A study led by Murdoch University links a Western diet to faster cognitive decline in people with the APOE ε4 gene, a major Alzheimer’s risk factor, after tracking 185 older adults for seven years. The findings highlight the complex relationship between diet, genetics, and brain health.
The research, conducted through the Western Australia Memory Study (WAMS), followed 185 older adults from Perth for more than seven years. Participants were grouped into two dietary patterns: a Western diet, characterized by red and processed meat, chips, pizza, sweets, refined grains, and beer, and a Prudent diet, rich in fruit, vegetables, leafy greens, garlic, and whole grains. None of the participants had diagnosed dementia at the start, but they were tested for genetic susceptibility factors such as the apolipoprotein E (APOE) variant, the strongest common genetic risk factor for Alzheimer’s disease. Researchers found that individuals carrying the APOE ε4 allele experienced a faster decline in attention when adhering to the Western diet, while no significant associations were observed for non-carriers or for the Prudent diet.
Unhealthy Western diet linked to faster cognitive decline in
Our main finding was that among people carrying the APOE ε4 allele, greater adherence to a Western dietary pattern was associated with a faster decline in attention over time,
said Dr. Carolina Blagojevic Castro, lead author and researcher at Murdoch University’s Centre for Healthy Ageing. One of the most interesting findings was that the association with cognitive decline was not seen across the whole group but emerged specifically among APOE ε4 carriers.
The study, which analyzed cognitive changes over seven years, involved participants completing tests to assess attention, memory, executive function, language, recognition memory, and general cognitive ability.
Dr. Blagojevic Castro emphasized the study’s focus on individual differences, noting that diet is particularly interesting because it is often easily modifiable, but people may not respond to dietary patterns in the same way.
She added that the findings reinforced growing evidence that the relationship between diet and brain health is complex, with genetic susceptibility playing a critical role. The research underscores the need for personalized approaches to dietary interventions, as the same diet may affect individuals differently based on their genetic makeup.
Ultra-Processed Foods Hasten Cognitive Decline
A separate study published in the journal JAMA Neurology examined over 10,000 individuals across an 8-year period, revealing that consuming 20% or more of daily calories from ultra-processed foods—such as frozen meals, packaged snacks, and sugary drinks—was linked to a 25% faster decline in executive functions and a 28% faster rate of overall cognitive impairment. Researchers defined ultra-processed foods as those undergoing several industrial processes that can’t be reproduced at home,
including items with flavorings, colorings, and emulsifiers. While this is a study of association, not designed to prove cause and effect, there are a number of elements to fortify the proposition that some acceleration in cognitive decay may be attributed to ultra-processed foods,
said Dr. David Katz, a specialist in preventive and lifestyle medicine and nutrition, adding that the sample size and follow-up period made the findings robust enough that we should conclude ultra-processed foods are probably bad for our brains.
The Australian researchers involved in the larger study noted that the negative impact of ultra-processed foods was less pronounced among individuals with higher overall diet quality. Barbara Cardoso, lead author of the study and a senior lecturer in nutrition, dietetics, and food at Monash University in Melbourne, Australia, highlighted that diets following a Mediterranean style—rich in fish, nuts, olive oil, and vegetables—are associated with reduced cognitive decline. However, the Murdoch-led study focused specifically on genetic susceptibility, while the larger study emphasized the broader risks of ultra-processed foods.
Study links processed foods to targeted domain-specific cognitive decline
Both studies underscore the role of diet in cognitive aging, though they differ in scope and methodology. The Murdoch study, an observational analysis, found no significant associations between the Prudent diet and cognitive decline, though its long-term effects remain unclear. Researchers caution that further research is needed before these findings can be translated into specific dietary recommendations based on genetic risk. There is growing evidence that what we eat can impact our brains as we age,
said Percy Griffin, Ph.D., director of scientific engagement for the Alzheimer’s Association. However, the exact mechanisms and personalized dietary strategies require deeper exploration.
Experts agree that individual responses to diet vary, and the study’s authors advise against broad dietary mandates. What we eat may be one part of a much larger picture of healthy brain aging,
Blagojevic Castro noted. The team plans to expand their work by examining how lifestyle factors—such as physical activity and social engagement—interact with dietary patterns. Approaches to protecting brain health may ultimately need to consider both lifestyle and biological factors rather than assuming that one approach will work equally well for everyone.
Until then, the studies add to a growing body of evidence linking diet to cognitive resilience, particularly for those with genetic vulnerabilities.
Readers are advised that while the evidence suggests a link between unhealthy diets and cognitive decline, these findings do not establish causation. The studies emphasize the importance of consulting qualified professionals for personalized guidance, as individual health needs and genetic profiles vary. The exact mechanisms and personalized dietary strategies require deeper exploration, Griffin said, reinforcing the need for ongoing research and individualized approaches to brain health.