Researchers from Monash University, the University of São Paulo, and Deakin University analyzed dietary and cognitive data from more than 2,100 middle-aged and older Australian adults who did not have dementia. Their findings were published in Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring, a journal of the Alzheimer's Association.

Ultra-Processed Foods and Attention Span

The study found that even modest increases in ultra-processed food consumption were associated with measurable declines in attention and mental processing speed.

Lead author Dr. Barbara Cardoso, from Monash University's Department of Nutrition, Dietetics and Food and the Victorian Heart Institute, said the results add to growing evidence linking highly processed foods to poorer brain health.

"To put our findings in perspective, a 10 percent increase in UPFs is roughly equivalent to adding a standard packet of chips to your daily diet," Dr. Cardoso said.

"For every 10 percent increase in ultra-processed food a person consumed, we saw a distinct and measurable drop in a person's ability to focus.

"In clinical terms, this translated to consistently lower scores on standardized cognitive tests measuring visual attention and processing speed."

Participants in the study obtained about 41 percent of their daily calories from ultra-processed foods, nearly matching the Australian national average of 42 percent.

Why Food Processing May Matter

Ultra-processed foods (UPFs) include products such as soft drinks, packaged salty snacks, and ready-made meals. Unlike fresh or minimally processed foods, these products undergo extensive industrial processing.

One of the study's most notable findings was that the negative effects on attention appeared regardless of a person's overall diet quality. Even participants who generally followed a healthy Mediterranean-style diet showed the same relationship between greater ultra-processed food intake and poorer focus.

According to the researchers, this suggests that the level of processing itself may play an important role.

"Food ultra-processing often destroys the natural structure of food and introduces potentially harmful substances like artificial additives or processing chemicals," Dr. Cardoso said.

"These additives suggest the link between diet and cognitive function extends beyond just missing out on foods known as healthy, pointing to mechanisms linked to the degree of food processing itself."

Connection to Dementia Risk Factors

The researchers also found that higher consumption of ultra-processed foods was associated with an increase in known dementia risk factors. These include conditions such as obesity and high blood pressure, both of which can be managed to help support long-term brain health.

While the study did not identify a direct link between ultra-processed foods and memory loss, the researchers note that attention is a fundamental cognitive function. It plays a critical role in learning, problem-solving, and many other mental tasks.

Because attention serves as the foundation for so many aspects of thinking, declines in focus may represent an important early warning sign of broader cognitive changes.

Research Team and Funding

The study was led by Dr. Barbara Cardoso. Co-authors included Dr. Lisa Bransby, Hannah Cummins, Professor Yen Ying Lim, and Xinyi Yuan from Monash University; Dr. Euridice Martinez Steele from the University of São Paulo; and Dr. Barbara Brayner and Dr. Priscila Machado from Deakin University.

The research used data from the Healthy Brain Project, which is supported by the National Health and Medical Research Council (NHMRC), the Alzheimer's Association, the Dementia Australia Research Foundation, the Bethlehem Griffiths Research Foundation, the Yulgilbar Alzheimer's Research Program, the National Heart Foundation of Australia, and the Charleston Conference for Alzheimer's Disease. Dr. Euridice Martinez Steele was funded by FAPESP (2023/16144-3), Dr. Priscila Machado by an NHMRC Emerging Leadership Fellowship (APP2034008), and Professor Yen Ying Lim by an NHMRC Career Development Fellowship (GNT1162645) and an Emerging Leadership Grant (GNT2009550).