A long-term study has found that people who follow a Mediterranean-style diet are less likely to develop dementia and experience slower cognitive decline, even if they carry genetic risk factors for Alzheimer’s disease.
The research, published in Nature Medicine, highlights the role of diet in offsetting the risks associated with APOE4, a genetic variant known to increase the likelihood of Alzheimer’s. Individuals with one copy of the variant face a threefold risk, while those with two copies are up to 12 times more likely to develop the condition.
Despite these risks, the study shows that diet can make a significant difference. Researchers from a Harvard University hospital analyzed data spanning more than three decades from over 4,200 women and nearly 1,500 men. Participants’ dietary habits, blood samples, and genetic data were examined, with a smaller group also undergoing regular cognitive assessments.
The findings suggest that individuals who consistently ate a Mediterranean-style diet—rich in vegetables, fruits, nuts, whole grains, and low in red and processed meats—were less likely to develop dementia and showed slower rates of cognitive decline compared to those who did not.
“These findings suggest that dietary strategies, specifically the Mediterranean diet, could help reduce the risk of cognitive decline and stave off dementia by broadly influencing key metabolic pathways,” said Yuxi Liu, one of the study’s authors. “This recommendation applies broadly, but it may be even more important for individuals at a higher genetic risk, such as those carrying two copies of the APOE4 genetic variant.”
The research team noted that the APOE protein normally helps transport fats like cholesterol in the bloodstream and brain. The APOE4 variant appears to disrupt that process, affecting how the brain handles inflammation and the buildup of amyloid plaques—two factors strongly linked to Alzheimer’s disease. Still, carrying the variant does not mean someone will inevitably develop the illness.
About one-quarter of people have one copy of APOE4, while two to three percent carry two copies.
While the study strengthens the case for diet as a preventive tool, the researchers acknowledged limitations. The participants were mostly well-educated and of European ancestry, which means further studies in more diverse populations are needed to confirm the findings.
Even so, the authors said the results could change how doctors assess Alzheimer’s risks, suggesting that genetic and metabolite testing may become a greater part of future evaluations.
“In future research, we hope to explore whether targeting specific metabolites through diet or other interventions could provide a more personalised approach to reducing dementia risk,” Liu said.
The Mediterranean diet has previously been linked to improved cardiovascular health and longer lifespans. This latest study adds to growing evidence that it could also play a key role in protecting the brain from age-related decline.
