Think about what every parent knows deep down: the things your toddler puts in their mouth today don’t just fuel their afternoon. They’re building something. Bones. Immune systems. A brain that will eventually try to read, argue with you about bedtime, and one day do algebra homework. The connection between early food and long-term health isn’t new, but what researchers are starting to map out is how specific, much it matters, and how early the clock actually starts.
A growing body of work is looking closely at one particular category of food: ultraprocessed products. These aren’t just “junk food” in the casual sense. Ultraprocessed foods are industrial formulations, products made primarily from refined substances extracted from whole foods, with long lists of additives, preservatives, and flavor enhancers that don’t exist in a home kitchen. Think instant noodles, packaged snacks, sausages, soft drinks, and sweet biscuits. The kind of thing that’s easy, cheap, and engineered to be hard to stop eating. Also, the kind of thing a lot of toddlers eat regularly.
New research is now asking a sharper question than just “is this bad for kids?” The question is: does eating ultraprocessed food lower a child’s IQ? And the data from one of the most rigorous long-term child health studies in the world is starting to answer it.
What the Pelotas Birth Cohort Study Found About Children’s Diets
The specific research comes from the 2015 Pelotas Birth Cohort, a long-running study tracking children born in southern Brazil from birth through childhood and beyond, analyzing how early-life diet, environment, and biology shape development over time. Published in 2025 and authored by researchers including Glaucia Treichel Heller and Thaynã Ramos Flores, the British Journal of Nutrition study is one of the most detailed examinations to date of the link between ultraprocessed food at age two and child IQ scores.
The peer-reviewed study, which analyzed more than 3,400 children, collected detailed information on what each child was eating at two years old, then assessed their cognitive performance, through standardized IQ testing, when they reached ages six and seven. Researchers used a method called principal component analysis to group children’s eating habits into patterns rather than tracking individual foods. This approach lets scientists see the full picture: not whether a child occasionally ate a cracker, but what their overall diet actually looked like day to day.
Two main dietary patterns emerged. One was built around beans, fruits, vegetables, and other whole foods. The other was characterized by instant noodles, sausages, soft drinks, packaged snacks, and sweets, the hallmarks of an ultraprocessed diet. Then the researchers waited, and watched, and measured.
How Diet at Age Two Affects Brain Development by Age Seven
The results were clear. Children whose diets more closely matched the unhealthy, ultraprocessed pattern at age two had lower IQ scores at ages six and seven. Crucially, this association held up even after adjusting for maternal education, socioeconomic status, breastfeeding duration, early childhood education, and home stimulation, all the factors that typically explain differences in children’s cognitive performance.
In other words, the diet-IQ link wasn’t just a proxy for poverty or a less stimulating home environment. It showed up independent of those things.
The scale of the difference matters. Children with high adherence to the ultraprocessed dietary pattern showed an average IQ drop of approximately two points by age seven. For children already facing early-life developmental deficits, things like low weight, height, or head circumference for their age, the reduction was nearly five IQ points. That’s a meaningful gap. In practical terms, a five-point difference in IQ can affect how a child processes information in a classroom, how quickly they learn to read, and how well they manage complex tasks.
One finding surprised even the researchers. The healthy dietary pattern, the one built around fruits, vegetables, and beans, was not associated with higher IQ scores. The authors attributed this to the fact that the healthy foods were so widespread in the study population that there wasn’t enough variation to detect an effect. Approximately 92 percent of children regularly consumed four or more of the foods that defined the healthy pattern.
This doesn’t mean good food doesn’t matter, it almost certainly does. What it tells us is that in a population where kids are already eating reasonably well, the thing that separates higher from lower cognitive outcomes is the presence of ultraprocessed foods, not simply the absence of vegetables.
It’s also worth noting how the study measured ultraprocessed food consumption. Researchers relied on the NOVA classification system, a widely used framework developed by Brazilian epidemiologist Carlos Monteiro that categorizes foods not by nutrient content but by the degree and purpose of their industrial processing. Under NOVA, it’s not the sugar or the fat in a food that flags it as ultraprocessed , it’s the combination of industrial ingredients, additives, and manufacturing processes that have no equivalent in home cooking. This distinction matters because it shifts the focus away from individual nutrients and toward the overall quality and character of the food itself, which is exactly the lens researchers used when looking at these children’s diets.
Why Ultraprocessed Foods May Disrupt a Child’s Developing Brain
The study didn’t directly test biological mechanisms, but the science pointing to why this happens is building in parallel. The short version is that a toddler’s brain isn’t just growing, it’s wiring itself. Neurons are forming connections at a rate that won’t happen again for the rest of that child’s life. The raw materials for that process come from food.
