Daily ultra-processed foods linked to dementia risk, even with healthy diet

A small bag of potato chips. That's all it takes—a single ten-percent increase in daily ultraprocessed food consumption—to measurably shrink your attention span and nudge your dementia risk upward, even if the rest of your diet looks pristine. This is the finding of a new study published in Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring, one that arrives amid a growing pile of evidence suggesting that how food is made matters as much as what food you eat.

Researchers at Monash University in Melbourne recruited more than 2,100 Australians between 40 and 70 years old and asked them to keep detailed food diaries spanning a full year. The participants also underwent cognitive testing to measure attention and processing speed. None had dementia at the start. What emerged was stark: for every ten-percent bump in ultraprocessed food intake, people showed a distinct and measurable decline in their ability to concentrate. When researchers translated this into clinical terms, it meant consistently lower scores on standardized tests of visual attention and how quickly the brain could handle new information.

The mechanism is not mysterious. Ultraprocessed foods—those industrial creations stripped down to molecular components, then reassembled with artificial colors, flavors, and emulsifiers—are calorie-dense but nutrient-poor. They flood the body with sugar, salt, and fat while starving it of the essential compounds a healthy brain needs. In the United States, these foods now account for 53 percent of all calories consumed by adults, and nearly 62 percent of children's energy intake, according to the CDC. In Australia, roughly 42 percent of the typical diet comes from ultraprocessed sources.

What makes this research particularly striking is that the cognitive damage persists regardless of whether someone otherwise follows a Mediterranean diet—one of the most celebrated eating patterns for brain health. The association held even among people who ate plenty of vegetables and whole grains. This suggests the problem is not simply about replacing good foods with bad ones, but about the ultraprocessed foods themselves. Barbara Cardoso, the study's lead author and a senior lecturer in nutrition at Monash, explained that the decline in attention capacity translated to a measurable increase in dementia risk when projected over twenty years. Each ten-percent increase in daily ultraprocessed food consumption correlated with a 0.24-point rise on a seven-point dementia risk scale.

The findings align with a parallel study published in January by W. Taylor Kimberly at Harvard Medical School, which found that a ten-percent increase in ultraprocessed food consumption raised the risk of cognitive decline by 16 percent—again, independent of overall diet quality. Kimberly's work also offered a glimmer of hope: replacing ultraprocessed foods with whole and minimally processed alternatives over five to six years was associated with a 12 percent lower risk of cognitive decline. An April study reinforced this message, showing that adults in their 50s and 60s who eliminated many unhealthy foods over a decade had an 11 percent lower risk of Alzheimer's disease and dementia compared to those whose diets remained unchanged.

The damage ultraprocessed foods inflict appears to work through multiple pathways. They disrupt the endocrine system and alter the gut microbiota—the trillions of bacteria that influence everything from digestion to mood to brain function. They also elevate cardiovascular risk factors like diabetes, high blood pressure, obesity, and elevated LDL cholesterol, all of which are known to harm cognitive health indirectly. A comprehensive 2024 review of 45 studies covering roughly ten million people found that each ten-percent increase in ultraprocessed food consumption raised the risk of death from cardiovascular disease by about 50 percent and the risk of common mental disorders by a similar margin. The same increase was linked to a 55 percent higher risk of obesity, 41 percent for sleep disorders, 40 percent for type 2 diabetes, and 20 percent for depression.

Cardoso emphasizes that middle age represents a critical window. This is the moment, she argues, when people can still modify risk factors before the neurological changes that underlie dementia take hold. The brain's decline in attention and processing speed may seem subtle—a slight difficulty concentrating, a moment's lag in understanding—but these are the early signs of a larger cognitive erosion. The good news is that the damage is not irreversible if caught early enough. The bad news is that the average diet in wealthy nations is already saturated with these foods, and the clock is ticking.