A new study provides evidence that middle-aged and older adults who consume more ultra-processed foods tend to be less alert and at higher risk of developing dementia. The results of this study show that small daily increases in intake of these foods are associated with measurable decreases in attention span, even if you eat an otherwise healthy diet. The study was published in the journal Alzheimer’s disease and dementia: diagnosis, evaluation, and disease monitoring.
Lead author Barbara Cardoso, a researcher at Monash University’s School of Nutrition, Dietetics and Food and the Victoria Heart Institute, said the study supports a clear link between industrial food production and cognitive decline. Ultra-processed foods are products made through advanced industrial production, typically made from refined raw materials and packed with cosmetic additives such as artificial colors, flavors, and preservatives. These products include everyday items such as soft drinks, packaged salty snacks, and ready-made meals. Essentially, they are anything but fresh, whole foods.
As consumption of these highly manufactured foods increases worldwide, scientists are noticing their association with a variety of negative health effects. Diets high in ultra-processed foods are associated with diseases such as type 2 diabetes, obesity, and cardiovascular disease. These metabolic conditions are known risk factors for cognitive decline, raising concerns about how highly processed diets affect overall brain health over time.
Previous observational studies have found a link between eating highly processed foods and decreased cognitive performance. But big questions remain unanswered in the scientific community. Highly processed foods often substitute nutritious options such as fruits, vegetables, and whole grains. The researchers wanted to understand whether ultra-processed foods have negative effects on the brain simply because they eliminate healthy nutrients, or whether industrial processing itself plays a clear role in cognitive decline.
To investigate this relationship, researchers conducted a cross-sectional study of 2,192 Australian adults aged 40 to 70. All participants had no dementia or neurological disease at the start of the project. Participants were recruited through an online survey platform called the Healthy Brain Project, which targets individuals with a family history of or suspected dementia. This particular age range was chosen because mid-adulthood is when early biological changes associated with neurodegeneration often begin to appear.
Scientists assessed participants’ eating habits using a detailed questionnaire that asked how often they had consumed certain foods and drinks over the past 12 months. After collecting this information, the researchers used a framework known as the Nova system to categorize the reported foods based on their level of industrial processing. To determine the exact percentage of ultra-processed foods in each participant’s daily diet, the research team calculated the total daily calories and total daily weight of the foods each person consumed.
To account for overall diet quality, the researchers also calculated how closely each person adhered to the Mediterranean diet. Measuring this has allowed scientists to separate the effects of food processing from the broader health status of a person’s diet. Participants in this study consumed about 41 percent of their daily energy from ultra-processed foods. This is similar to the Australian national average of 42%.
To measure cognitive function, participants completed a series of computerized card games designed to test a variety of mental skills. These tasks assessed processing speed, visual attention, visual recognition memory, and working memory. Additionally, the scientists used established cardiovascular risk scoring tools to estimate each participant’s risk of developing dementia. They focused on modifiable risk factors, including health conditions such as high blood pressure and obesity that can be actively managed to protect the brain.
When examining cognitive performance, researchers found that higher intake of ultra-processed foods was associated with poorer attention span. “We found that for every 10% increase in the amount of ultra-processed foods a person consumed, there was a clear and measurable decrease in their ability to concentrate,” Cardoso said. “In clinical terms, this led to consistently lower scores on standardized cognitive tests that measure visual attention and processing speed.”
Cardoso gave an example of how this consumption can easily increase. “To put our findings into perspective, a 10% increase in UPF is roughly equivalent to adding a standard bag of chips to your daily diet,” Cardoso said. Based on the modifiable risk score used in the study, higher intakes of these highly processed products were also associated with an increased risk of developing dementia.
Researchers say the degree of food processing plays an important role in harm, even in people who follow a healthy Mediterranean diet, as the negative effects occur regardless of a person’s overall diet quality. Researchers found no direct link between eating ultra-processed foods and memory loss. However, attention span is the basis for many important brain functions, such as learning and problem solving.
The authors proposed several biological mechanisms that may explain how intense food processing negatively affects the brain. “Ultra-processing of food often destroys the natural structure of the food and introduces potentially harmful substances such as artificial additives and processing chemicals,” Cardoso said. These artificial compounds and preservatives are known to destroy the bacterial community that lives within the gastrointestinal tract.
“These additives suggest that the link between diet and cognitive function goes beyond simply not consuming foods known to be healthy, and point to mechanisms related to the degree of food processing itself,” Cardoso said.
Although these findings provide new insights into diet and brain health, there are some limitations that should be considered. This study used a cross-sectional design, meaning that only data from a single time point were examined. Because of this design, researchers cannot prove cause and effect.
While we can’t definitively say that eating ultra-processed foods directly causes cognitive decline, we do know that two variables are involved. Another limitation is that dietary information relies entirely on self-report questionnaires. People don’t always remember exactly what they eat or how much they consume over the course of a year, which can lead to errors in the data.
Furthermore, the study sample consisted primarily of women and individuals with higher educational levels and socio-economic status. This particular demographic means that the findings may not fully apply to the broader general population. Future studies 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 and cognitive decline. Tracking physiological changes in the body and brain can 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, Eurydice Martinez Steele, Barbara Breiner, Xin-Yi Yuan, Lisa Bransby, Hannah Cummins, Yen Yin Lim, and Priscilla Machado.
