New research finds that ultra-processed foods reduce attention span measurably — even in people who otherwise eat well — while a companion study shows that diet quality, not food group, is the key variable in brain health and dementia risk.
Most people think of ultra-processed foods as a trade-off — not ideal, but manageable within an otherwise healthy diet. New research from Monash University, the University of São Paulo, and Deakin University, published this month in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, makes a fairly persuasive case that the trade-off is steeper than most of us have been accounting for. The study examined the diets and cognitive health of more than 2,100 Australian adults who were middle-aged or older and found that rising ultra-processed food consumption is tied to measurable drops in attention span — along with elevated dementia risk factors — regardless of what else is on the plate.
The numbers are notable: for every 10 percent increase in ultra-processed food consumed, researchers at Monash measured a distinct drop in visual attention and processing speed. “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,” lead author Dr. Barbara Cardoso, from the Department of Nutrition, Dietetics and Food and the Victorian Heart Institute at Monash University, said in a statement. “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 standardised cognitive tests measuring visual attention and processing speed.”
The participants consumed roughly 41 percent of their daily energy from UPFs, closely mirroring Australia’s national average of 42 percent — a reminder that this level of intake is the norm rather than the exception. The category is broad: soft drinks, packaged snacks, ready-made meals, anything engineered far from its original whole-food state.
What makes the findings harder to dismiss is the “regardless of what else you eat” qualifier. The cognitive damage occurred even in people following a Mediterranean dietary pattern — widely considered one of the more brain-protective eating styles available. “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.”
The limits of eating well
W. Taylor Kimberly, a neurologist at Massachusetts General Hospital, told the American Academy of Neurology that higher UPF consumption was associated with elevated risk of both stroke and cognitive impairment, even after accounting for other dietary factors. The mechanisms amount to a cascade: artificial additives disrupt gut microbiome composition, which drives systemic inflammation; insulin resistance impairs the brain’s glucose metabolism; and the structural breakdown that occurs during processing strips away compounds that support neurological function — compounds that never appear on a nutrition label.
Attention is not a peripheral cognitive function. It underpins learning, reasoning, and problem-solving, and when it erodes, other functions tend to follow. That this degradation showed up in people who had not yet developed dementia — who were, by clinical measures, cognitively intact — is the more significant part of the finding. These are not end-stage effects. They are already present.
What your brain actually wants to eat
A companion study published April 8 in Neurology provides useful contrast. Researchers tracked nearly 93,000 adults across five ethnic groups for an average of 11 years and found that the quality of a plant-based diet — not just whether someone ate plant foods — was directly tied to dementia risk. Those following the highest-quality plant-based diets, built around whole grains, vegetables, fruits, nuts, and legumes, had a 12 percent lower risk of developing dementia overall. Those who leaned into an unhealthful plant-based pattern built on refined grains, fruit juices, and added sugars had a 25 percent higher risk by the study’s end.
“We found that adopting a plant-based diet, even starting at an older age, and refraining from low-quality plant-based diets were associated with a lower risk of Alzheimer’s and other dementias,” lead researcher Song-Yi Park said in a statement. “Our findings highlight that it is important not only to follow a plant-based diet, but also to ensure that the diet is of high quality.”
Her co-author Unhee Lim offered what amounts to the most actionable note from either study: “It’s never too late to start eating healthy to lower the risk of Alzheimer’s disease and related dementias.”
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