What a child eats at just two years old may already be shaping how their brain develops for years to come. A new study has found that toddlers who consumed higher amounts of ultra-processed foods scored lower on intelligence tests when assessed at six and seven years of age. The findings add to a growing body of evidence suggesting that early nutrition plays a far more significant role in cognitive development than many parents might realize. This research offers a sobering look at what ends up on the plates of the youngest and most vulnerable members of our society.
The study draws on data from the Pelotas Birth Cohort, a long-running project that has been tracking thousands of children born in southern Brazil from birth into adulthood. In this particular analysis, scientists from the University of Illinois and the Federal University of Pelotas gathered detailed dietary information on children at two years old and then evaluated their cognitive abilities when they reached school age. Rather than examining individual foods in isolation, the research team focused on broader eating patterns to understand which overall diets were associated with better or worse outcomes. This approach gave a much more complete picture of how daily food choices shape a young child’s intellectual trajectory.
Two dominant dietary patterns emerged from the data. The first, described as “healthy,” included foods like beans, fruit, vegetables, porridge, and fruit juices. The second pattern, labeled “unhealthy,” was dominated by snacks, instant noodles, sweet cookies, candy, carbonated drinks, sausages, and other processed meats. Children whose diets at age two leaned more heavily toward the unhealthy pattern were the ones who showed lower IQ scores several years later. The contrast between the two patterns made the association between diet and cognitive development particularly clear.
What makes the findings especially compelling is that the link between ultra-processed food consumption and lower IQ persisted even after researchers accounted for a wide range of other factors. These included the mother’s level of education, the family’s socioeconomic status, how long the child was breastfed, and the degree of intellectual stimulation provided at home. Professor Thayna Flores, one of the study’s authors, noted that while parental IQ was not directly measured, the team used proxy indicators of the home environment, such as whether families encouraged learning and whether children attended kindergarten. The fact that the association survived these controls makes the result harder to dismiss.
Interestingly, the healthy dietary pattern did not show a corresponding link to higher IQ scores. Flores explained that this is likely because nutritious food was already so common among the children in the study that statistical differences were difficult to detect. As she pointed out, “about 92 percent of children regularly ate four or more foods that characterize the healthy pattern,” meaning there simply was not enough variation in healthy eating habits to generate a clear signal. The real differentiator, it seems, was the degree to which ultra-processed foods dominated a child’s diet.
The negative effects were most pronounced among children who were already considered more vulnerable, particularly those who had lagged behind in weight, height, or head circumference during infancy. This suggests that poor dietary quality can compound existing developmental challenges rather than acting as a standalone risk factor. Although the study did not directly investigate the biological reasons behind these results, earlier research offers some possible explanations. Diets heavy in ultra-processed foods may interfere with brain development through inflammatory processes, oxidative stress, and disruptions to the gut-brain axis.
The study was conducted in Brazil, but Flores and her colleagues stressed that the implications reach well beyond any single country, since ultra-processed foods are now a global phenomenon found in virtually every market and household. The message from the researchers is unambiguous: “We need to consider the rise of ultra-processed food. Stronger actions now can help reduce its consumption, especially in early childhood.” Policymakers, healthcare providers, and parents alike are being called on to take this issue seriously before a generation of children pays the cognitive price.
Ultra-processed foods are defined under the NOVA classification system, developed by researchers at the University of São Paulo, which categorizes foods based on the extent and purpose of their processing rather than their nutritional content alone. These products typically contain ingredients rarely found in home kitchens, such as hydrogenated oils, artificial flavors, emulsifiers, and preservatives, and they are engineered specifically for palatability and long shelf life. Studies across multiple countries have linked high ultra-processed food consumption in both children and adults to a range of health issues, including obesity, type 2 diabetes, cardiovascular disease, and depression. The gut-brain axis, which is emerging as a critical area of research, refers to the bidirectional communication network between the gastrointestinal tract and the central nervous system, and disruptions to it through poor diet are increasingly believed to have wide-ranging neurological consequences. Early childhood, particularly the first three years of life, is widely recognized by neuroscientists as a period of extraordinary brain growth and plasticity, making the quality of nutrition during this window especially consequential for long-term outcomes.
If this research has you thinking twice about what goes into a toddler’s lunchbox, share your thoughts and experiences in the comments.
