Study shock: Ultra-processed foods may trigger anxiety and aggression in kids

Specifically, the team found that higher ultra-processed food consumption is linked to behavioural and emotional difficulties including anxiety, fearfulness, aggression or hyperactivity.

“The preschool years are critical for child development and it’s also when children begin to establish dietary habits,” says Kozeta Miliku, an assistant professor of nutritional sciences in U of T’s Temerty Faculty of Medicine who was the study’s principal investigator.

“Our findings underscore the need for early-life interventions such as professional advice for parents and caregivers, as well as public health campaigns, nutrition standards for child-care providers and reformulation of some packaged foods.”

Published in JAMA Network Open, the study is the first to examine ultra-processed food consumption and standardized behavioural assessments in kids using detailed, prospective data. It is also among the largest to look at behaviour and mental health in early childhood.

Ultra-processed foods are industrial formulations made largely from refined ingredients and additives not typically used in home cooking. In Canada, they make up nearly half of preschoolers’ calorie intake.

The researchers drew information from the CHILD Cohort Study, a longitudinal, population-based study that recruited pregnant women between 2009 and 2012 and followed their children from before birth through to adolescence at four sites across Canada.

The researchers looked at dietary data from more than 2,000 children who were three years old. Two years later, when the children were five, the team assessed the preschoolers’ scores with the validated Child Behavior Checklist, a widely used measure for emotional and behavioural well-being in children, where higher scores indicate more reported behavioural challenges.

The research team – which included first authors Meaghan Kavanagh, a postdoctoral researcher, and PhD student Zheng Hao Chen –  found that for every 10 per cent increase in calories from ultra-processed foods, children had higher scores on measures of internalizing behaviours such as anxiety and fearfulness and externalizing behaviours such as aggression and hyperactivity, as well as overall behavioural difficulties.

Certain categories of ultra-processed foods showed stronger associations – particularly sugar-sweetened beverages and artificially sweetened drinks. Ready-to-eat and ready-to-heat foods like french fries or macaroni and cheese were linked to higher scores.

In statistical models simulating dietary change, replacing 10 per cent of energy from ultra-processed foods with minimally processed foods such as fruits, vegetables and other whole foods was associated with lower behavioural scores.

Miliku, who is also a researcher at U of T’s Joannah & Brian Lawson Centre for Child Nutrition, says the findings indicate that even a few dietary changes can make a difference in supporting healthier development.

“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,” she says.

Miliku’s interest in the topic was sparked by her everyday observations as a parent.

“As a parent of a toddler, I started noting how often convenience foods appear in children’s diets – sometimes even in places we consider healthy environments,” she says.

A growing body of evidence links ultra-processed foods to increased risks for obesity and cardiometabolic diseases in adults and children. Previous research has also suggested associations between these foods and adverse behaviour and mental health outcomes in adolescents and adults.

“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,” says Miliku.

“Ultra-processed foods are widely available, affordable and convenient. It is important to consider how we can gradually increase whole and minimally processed options when possible.”

Miliku says that even modest changes such as adding a piece of fruit or swapping a sugary drink for water may support children’s emotional and behavioural development over time.

“The goal is to provide evidence that can help families make informed choices."

This study was supported by the Canadian Institutes of Health Research and a Temerty Faculty of Medicine pathway grant.