Ultraprocessed foods and children's brains: what the data show

What is the link between ultraprocessed foods and children's brains?

The link between ultraprocessed foods and children's brains goes beyond obvious junk food: the study behind it found the association across every type of ultraprocessed product, including the breakfast cereal a family treats as a safe choice. Researchers at Children's Hospital Los Angeles followed children from infancy to age 6 and published their findings in 2026.

Ultraprocessed foods are products built mainly from refined ingredients, sugar, fats and additives, with little whole food left inside them. The category covers ready meals, sweetened cereals, salty snacks and sugary drinks, and it also covers many foods that look wholesome, such as sandwich bread or supermarket oat cookies.

STUDY Children with higher cumulative ultraprocessed food intake from infancy carried smaller volume in deep brain regions at age 6, with no matching difference in cognitive testing. Ottino-González et al., 2026, American Journal of Clinical Nutrition.

Important: the study shows a statistical association between high ultraprocessed intake and smaller volume in specific brain regions, the kind of population-level pattern that motivates deeper mechanistic research.

How was the study that followed children from 6 months to 6 years designed?

The study followed 144 Latino and Hispanic families in Southern California, from birth through age 6. Researchers logged diet with repeated 24-hour recalls at 6, 12, 24 and 72 months, to calculate the share of calories coming from ultraprocessed foods at each stage.

Children completed cognitive testing at ages 2 and 6, and at age 6 they also had a brain MRI, with volume measured across 16 subcortical regions. This pairing, years of dietary data alongside brain imaging, is rare at such young ages.

How much does ultraprocessed food intake climb as a child grows?

The climb is steep. Across the full sample, the share of calories from ultraprocessed foods rose from 16.4% at 6 months to 55.5% at 6 years, meaning more than half of a child's plate eventually came from this single food category.

The steepest jump, 21.2 percentage points, landed between 24 and 72 months, exactly when a child moves into more regular, family-style meals. This window between ages 2 and 6 looks like the critical stretch for the eating habits a child carries forward.

How much ultraprocessed food do American children eat today?

A lot. Nationally representative NHANES data show that ultraprocessed foods supplied 67% of the total daily energy US children and teenagers consumed in the most recent cycle analyzed, meaning close to two out of every three calories a child eats now come from this single category, a scale that keeps the conversation about ultraprocessed foods and children's brains directly relevant to American families.

That share climbed steadily over two decades, from 61.4% in 1999-2000 to 67.0% in 2017-2018, and the rise landed hardest among non-Hispanic Black youths (62.2% to 72.5%) and Mexican American youths (55.8% to 63.5%), compared with non-Hispanic White youths (63.4% to 68.6%).

STUDY Among 33,795 US youths aged 2-19 years tracked across ten NHANES cycles, the estimated share of total energy from ultraprocessed foods climbed from 61.4% to 67.0% between 1999 and 2018. Wang et al., 2021, JAMA.

A companion national analysis links that climb directly to diet quality. Children in the group with the lowest ultraprocessed intake had a 31.3% rate of poor diet quality, while children in the group with the highest intake, above 79% of energy from ultraprocessed foods, reached a 71.6% rate.

STUDY Among US children, the estimated proportion with poor diet quality rose from 31.3% in the lowest quintile of ultraprocessed intake to 71.6% in the highest quintile. Liu et al., 2022, American Journal of Preventive Medicine.

Which food categories add the most ultraprocessed calories to an American child's plate?

Four categories. Ready-to-heat and ready-to-eat meals, sweet snacks and bakery sweets, sugar-sweetened drinks, and processed fats, oils, condiments and sauces together supply about half of all the ultraprocessed calories American children eat, according to the same nationwide NHANES analysis.

Ready-to-heat and ready-to-eat meals climbed the fastest of any subgroup, from 2.2% to 11.2% of total energy between 1999 and 2018, and sweet snacks and sweets, a group that includes cakes, cookies, pies and pastries, grew from 10.7% to 12.9%. Sugar-sweetened drinks moved the other way, falling from 10.8% to 5.3% of total energy over the same two decades, and processed fats, oils, condiments and sauces slid from 7.1% to 4.0%.

Ready-to-heat meals and sweet bakery items now carry more weight in an American child's ultraprocessed intake than sugary drinks do, a reversal from the soda-heavy pattern many people still picture when they hear the term.

