The food a two-year-old eats may have a surprisingly long-lasting impact, extending well into their school years and potentially influencing their cognitive development. A recent longitudinal study, following thousands of children in Brazil, has found a significant link between diets high in ultraprocessed foods at age two and lower IQ scores at ages six and seven.
Researchers at the University of Illinois and the Federal University of Pelotas analyzed data from the 2015 Pelotas Birth Cohort, a comprehensive study tracking children from birth. The findings, published in the British Journal of Nutrition, add to a growing body of evidence highlighting the critical role of early childhood nutrition in shaping brain development. The study emphasizes that it’s not necessarily about the absence of healthy foods, but rather the consistent presence of unhealthy ones.
The research team identified two dominant dietary patterns among the toddlers: a “healthy” pattern rich in beans, fruits, and vegetables, and an “unhealthy” pattern characterized by snacks, instant noodles, sugary drinks, and processed meats. While the vast majority – 92% – of children in the cohort consumed the “healthy” pattern, it was the adherence to the “unhealthy” pattern that consistently correlated with lower IQ scores. This suggests that, in this population, a baseline level of healthy eating was already common, making it difficult to demonstrate a boost from even more fruits and vegetables. The key differentiator was the consumption of ultraprocessed foods.
“The unhealthy dietary pattern was negatively associated with IQ,” explained Thayna Flores, an assistant professor in the Department of Health and Kinesiology at the University of Illinois and one of the study’s authors. The association remained statistically significant even after accounting for a wide range of socioeconomic factors, including maternal education and household income, as well as other potential confounding variables like breastfeeding duration and early childhood stimulation.
Interestingly, the study revealed a “cumulative disadvantage” effect. The negative impact of a poor diet was most pronounced in children who already faced early-life vulnerabilities, such as low birth weight, stunted growth, or a smaller head circumference. These children appeared to be particularly susceptible to the detrimental effects of ultraprocessed foods on cognitive development.
Researchers hypothesize that ultraprocessed foods may interfere with brain development through several biological mechanisms. These include systemic inflammation, oxidative stress, and disruptions to the gut-brain axis – the complex communication network between the digestive system and the brain. While the study didn’t directly investigate these mechanisms, existing research supports these potential pathways.
The study’s design focused on overall dietary patterns rather than individual nutrients or foods. Using a statistical method called principal component analysis, researchers were able to identify these common combinations of foods consumed by the toddlers. This approach provides a more holistic view of dietary intake than focusing on isolated food items.
The findings from this Brazilian cohort may have broader implications, given the increasing prevalence of ultraprocessed foods in diets worldwide, including in high-income countries. While direct comparisons should be made cautiously, Flores believes the results are informative and can generate hypotheses for studies conducted elsewhere.
“Although the study is based in southern Brazil, its implications may extend far beyond Pelotas,” Flores stated. “Ultraprocessed foods are now common in early childhood diets worldwide, including in high-income countries.”
The researchers acknowledge that the study doesn’t prove a causal relationship between ultraprocessed food consumption and lower IQ scores. However, the longitudinal design, large sample size, and careful control for confounding factors strengthen the evidence. Further research is needed to confirm these findings and to explore the underlying biological mechanisms.
For policymakers, the study underscores the importance of strengthening nutritional counseling during routine child health visits. Emphasis should be placed on limiting the habitual offering of ultraprocessed and unhealthy foods to young children. While guidelines already exist, the study suggests a gap between recommendations and actual dietary practices.
“Our results reinforce the importance of strengthening counseling during routine child health visits, emphasizing the need to limit the habitual offer of ultraprocessed and unhealthy foods,” Flores said. “Despite established guidelines, consumption of ultraprocessed foods is already common at this age.”
Key Questions Answered:
A: No. The study looked at habitual dietary patterns. It’s the consistent, daily reliance on ultraprocessed foods like instant noodles and soft drinks at age two that was linked to lower cognitive scores years later.
A: In this specific study, nearly all children were eating healthy foods (like beans and fruit). Because there wasn’t much variety—almost everyone had a healthy baseline—the researchers couldn’t statistically “see” a boost. The real difference was made by the addition of unhealthy foods.
A: While the brain is plastic, the study suggests that age two is a critical window. Children who start with a disadvantage (like being small at birth) are the most vulnerable to the negative effects of a poor early diet, making early intervention vital.
