More Cookies and Soda, More Anxiety? Ultra-Processed Foods Can Affect Children's Behavior

A study of over 2,000 children revealed that those who consumed more ultra-processed foods at age 3 showed more signs of anxiety, aggression, and behavioral difficulties at age 5. Scientists believe that small changes in diet can benefit not only the body but also the development of the child's brain.

Ultra-processed foods have already been associated with an increased risk of obesity, diabetes, and cardiovascular disease. Now, a new study suggests that their effects may go beyond physical health: they may also influence the behavior and emotional development of children even in the preschool phase.

The research indicates that a diet rich in this type of product may be related to more symptoms of anxiety, aggression, hyperactivity, and behavioral difficulties at age five.

Researchers explain that the first years of life represent an extremely important period for brain development. It is during this phase that the neural connections responsible for controlling emotions, attention, learning, and behavior are being formed.

Alterations in this process can have lasting consequences, increasing the risk of emotional difficulties and even mental disorders later in life. Although genetic factors and the family environment play an important role, diet is one of the few factors that can be modified.

So-called ultra-processed foods are industrial products formulated with various refined ingredients, additives, colorings, flavorings, emulsifiers, and preservatives. They include soft drinks, chips, filled cookies, sugary cereals, nuggets, sausages, instant noodles, processed sweets, and many ready-to-eat products. In general, they contain large amounts of sugar, saturated fat, and sodium, but offer little fiber, vitamins, and minerals important for the brain.

To investigate this relationship, scientists analyzed data from 2,077 Canadian children who participated in a large follow-up study from birth. When they were 3 years old, parents answered a detailed questionnaire about everything their children usually ate, allowing them to calculate what percentage of their daily calories came from ultra-processed foods. On average, these products represented 45.5% of all energy consumed, showing how much they already constitute a part of children's diets.

Two years later, when the children turned 5, the researchers assessed their behavior using a questionnaire widely used by psychologists and pediatricians. This instrument measures different aspects of emotional development, including symptoms called internalizing symptoms, such as anxiety, sadness, fear, and social withdrawal, and externalizing symptoms, such as aggression, impulsivity, irritability, disobedience, and hyperactivity.

The scientists also took into account many other factors that could influence the results, such as parental education, family income, maternal diet during pregnancy, breastfeeding, birth characteristics, and other aspects of childhood.

After all these adjustments, the association remained clear. The greater the consumption of ultra-processed foods at age 3, the greater the behavioral difficulties observed at age 5.

In addition, the researchers conducted a statistical simulation to estimate what would happen if some of the calories from these foods were replaced by minimally processed foods, such as fruits, vegetables, legumes, beans, eggs, meats, whole grains, and homemade preparations.

The results suggested that this change would be associated with fewer emotional and behavioral symptoms, indicating that small changes in diet can bring important benefits to child development.

It's important to highlight that this was an observational study, meaning it doesn't prove that ultra-processed foods directly cause behavioral problems. Even so, it's one of the largest studies ever conducted on the topic, and its results reinforce a growing body of evidence showing that diet quality can influence not only the body but also the developing brain.

For parents and healthcare professionals, the message is simple: encouraging a diet based primarily on natural and minimally processed foods from the earliest years of life can contribute to healthier emotional and behavioral development.

Professor Kozeta Miliku responsible for the research. Credit: University of Toronto

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Ultraprocessed Food Consumption and Behavioral Outcomes in Canadian Children

Meaghan E. Kavanagh, Zheng Hao Chen, Sukhpreet K. Tamana, Theo J. Moraes, Elinor Simons, Stuart E. Turvey, Padmaja Subbarao, Piushkumar J. Mandhane, and Kozeta Miliku

JAMA Network Open. 3 March 2026;9;(3):e260434.DOI: 10.1001/jamanetworkopen.2026.0434

Abstract: 

Ultraprocessed foods (UPF) contribute to nearly half of energy intake among preschool-aged children in Canada, yet their impact on behavioral and emotional functioning remains underexplored. To examine the associations between UPF intake at age 3 years and behavioral outcomes at age 5 years. This cohort study included children with dietary and behavioral data from September 2011 to April 2018 in the CHILD Cohort Study, a prospective Canadian pregnancy cohort. Data analysis was done between February to July 2025. UPF intake at age 3 years was assessed by a 112-item food frequency questionnaire and categorized using the NOVA system. Behavior was measured using the validated Child Behavior Checklist (CBCL; range 0-100; higher scores indicating more adverse symptoms). UPF intake measured as a continuous percentage of energy was examined using multivariable-adjusted linear regression models accounting for maternal diet, birth factors, infant feeding, and sociodemographic and early-childhood characteristics. A multivariable-adjusted substitution model estimated the association of statistically replacing 10% energy from UPF with minimally processed foods (MPF) among all children. Among 2077 participants, 1092 (52.6%) were male; 1376 children (66.2%) were White, 480 children (23.1%) were multiracial, and 221 children (10.7%) were identified as another ethnic group. At age 3 years, UPF contributed a mean (SD) of 45.5% (11.6%) of total energy intake. At age 5 years, the mean (SD) CBCL scores were 44.6 (9.1) for internalizing, 39.6 (9.4) for externalizing, and 41.2 (9.0) for total behavior. Each 10% increase in energy from UPF was associated with higher CBCL internalizing (β = 0.81 [95% CI, 0.43 to 1.19]), externalizing (β = 0.47 [95% CI, 0.08 to 0.87]), and total (β = 0.64 [95% CI, 0.27 to 1.01]) scores. Substitution of 10% energy from UPF with MPF was associated with lower internalizing (β = –0.91 [95% CI, –1.33 to –0.49]), externalizing (β = –0.49 [95% CI, –0.93 to –0.06]), and total (β = –0.70 [95% CI, –1.12 to –0.29]) scores. In this cohort study of preschoolers in Canada, higher UPF intake was associated with adverse behavioral and emotional symptoms by age 5 years. These findings suggest that replacing UPF with MPF during the preschool years may support healthier behavioral development, with potential benefits for long-term mental health. These findings also support ongoing policy actions that promote MPF and underscore the need for early-life dietary interventions.