Ultra-processed foods may lead to anxiety, hyperactivity in toddlers

A large Canadian study finds toddlers who consume more ultra-processed foods may show slightly higher anxiety, aggression and hyperactivity by age five

Are ultra-processed foods affecting how young children behave? According to scientists, the snacks and ready-to-eat foods toddlers munch on today could shape how they behave a few years later.

 

A new Canadian study titled Ultraprocessed food consumption and behavioral outcomes in Canadian children, published in JAMA Network Open, suggests that higher intake of ultra-processed foods in early childhood may be linked to slightly greater behavioural and emotional difficulties by age five.

 

The researchers at the University of Toronto analysed more than 2,000 children and found that those who consumed more ultra-processed foods at age three had marginally higher scores for behaviours such as anxiety, fearfulness, aggression and hyperactivity two years later. While the changes were modest, researchers say they may still matter at the population level because such foods already make up a large portion of children’s diets.

 

What are ultra-processed foods?

Ultra-processed foods are industrial formulations made mostly from refined ingredients and additives not typically used in home cooking, according to the Nova food classification system, a framework for grouping edible substances based on the extent and purpose of food processing applied to them, developed by researchers at the University of São Paulo, Brazil, in 2009 and adopted by public health systems across the world. These foods often contain emulsifiers, artificial flavours, colourings and ingredients such as high-fructose corn syrup. Common examples include sugar-sweetened or artificially sweetened drinks, packaged snacks and sweets, ready-to-eat or ready-to-heat meals such as fries, and certain packaged breads and cereals.

 

The Nova system groups foods based on how heavily they are processed. In contrast, minimally processed foods (MPFs) include whole fruits, vegetables, grains and fresh meats.

 

According to the researchers, in Canada, ultra-processed foods account for nearly half of the daily calorie intake of preschoolers, making them a dominant part of young children’s diets.

What did the study find about ultra-processed foods and behaviour?

The research drew on data from the Canadian Healthy Infant Longitudinal Development (CHILD) Cohort Study, a large project tracking families from pregnancy through childhood.

 

For this analysis, researchers examined:

• 2,077 children without congenital abnormalities
• Dietary intake at age three, assessed through a detailed 112-item food frequency questionnaire

Behavioural outcomes at age five, measured using the Child Behavior Checklist (CBCL), a validated tool used globally to assess emotional and behavioural problems in children

 

The CBCL generates standardised scores that capture:

• Internalising behaviours such as anxiety, fearfulness and withdrawal
• Externalising behaviours such as aggression or hyperactivity
• Overall behavioural difficulties

The researchers observed that at age three, children in the study consumed an average of about 45.5 per cent of their daily calories from ultra-processed foods.

 

When the same children were assessed at age five, researchers found that higher consumption of ultra-processed foods was linked with slightly higher behavioural difficulty scores.

 

They found that every 10 per cent increase in calories from ultra-processed foods was associated with small increases in behavioural difficulty scores. 

Which ultra-processed foods were most strongly linked to behaviour changes?

The study also analysed different categories of ultra-processed foods to see whether some were more strongly associated with behavioural outcomes.

 

The strongest links were observed with:

• Sugar-sweetened and artificially sweetened beverages
• Packaged breads and cereals
• Ready-to-eat or ready-to-heat foods such as processed mixed dishes

Higher intake of these foods was associated with higher internalising behavioural scores in particular, such as anxiety and fearfulness.

Could healthier food swaps make a difference?

The researchers also simulated what might happen if children replaced some ultra-processed foods with minimally processed alternatives.

 

Their analysis showed that replacing 10 per cent of calories from ultra-processed foods with minimally processed foods was associated with slightly lower behavioural difficulty scores across all domains.

 

Kozeta Miliku, principal investigator and assistant professor of nutritional sciences at the University of Toronto’s Temerty Faculty of Medicine, said in a press statement available on the university website, “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.” 

Why might ultra-processed foods influence behaviour?

Scientists are still trying to understand the biological pathways behind the association. Several mechanisms have been proposed:

• Poor nutrient density: Ultra-processed foods often contain fewer vitamins, minerals and fibre
• High levels of sugar, salt and saturated fat: These nutrients may influence inflammation and brain signalling pathways
• Gut-brain interactions: Diet can affect the gut microbiome, which in turn may influence mood and behaviour
• Chemical exposures: Packaging materials for ultra-processed foods may expose children to substances such as phthalates or bisphenol

Does this mean ultra-processed foods cause behavioural problems?

Not necessarily. The study was observational, meaning it found an association rather than proof of cause and effect.

 

The researchers said that other factors, such as family environment, lifestyle habits and socioeconomic conditions, can also influence children’s behaviour.

What should parents take away from the findings?

Researchers emphasise that the results are not meant to alarm parents but to highlight opportunities for healthier dietary habits early in life.

 

Miliku noted in the statement that convenience foods are often unavoidable for many families.

 

“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. Ultra-processed foods are widely available, affordable and convenient,” she said.

 

She added that even small changes, such as adding a piece of fruit or replacing sugary drinks with water, could help improve children’s overall diet quality and potentially support healthier behavioural development over time. 

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This content is for informational purposes only and is not a substitute for professional medical advice.