Following a Mediterranean-style diet could help offset the risk of dementia – particularly for people with genetic risks, a new study suggests.
Dementia is thought to be caused by a combination of genetic, lifestyle, and environmental factors. One of the biggest genetic risk factors is a variant in the APOE gene, known as APOE4.
Having one copy of APOE4 triples the risk of Alzheimer’s disease, the most common form of dementia. People with two copies are up to 12 times more likely to develop the disease.
But the study, published in the journal Nature Medicine, suggests that even genetic risk factors can be mitigated.
The US research team found that over a three-decade period, people with Mediterranean-style diets – rich in vegetables, fruits, nuts, whole grains, and low in red and processed meats – were less likely to develop dementia and had slower cognitive decline.
The benefits were strongest for people with two copies of the APOE4 variant.
“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," Yuxi Liu, one of the study’s authors and a researcher at a Harvard University hospital, said in a statement.
"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,” Liu said.
Liu’s team analysed data from more than 4,200 women and nearly 1,500 men over three decades. They tracked the participants’ long-term dietary habits, blood samples, and genetic data, as well as regular cognitive testing for a smaller group of people.
The team chose to study the Mediterranean diet because other research has shown it can boost cognitive wellbeing in old age.
“We wanted to see whether this benefit might be different in people with varying genetic backgrounds, and to examine the role of blood metabolites, the small molecules that reflect how the body processes food and carries out normal functions,” Liu said.
About 25 per cent of people have one copy of APOE4, while two per cent to three per cent have two copies. It’s not entirely clear why the variant raises Alzheimer’s risks, but the APOE protein normally helps transport fats such as cholesterol in the bloodstream and the brain.
The variant appears to disrupt that process and affect how the brain responds to inflammation and the buildup of amyloid plaques, which together could raise Alzheimer’s risks.
Notably, carrying the APOE4 gene variant does not guarantee that someone will develop Alzheimer’s.
The study has some limitations, notably that the participants were mostly well-educated and had European ancestry. Bigger studies with more diverse groups of people would be needed to confirm the findings, the researchers said.
Even so, they suggested that doctors could do more to include genetic and metabolite testing when they assess patients’ Alzheimer’s risks.
“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.
