Toddlers who consume more ultra processed foods may show slightly greater behavioural and emotional difficulties by the age of five.
A Canadian study, published in JAMA Network Open, analysed data from more than 2,000 children and was led by researchers at the University of Toronto.
It found that greater consumption of ultra-processed foods was associated with small increases in behavioural challenges such as anxiety, fearfulness, aggression, and hyperactivity.
Researchers said the findings highlight the potential benefits of replacing ultra-processed foods with minimally processed foods in early childhood diets.
Kozeta Miliku, principal investigator of the study and an assistant professor of nutritional sciences at the University of Toronto’s Temerty Faculty of Medicine, said the preschool years are critical for child development and also when children begin establishing dietary habits. She said the findings underline the need for early interventions, including professional advice for parents and caregivers, public health campaigns, nutrition standards for childcare providers, and reformulation of some packaged foods.
Ultra-processed foods typically contain high amounts of refined ingredients, additives, and substances rarely used in home cooking. These include emulsifiers, artificial flavours, and high fructose corn syrup. Examples include sugar-sweetened and artificially sweetened beverages, ready-to-eat foods such as French fries or macaroni and cheese, breads, and packaged snacks.
The researchers used data from the CHILD Cohort Study, which tracks pregnant women recruited between 2009 and 2012 in Vancouver, Manitoba, Toronto, and Edmonton. The analysis focused on 2,077 children without congenital abnormalities. Their diets at age three were assessed using a 112-item food frequency questionnaire.
Behavioural outcomes were evaluated at age five using the Child Behaviour Checklist. The study found that every 10 percent increase in calories from ultra-processed foods was linked to small increases in behavioural scores, less than one T-score point across internalising symptoms, externalising behaviours, and total problems.
Replacing 10 percent of calories from ultra-processed foods with minimally processed foods such as fruits and vegetables was linked to modestly lower behavioural scores, suggesting small dietary shifts could support healthier development.