Ultra-processed foods linked to poorer attention and higher dementia risk, even if your diet is otherwise healthy

A new study provides evidence that middle-aged and older adults who consume higher amounts of ultra-processed foods tend to have poorer attention and a higher risk of developing dementia. The findings demonstrate that a slight daily increase in a person’s intake of these foods is linked to a measurable drop in attention span, even if someone otherwise eats healthy. The research was published in the journal Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.

Barbara Cardoso, lead author and a researcher at the Department of Nutrition, Dietetics and Food and the Victorian Heart Institute at Monash University, noted that the study reinforces a distinct connection between industrial food manufacturing and cognitive decline. Ultra-processed foods are products created through intense industrial manufacturing, typically made from refined ingredients and packed with cosmetic additives like artificial colors, flavors, and preservatives. These items include everyday products like soft drinks, packaged salty snacks, and ready-made meals. Essentially, they are anything that is not a fresh whole food.

As the consumption of these heavily manufactured foods has increased globally, scientists have noted associations with a wide variety of negative health outcomes. Diets heavy in ultra-processed products are linked to conditions such as type 2 diabetes, obesity, and cardiovascular disease. Because these metabolic conditions are known risk factors for cognitive decline, concerns have emerged regarding how a highly processed diet might influence overall brain health over time.

Previous observational studies have found connections between eating highly processed foods and experiencing worse cognitive performance. However, a major question has remained unanswered in the scientific community. Highly processed foods often take the place of nutrient-dense options like fruits, vegetables, and whole grains. Researchers wanted to understand if ultra-processed foods negatively impact the brain simply because they crowd out healthy nutrients, or if the industrial processing itself plays a distinct role in cognitive decline.

To explore this relationship, researchers conducted a cross-sectional study involving 2,192 Australian adults between the ages of 40 and 70. All participants were free of dementia and neurological conditions at the start of the project. The participants were recruited through an online research platform called the Healthy Brain Project, which targeted individuals who had a known or suspected family history of dementia. This specific age range was selected because middle adulthood is a time when the early biological changes associated with neurodegeneration often begin to emerge.

The scientists assessed the dietary habits of the participants using a detailed questionnaire that asked how often they consumed specific foods and beverages over the previous twelve months. After collecting this information, the researchers used a framework known as the Nova system to classify the reported foods based on their level of industrial processing. The team calculated the total daily calories and the total daily weight of the food consumed by each person to determine the exact percentage of ultra-processed foods in each participant’s daily diet.

To account for overall diet quality, the researchers also calculated how closely each person adhered to a Mediterranean diet. By measuring this, the scientists could isolate the effects of food processing from the broader healthiness of a person’s diet. The participants of the study consumed roughly 41 percent of their daily energy from ultra-processed foods. This closely mirrors the national Australian average of 42 percent.

To measure cognitive function, the participants completed a series of computerized card games designed to test different mental skills. These tasks assessed processing speed, visual attention, visual recognition memory, and working memory. Additionally, the scientists estimated each participant’s risk of developing dementia using an established cardiovascular risk scoring tool. They focused on modifiable risk factors, which include health conditions such as high blood pressure or obesity that can actively be managed to protect the brain.

When looking at cognitive performance, the researchers found that higher consumption of ultra-processed food was associated with poorer attention. “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,” Cardoso said. “In clinical terms, this translated to consistently lower scores on standardized cognitive tests measuring visual attention and processing speed.”

Cardoso provided a practical example of how easily this consumption can increase. “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,” Cardoso said. Higher intake of these heavily processed products was also linked to an increased risk of developing dementia, based on the modifiable risk score used in the study.

Because the negative effects take place regardless of a person’s overall diet quality, even for people following a healthy Mediterranean diet, researchers say the degree of food processing plays an important role in the damage. The researchers did not find a direct association between ultra-processed food consumption and memory loss. However, attention span is the foundation for many important brain operations, such as learning and problem-solving.

The authors proposed several biological mechanisms that might explain how intense food processing harms the brain. “Food ultra-processing often destroys the natural structure of food and introduces potentially harmful substances like artificial additives or processing chemicals,” Cardoso said. These artificial compounds and preservatives are known to disrupt the community of bacteria living in the digestive tract.

“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,” Cardoso said.

While these findings provide new insights into diet and brain health, there are a few limitations to consider. The study used a cross-sectional design, meaning it only looked at data from a single point in time. Because of this design, the researchers cannot prove cause and effect.

It is not possible to say with absolute certainty that eating ultra-processed foods directly causes cognitive decline, only that the two variables are connected. Another limitation is that the dietary information relied entirely on self-reported questionnaires. People do not always remember exactly what they ate or how much they consumed over a full year, which can introduce errors into the data.

Additionally, the study sample was largely made up of women and individuals with higher levels of education and socioeconomic status. This specific demographic makeup means the findings might not fully apply to the broader general population. Future research will need to follow participants over many years to see how cognitive function changes over time.

Scientists also plan to incorporate brain imaging and biological markers to better understand the physical pathways linking industrial food processing to cognitive decline. Tracking physiological changes in the body and brain will help medical professionals create targeted dietary guidelines for dementia prevention.

The study, “Ultra-processed food intake, cognitive function, and dementia risk: A cross-sectional study of middle-aged and older Australian adults,” was authored by Barbara R. Cardoso, Euridice Martinez Steele, Barbara Brayner, Xinyi Yuan, Lisa Bransby, Hannah Cummins, Yen Ying Lim, and Priscila Machado.