- Higher intake of ultra-processed foods in the preschool years has been linked with more behavioural and emotional difficulties later in childhood.
- The study found associations with anxiety, fearfulness, aggression and hyperactivity.
- It does not prove cause and effect, but it adds to growing concern about how heavily processed diets may affect children’s health beyond weight alone.
Researchers at the University of Toronto have found a link between ultra-processed food intake in early childhood and later behavioural and emotional difficulties.
The study was published in JAMA Network Open.
It used data from more than 2,000 children taking part in the CHILD Cohort Study in Canada.
The researchers looked at diet at age three.
They then assessed behaviour and emotional wellbeing at age five using the Child Behavior Checklist, a validated assessment tool.
They found that higher intake of ultra-processed foods was associated with higher scores for internalising behaviours such as anxiety and fearfulness.
It was also linked with higher scores for externalising behaviours such as aggression and hyperactivity.
Higher overall behavioural difficulty scores were also seen.
The study found that for every 10% increase in calories coming from ultra-processed foods, behavioural scores tended to worsen.
Some foods appeared to show stronger links than others.
These included sugary drinks, artificially sweetened drinks and ready-to-eat or ready-to-heat foods such as chips and macaroni cheese.
The researchers also modelled what might happen if part of that intake was replaced.
Replacing 10% of energy from ultra-processed foods with minimally processed foods was associated with lower behavioural scores.
- Ultra processed foods are engineered like cigarettes
- Ultra-processed foods engineered to be addictive
- High intake of ultra-processed foods linked to higher death risk in cancer survivors
That included foods such as fruit, vegetables and other whole foods.
This is an observational study, so it cannot prove that ultra-processed foods directly caused the behavioural problems.
But it is one of the largest studies to look at this question in early childhood and it used prospective data rather than one-off snapshots.
That gives the findings more weight than much of the earlier evidence in this area.
The authors say the results support early intervention.
That could include advice for parents and carers, better nutrition standards in childcare settings and reformulation of heavily processed packaged foods.
There is also an important real world point here.
Ultra-processed foods are cheap, convenient and widely available, and many families rely on them at least some of the time.
So this is not about blaming parents.
It is about recognising that even modest shifts towards less processed foods may support healthier development over time.
Journal reference: Kavanagh ME, et al. Ultraprocessed Food Consumption and Behavioral Outcomes in Canadian Children. JAMA Network Open. 2026.
