Canadian Preschoolers Who Ate More Ultraprocessed Foods Had Worse Behavioral Scores by Age 5

The early years of childhood are a period of rapid neurological development, and accumulating evidence suggests that diet during this window does more than support physical growth. A cohort study of Canadian preschoolers now adds behavioral development to the list of outcomes associated with ultraprocessed food consumption - finding that children who ate more of these foods showed worse behavioral and emotional symptom scores by the time they turned five.

The work, published in JAMA Network Open, was led by Kozeta Miliku at the University of Toronto and focuses on a population-based cohort of Canadian children followed from infancy through early childhood.

What Was Measured

The study used validated tools to assess dietary patterns and behavioral outcomes in preschool-age children. Ultraprocessed foods (UPF) are defined using the NOVA classification system - a framework that categorizes foods based on the degree and purpose of their industrial processing rather than their nutrient content alone. UPFs include ready-to-eat snacks, packaged bread and cereals, flavored dairy products, reconstituted meat products, and sugar-sweetened beverages. They are distinguished from processed foods (such as canned vegetables or cheese) by the use of industrial processes and additives - emulsifiers, flavor enhancers, colorants, and stabilizers - that are absent from minimally processed alternatives.

Behavioral and emotional outcomes were assessed using standardized parent-report instruments measuring dimensions including hyperactivity, emotional symptoms, conduct problems, and peer relationship difficulties. The analysis adjusted for socioeconomic factors, maternal education, family income, and other variables that could independently influence both dietary patterns and behavioral outcomes.

The Association

Higher UPF intake was associated with adverse behavioral and emotional symptom scores at age 5, with the relationship persisting after statistical adjustment for the confounding variables included in the analysis. Children with higher UPF intake showed measurably worse outcomes across behavioral dimensions compared to those whose diets contained more minimally processed foods.

The finding is observational - the study design cannot establish that ultraprocessed food consumption caused the behavioral differences observed. Children who eat more UPFs may differ from those who eat fewer in ways that the available data cannot fully capture. Reverse causation is also possible: children with certain behavioral tendencies may be harder to feed, leading caregivers to rely more heavily on convenient, packaged foods. The study's authors acknowledge these limitations and frame the findings as supporting the case for early dietary interventions rather than establishing definitive causal claims.

Mechanisms and Context

Several biological pathways could plausibly connect early dietary patterns to behavioral development. The gut microbiome is one candidate: diet substantially shapes microbial community composition, and gut-brain axis research suggests microbiome disruption in early life affects neurodevelopmental trajectories. Nutrient density is another: UPFs tend to be low in fiber, micronutrients, and omega-3 fatty acids relative to minimally processed alternatives, and several of those nutrients are involved in brain development and neurological function during early childhood.

The preschool period is also a window during which dietary habits are being established. Patterns of food preference and eating behavior formed in early childhood are known to track into later life, which means the implications of early UPF intake may extend beyond age 5.

Policy Implications

The authors argue that the findings support ongoing policy efforts to promote minimally processed food consumption in early childhood, including food labeling initiatives, early childhood nutrition standards, and programs that support access to fresh and minimally processed foods for families with young children. The study was conducted in Canada, where food environments and dietary patterns may differ from those in other countries, though UPF consumption in childhood is high across most high-income nations.

The cohort study design provides a stronger basis for inference than a cross-sectional snapshot, but a randomized trial - difficult to conduct for dietary patterns across years of childhood - would be required to establish causality definitively. The current evidence is consistent with the hypothesis that replacing UPFs with minimally processed alternatives during the preschool years could support more positive behavioral development trajectories.