Ultraprocessed Foods Linked to Behavioral Issues in Preschoolers

Preschoolers who consume a diet higher in ultraprocessed foods may exhibit more behavioral problems, according to research published this week in JAMA Network Open. The Canadian study, tracking nearly 2,100 children, found a correlation between the percentage of daily energy intake from these foods and scores on measures of internalizing and externalizing behaviors – encompassing anxiety, aggression, and hyperactivity – at age five.

Ultraprocessed foods, defined as formulations made mostly or entirely from substances derived from foods and additives, and not typically made in kitchen settings, now constitute a substantial portion of many young children’s diets. In Canada, the study authors note, these foods account for nearly half of the daily energy intake of preschoolers. The research doesn’t establish a causal link, but it adds to a growing body of evidence suggesting a connection between dietary patterns and child development.

Study Details and Findings

The prospective CHILD cohort study, conducted between 2011 and 2018, followed children in central and western Canada. Researchers assessed ultraprocessed food consumption at age three using a 112-item questionnaire, calculating it as a percentage of total energy intake. Behavioral outcomes were then measured at age five using the Child Behavior Checklist (CBCL), a standardized tool completed by caregivers. Higher CBCL scores indicate more pronounced behavioral difficulties.

The study population comprised 2,077 children, with a slight majority (52.6%) being male. The ethnic breakdown was approximately 66% White, 23% multiracial, and 11% identifying with other ethnic groups. On average, preschoolers consumed 45.5% of their daily energy from ultraprocessed foods. Corresponding CBCL scores averaged 44.6 for internalizing behaviors, 39.6 for externalizing behaviors, and 41.2 overall.

For every 10% increase in energy derived from ultraprocessed foods, researchers observed statistically significant increases in CBCL scores for internalizing behaviors (β = 0.81; 95% CI, 0.43-1.19), externalizing behaviors (β = 0.47; 95% CI, 0.08-0.87), and total behavior (β = 0.64; 95% CI, 0.27-1.01). While these effect sizes were modest, they suggest a potential association between early dietary habits and behavioral outcomes.

What are Ultraprocessed Foods?

Defining “ultraprocessed” can be tricky. The NOVA classification system, used in this study and increasingly in nutritional research, categorizes foods based on the extent and purpose of processing. Previous research has linked higher consumption of these foods to increased risk of prediabetes in young adults. Ultraprocessed foods typically include ingredients not commonly used in home cooking – emulsifiers, flavor enhancers, and other additives – and are often high in sugar, salt, and unhealthy fats. Examples include sugary drinks, packaged snacks, processed meats, and ready-to-eat meals.

Limitations and Considerations

It’s crucial to acknowledge the study’s limitations. The dietary assessments relied on caregiver recall, which is subject to inherent biases. The questionnaires didn’t capture detailed ingredient lists or whether foods were homemade, potentially influencing the accuracy of ultraprocessed food categorization. The study establishes a correlation, not causation. It’s possible that other factors – socioeconomic status, parenting styles, or genetic predispositions – could contribute to both dietary patterns and behavioral outcomes.

Dr. Kozeta Miliku, the principal investigator from the University of Toronto, emphasized that the findings highlight the potential relevance of early-life nutrition for multiple aspects of child development. “While the effect sizes were modest and the study is observational, the findings highlight that early-life nutrition may be relevant for multiple aspects of child development,” she told Healio. “For clinicians, this reinforces the importance of discussing overall dietary patterns in early childhood, particularly reducing reliance on ultraprocessed foods and encouraging minimally processed alternatives.”

What Might Explain the Link?

The precise mechanisms linking ultraprocessed food consumption to behavioral difficulties remain unclear. Several hypotheses are being explored. One possibility is that the high sugar and fat content in these foods can disrupt brain development and neurotransmitter function, potentially affecting mood, and behavior. Another theory suggests that the lack of essential nutrients in ultraprocessed foods may contribute to deficiencies that impact cognitive and emotional regulation. Severe weather events and related stress can also impact dietary choices and mental wellbeing, though this study did not address those factors.

Implications for Parents and Clinicians

The study’s findings don’t advocate for a restrictive or guilt-inducing approach to feeding children. Instead, they underscore the importance of prioritizing minimally processed foods – fruits, vegetables, whole grains, lean proteins – as the foundation of a healthy diet. A modeled substitution within the study suggested that replacing just 10% of energy intake from ultraprocessed foods with minimally processed alternatives could lead to modest improvements in behavioral scores.

Clinicians can play a role by discussing dietary patterns with parents during routine checkups and offering guidance on making healthier food choices. Advocating for healthier food environments in childcare settings, schools, and communities, as well as policies that support access to affordable, nutritious food, are also important steps.

Future Research Directions

Dr. Miliku and her colleagues recommend further research to delve deeper into the biological mechanisms connecting ultraprocessed foods with neurodevelopment and behavior. Longitudinal studies that track children over extended periods are needed to determine whether early dietary exposures have lasting effects on mental health. More detailed dietary assessments, including information on ingredient lists and food preparation methods, would also enhance the accuracy of future investigations.

Kozeta Miliku, MD, PhD, can be reached at [email protected].

The U.S. Embassy in Iran issued a security alert today, March 16, 2026, updating guidance for American citizens regarding potential departure options and security risks. The alert highlights concerns about potential roadside checkpoints operated by Iranian security forces and the possibility of U.S. Citizens being prevented from leaving the country or charged an “exit fee.” This situation is separate from, but concurrent with, the findings regarding ultraprocessed foods and child behavior.