers looked at their diets, genetics, blood metabolites, and whether they developed dementia.
The results showed that those who followed a Mediterranean-style diet were less likely to develop dementia and had slower mental decline over time. This benefit was even stronger in people who carried two copies of the high-risk APOE4 gene. The diet seemed to influence key metabolic pathways in the body, which could explain why it helps protect the brain.
These findings suggest that diet can play a powerful role in protecting against cognitive decline—even for people at high genetic risk. Dr. Liu explained that while the Mediterranean diet is helpful for everyone, it could be especially important for those who are genetically more likely to develop Alzheimer’s.
The researchers noted some limitations. Most participants were well-educated and of European ancestry, so the results might not apply to everyone. Also, many people don’t know their APOE gene status, and genetic testing is not yet common in regular dementia screening.
In the future, the researchers hope to explore if changing certain metabolites through diet or other treatments could provide a more personalized way to lower dementia risk.
The study is published in Nature Medicine.
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