Eating patterns in the preschool years may be linked to later emotional and behavioral development. A new prospective study of more than 2,000 Canadian children found that higher intake of ultraprocessed foods at age 3 was associated with more reported behavioral difficulties at age 5.
The study, published in JAMA Network Open, was observational, meaning it cannot prove that ultraprocessed foods cause behavior problems. It does suggest a consistent association that researchers say warrants closer attention.
“The preschool years are critical for child development, and it’s also when children begin to establish dietary habits,” said Kozeta Miliku, an assistant professor of nutritional sciences at the University of Toronto and the study’s principal investigator.
Researchers used data from the CHILD Cohort Study, which has followed families from pregnancy through childhood at four sites across Canada. When children were age 3, caregivers reported dietary intake. Researchers calculated the percentage of calories coming from ultraprocessed foods, which are industrial formulations made largely from refined ingredients and additives not typically used in home cooking.
Two years later, when the children were age 5, caregivers completed the Child Behavior Checklist, a standardized and widely used assessment tool. Higher scores indicate more reported emotional and behavioral challenges.
For every 10% increase in calories from ultraprocessed foods at age 3, children had higher scores for internalizing behaviors such as anxiety and fearfulness, externalizing behaviors such as aggression and hyperactivity and overall behavioral difficulties.
Certain categories showed stronger associations, particularly sugar-sweetened beverages and artificially sweetened drinks. Ready-to-eat and ready-to-heat items such as French fries and macaroni and cheese were also linked to higher scores.
In statistical models simulating dietary change, replacing 10% of energy from ultraprocessed foods with minimally processed foods such as fruits and vegetables was associated with lower behavioral scores.
“Our findings suggest that even modest shifts toward minimally processed foods, like whole fruits and vegetables, in early childhood may support healthier behavioural and emotional development,” Miliku said.
What the study did not show is equally important. It did not test a dietary intervention, and it did not demonstrate that reducing ultraprocessed foods will directly improve a child’s behavior. Observational studies can be influenced by many factors, including household stress, sleep patterns, screen time, income and broader lifestyle differences that may also affect behavior.
Ultraprocessed foods are widely consumed and often convenient and affordable. In Canada, they account for nearly half of preschoolers’ calorie intake. Researchers emphasized that families face real constraints.
“Parents are doing their best and not all families have access to single-ingredient foods, or the tools and time needed to incorporate them into their families' diets,” Miliku said. “Ultra-processed foods are widely available, affordable and convenient.”
The findings add to a growing body of research linking ultraprocessed food intake to various health outcomes. For families, the takeaway is not elimination but awareness. Small shifts, such as adding a piece of fruit or replacing a sugary drink with water, may be reasonable starting points when possible.
“The goal is to provide evidence that can help families make informed choices,” Miliku said.
This study was funded by the Canadian Institutes of Health Research and a Temerty Faculty of Medicine pathway grant.