Ready-to-heat meals

Frozen pizza, takeout-style bowls and similar ready meals, now 16.7% of ultraprocessed calories. Typically high in sodium, saturated fat and emulsifiers.

Sweet snacks and sweets

Cookies, cakes, pastries and candy, 19.3% of ultraprocessed calories, the single largest subgroup in the American child's diet.

Sugar-sweetened drinks

Soda, sweetened fruit drinks and sports drinks, 7.9% of ultraprocessed calories, down sharply since 1999 but still a measurable slice.

Fats, oils, condiments and sauces

Bottled dressings, mayonnaise and similar condiments, 6.0% of ultraprocessed calories, the smallest of the four named subgroups.

Which brain regions were smaller in children with high intake?

Eight regions, all deep inside the brain. Researchers identified statistically smaller volume, after correction for multiple comparisons, in the accumbens, amygdala, pallidum, putamen and thalamus, bilaterally in several of these structures.

These regions are far from random: they govern reward, emotion, movement and the relay of sensory signals, a large share of how a child feels pleasure, manages mood and stays focused.

How much smaller was brain volume in the highest-intake children?

Considerably smaller. Children in the highest consumption quartile, with 62% or more of calories from ultraprocessed foods, carried up to 8.3% smaller volume on average in specific regions compared with children in the lowest quartile, at 31% or less.

The relationship tracked with dose: each additional 10% of ultraprocessed foods in the diet lined up with roughly 1.9% smaller volume, and that trend held steady across the full range of consumption.

How can a sweet or salty snack affect the brain's reward circuit?

Through dopamine. Very sweet or fatty foods strongly activate the brain's reward circuit in humans, releasing dopamine in the striatum every time they are eaten.

In animal studies, repeated exposure to these foods reduced striatal D2 dopamine receptors. In practical terms, the reward circuit grows less sensitive over time and calls for a stronger stimulus to reach the same satisfaction.

What's really inside a box of sweetened breakfast cereal?

More than sugar. A typical box of sweetened breakfast cereal, among the most common ultraprocessed products on the American breakfast table, usually contains added sugar, emulsifiers, and sometimes artificial sweeteners and food dyes. Each ingredient carries a different level of evidence for its possible effect on the brain.

Added sugar carries the strongest documented footprint, backed by data from humans and animals alike. Emulsifiers and artificial sweeteners are backed mainly by in vitro data, meaning cell-culture studies, well ahead of large clinical trials in children.

What do these brain regions control, and what does other research show?

A great deal, and none of it by accident. The accumbens sits at the center of the reward circuit, activated by pleasurable cues such as food. The amygdala processes emotion and emotional memory, important for mood regulation. The pallidum and putamen participate in movement, motivation and reward-based learning, while the thalamus works as the central relay station carrying information toward the cortex.

STUDY A systematic review of 35 studies covering more than 84,000 children and adolescents linked higher ultraprocessed intake with weaker attention and executive function. Nguyen et al., 2025, Food Frontiers.

Why did cognitive test scores stay similar even as brain structure changed?

Structural change likely comes first, ahead of any functional change. Even though eight regions showed smaller volume, cognitive testing at ages 2 and 6 showed comparable performance across children with high and low intake.

Researchers read this as an early stage, where structure shifts first, while function may show an effect later, or at a larger scale of exposure. A child can perform at a typical level today, while the brain already carries measurable structural change.

1. 1

   Today: structural change

   Smaller volume across eight subcortical regions, measurable on MRI at age 6.

2. 2

   Later: a possible functional effect

   Long-term studies can show whether, when and to what degree this structural difference translates into behavior or cognition over time.

What can you change in your child's breakfast and snacks?

Three steady changes to the everyday breakfast and snack routine carry more practical weight than a strict, short-lived diet.

Start with the meal that repeats every single day, breakfast, since that is where a change carries the largest cumulative effect on total ultraprocessed exposure over time. A related question worth asking is which everyday foods actually support the gut microbiome, since breakfast is where that swap is easiest to make.

• Swap sweetened breakfast cereal for oatmeal or bulgur with fresh fruit
• Trade deli-meat toast for whole-grain bread with egg or cheese
• Trade a packaged cereal bar for fruit with a handful of nuts

Many of these swaps line up naturally with a Mediterranean-style eating pattern, which makes them easier to sustain past the first week.