People with Alzheimer’s risk gene may want to rethink Western diet - Newsweek

People who carry the strongest common genetic risk factor for Alzheimer’s disease may experience faster decline in attention if they follow a Western-style diet, according to new research.

The study, published in the journal Nutrients, followed 185 older adults without dementia from the Western Australia Memory Study and examined whether dietary habits were linked to changes in cognitive performance over time.

Researchers tracked participants for up to 7.5 years and analyzed the results according to whether they carried the APOE ε4 gene variant, a well-established genetic risk factor for Alzheimer's disease.

They found that among APOE ε4 carriers, greater adherence to a Western dietary pattern was associated with a faster decline in attention.

No significant links were observed for a healthier "Prudent" dietary pattern or among participants who did not carry the risk gene.

The Western dietary pattern is typically characterized by higher intakes of processed foods, refined grains, red and processed meats, fried foods and sugary products.

The Prudent pattern emphasizes foods such as fruits, vegetables, fish and whole grains.

However, the researchers cautioned that the findings do not prove that diet caused the cognitive decline.

The study was observational, meaning it can identify associations but cannot establish cause and effect.

The association also became weaker after researchers excluded participants who may already have had subtle cognitive impairment at the start of the study.

"I would be cautious about using our findings to guide individual decisions about genetic testing at this stage," lead author Dr. Carolina Blagojevic Castro, a postdoctoral research fellow in nutrition and healthy aging, told Newsweek.

"APOE ε4 is an important genetic risk factor for Alzheimer’s disease, but it is not deterministic,” Castro said. “Carrying the allele does not mean that someone will develop Alzheimer’s disease, and our study was not designed to evaluate the clinical utility of APOE testing."

Castro said the study does not provide enough evidence to support genetic testing or personalized recommendations based on APOE status.

"For asymptomatic individuals, I therefore would not recommend APOE testing on the basis of our findings alone," she added.

Anyone considering APOE testing should do so with medical and genetic counseling to fully understand what the results can and cannot tell them, Castro said.

The study also cannot determine whether changing dietary habits later in life could help slow cognitive decline.

Castro pointed to broader research suggesting that protecting brain health may require a combination of approaches.

She highlighted the landmark FINGER trial, which found cognitive benefits from a multidomain intervention involving dietary guidance, physical activity, cognitive training and management of vascular and metabolic risk factors.

"Taken together, the evidence supports a multidomain view of cognitive aging rather than attributing risk or protection to a single food or behavior," she said.

Independent expert Caghan Kizil, Ph.D., professor of neurological sciences at Columbia University's Department of Neurology and the Taub Institute for Research on Alzheimer's Disease and the Aging Brain, said the findings are intriguing but should be interpreted with caution.

"These findings give researchers a lead, not families a prescription," Kizil told Newsweek.

He noted that the study did not directly measure Alzheimer's disease or dementia risk but instead tracked changes in cognitive test performance.

Among the 57 people who carried the APOE ε4 gene, those who followed a Western diet showed a faster decline in attention.

However, the link became weaker when researchers excluded participants who may already have had cognitive problems at the start of the study.

"The findings should therefore be considered hypothesis-generating, rather than evidence that diet modifies genetic risk for Alzheimer’s disease," Kizil said.

He also highlighted limitations including the relatively small number of APOE ε4 carriers, substantial participant attrition, and the fact that diet was measured only once at the start of the study using self-reported questionnaires.

Kizil said the study should not be interpreted as evidence that avoiding a Western diet can counteract inherited risk.

"Maintaining a healthy diet remains sensible for cardiovascular and metabolic health, both of which are relevant to healthy brain aging," he said. "But that advice comes from the broader evidence base, not from this single, limited association involving attention in a small genetic subgroup. This study is a reason for further research, not a basis for individualized dietary recommendations."

Blagojevic Castro, C., Gardener, S. L., Jahan, F., Chen, J., Brown, B. M., Loo, R. L., Taddei, K., Rainey-Smith, S. R., Weinborn, M., Reis, A. C. R. d., Garg, M. L., Martins, R. N., & Sohrabi, H. R. (2026). Dietary Patterns and Cognitive Decline in Older Adults: Findings from the Western Australia Memory Study. Nutrients, 18(16), 2592. https://doi.org/10.3390/nu18162592