A 2025 review published in Frontiers in Public Health by researchers at ETH Zurich found that ultraprocessed foods may cause lasting deficits in early-life cognitive development and increased susceptibility to mental health disorders. The review also reported that longitudinal data from the Raine Study link high-UPF diets to a 5 percent reduction in hippocampal volume after adjustment for vascular risk factors. The hippocampus is the part of the brain most associated with memory and learning, exactly the functions a young child needs to develop well before they start school.
The same review cited two complementary datasets, a 2025 Framingham analysis and a 2024 meta-analysis of nine cohorts, showing a 25 to 35 percent excess risk of all-cause dementia in adults with the highest ultraprocessed food consumption, with evidence pointing to gut dysbiosis, systemic inflammation, and insulin resistance as the biological pathways disrupting brain structure. While that research focuses on adults, the mechanisms are the same ones now being proposed for children. A diet that drives inflammation and disrupts the gut-brain connection doesn’t suddenly become harmless just because the person eating it is two years old.
Think of it this way: the gut and the brain are in constant conversation. They’re connected by a communication highway called the gut-brain axis. When a child’s gut microbiome, the community of bacteria that helps regulate digestion, immunity, and even mood, is disrupted by a diet high in additives and low in fiber, that conversation gets noisy. The signals that support healthy brain development don’t get through clearly.
There’s also the question of what ultraprocessed foods displace. When a toddler fills up on low-fiber, additive-laden snacks, they’re not eating the foods that actually supply the building blocks of brain development: iron for oxygen transport to developing neural tissue, zinc for neuronal signaling, long-chain omega-3 fatty acids for myelin formation, and choline for memory and attention circuits. These aren’t optional extras. They’re structural requirements during a period when the brain is growing faster than it ever will again. A diet that crowds out nutrient-dense food isn’t just adding harmful inputs , it’s removing essential ones at the worst possible time.
If you’re thinking about your child’s diet and wellbeing, this is exactly the kind of research that reframes the conversation from “treats are fine in moderation” to “what’s the actual baseline we’re working from?”
This Isn’t Just a Brazil Story
It would be tempting to read a study set in southern Brazil and assume it doesn’t apply to kids in the US. It does. US toddler ultraprocessed food data shows that toddlers in the US obtain 47 percent of their daily calories from ultraprocessed foods, with school-aged children getting 59.4 percent of their daily calories from the same sources. Nearly half of what America’s youngest children eat, before they can even fully hold a fork, is already ultraprocessed.
Research also shows that high-UPF diets in children are associated with increased rates of anxiety, depression, and ADHD. Cognitive performance doesn’t exist in isolation. A child whose attention regulation and emotional processing are also affected by diet is facing compounding disadvantages at school, long before anyone thinks to connect those struggles back to what was in their lunchbox at age two.
The Pelotas Birth Cohort study is observational, meaning it identifies associations rather than proving direct cause and effect. That’s a real limitation worth stating clearly. But the consistency of the finding across different socioeconomic groups, after controlling for a wide range of confounding variables, makes it hard to dismiss.
What to Do Now
The first thing to hold onto is that this isn’t about being a perfect parent or eliminating every cracker from your home. It’s about understanding that the toddler years are a particularly sensitive window, and that the dietary patterns you establish now can echo forward in ways that aren’t immediately visible.
Practically speaking, the ultraprocessed foods identified in the research aren’t obscure. Instant noodles, packaged sausage products, soft drinks, and sweet biscuits are all common toddler foods precisely because they’re convenient and kids tend to eat them without complaint. The issue isn’t an occasional serving, it’s when these foods form the majority of a young child’s diet, consistently, across months and years.
Researchers note that early-life exposure to ultraprocessed foods may contribute to lasting cognitive deficits and an increased vulnerability to mental health disorders, emphasizing the need for targeted dietary approaches in young children. That emphasis on early childhood is meaningful, and it suggests this is a window worth protecting while it’s still open.
You don’t have to overhaul everything at once. Start with the most frequent offenders. Swap the soft drink for water or plain milk. Replace packaged sausage snacks with boiled eggs or cheese. Look at what your child is eating most often across a typical week, not just what they had today. The goal isn’t restriction, it’s building a baseline where whole foods are the default and ultraprocessed options are genuinely occasional, not structural.
The Pelotas study tracked children who were already two. But the evidence on early childhood nutrition and brain development strongly suggests that earlier is always better. Early childhood is a critical window for cognitive development, during which diet can meaningfully influence long-term brain function and learning outcomes. The habits formed during the toddler years don’t just affect how kids eat at five or ten, they shape the cognitive scaffolding those children will spend the rest of their lives building on.
That’s not a reason for panic. It’s a reason to pay attention.
A.I. Disclaimer: This article was created with AI assistance and edited by a human for accuracy and clarity.