What we eat may play a role in how the brain ages. But a new study suggests the relationship is not simple, and it may not be the same for everyone.
Researchers in Australia followed 185 older adults and found that people with a common genetic risk factor for Alzheimer’s disease showed faster decline in attention if they more closely followed a Western-style eating pattern. But the finding, published in Nutrients, was limited to attention, not memory or overall thinking ability, and it weakened when researchers removed people who may already have had some cognitive problems at the start of the study.
That means the study does not show that a Western-style diet causes Alzheimer’s disease or that changing your diet would prevent it.
The participants were part of the Western Australia Memory Study. They were about 71 years old on average and did not have diagnosed dementia when the research began.
Researchers asked participants about the foods they usually ate, then grouped those habits into two broad patterns.
The Western-style pattern included more foods such as red and processed meats, chips, sweets, refined grains, pizza and beer. The Prudent pattern included more vegetables, fruit, leafy greens, garlic and whole grains.
These labels describe overall eating patterns, not individual foods. The study cannot tell us that any one food was responsible for the results.
Participants also completed a series of tests over several years to track changes in areas such as attention, memory, language and other thinking skills.
For the group as a whole, researchers found no clear link between either dietary pattern and cognitive decline.
The result appeared only when they looked separately at people who carried APOE ε4, a gene variant associated with a higher risk of Alzheimer’s disease.
Among those participants, greater adherence to the Western-style diet was linked with a faster decline in attention. Researchers did not find the same link in people without the variant. They also did not find significant links with memory, language or several other areas of thinking.
The healthier Prudent pattern was not linked with slower cognitive decline.
That matters because the study does not support a simple message that one diet “hurts” the brain while another “protects” it.
APOE ε4 is a risk factor, not a diagnosis. Carrying the variant does not mean someone will develop Alzheimer’s disease, and many people who develop Alzheimer’s do not carry it.
The biggest caution came when researchers took a closer look at participants who may already have had some cognitive impairment at the start.
After those people were excluded, the link between the Western-style diet and attention decline was no longer statistically significant.
That makes the result much less certain. It also raises an important question: Were eating habits influencing brain changes, or could early changes in thinking have influenced how people ate or how accurately they remembered their diet?
Because the study was observational, it cannot answer that.
The research also had several other limitations. It included only 185 people, and just 57 carried APOE ε4. Diet was measured only once, so the study could not track whether people changed how they ate over the years. The number of participants also dropped over time, with only 36 completing the final round of cognitive testing.
Even so, the study adds to a growing question in brain-health research: whether lifestyle factors may affect people differently depending on their biology.
“What we eat may be one part of a much larger picture of healthy brain ageing,” lead author Carolina Blagojevic Castro said in a news release.
For now, the findings are best seen as an early clue rather than a reason to change your diet based on genetic risk.
The study suggests there may be a connection between Western-style eating and attention decline in some people with higher Alzheimer’s risk, but larger studies are needed to know whether that connection is real, how important it is and whether changing eating habits would make a difference.
One author was supported by the Government of Western Australia through the Premier’s Science Fellowship Program. Several authors reported roles with SMarT Minds WA, and two reported receiving reimbursements or research support from pharmaceutical or nutraceutical companies, including Alector, Alnylam Pharmaceuticals and Biogen.