Ultraprocessed foods, like some fast foods, frozen foods, baked goods and lunch meats, contain refined ingredients such as sweeteners, flavorings and preservatives, but few, if any, whole ingredients and nutrients. These foods are designed to look good and are usually high in sugar and sodium, so they taste good and people start to crave them.

These foods make up more than half of the calories consumed by children in the U.S. between the ages of one and five years old. The trouble is that early childhood is an important window for brain development, making this exposure to ultraprocessed foods a serious concern.

Few studies had looked at the effects of ultraprocessed foods on brain development in young children until a team led by researchers at the Children's Hospital of Los Angeles decided to see how they affected brain volume in children six and under.

Kids with a ten percent higher consumption of ultraprocessed foods had an almost two percent decrease in the volume of subcortical regions of the brain.

The researchers followed 144 Latino/Hispanic mother-child pairs. When they measured the children's brain volume at age six using magnetic resonance imaging (MRI) scans, they found that those kids with a ten percent higher consumption of ultraprocessed foods had an almost two percent decrease in the volume of subcortical regions of the brain, which include the accumbens, amygdala, pallium, putamen and thalamus.

“What children eat early in life may shape brain development in ways that we are just beginning to understand,” Michael Goran, senior author on the study, told TheDoctor.

These regions of the brain are where reward processing, emotion and motivation take place. For example, a recent Canadian study found that preschool-age kids who ate a diet high in ultraprocessed foods were more likely to have emotional and behavioral problems a few years later.

When the children in the current study were two years old they were given tests of motor and language skills to measure their cognitive function and to see if the decrease in volume also had an effect on cognitive function. And when the children were six years old, the team used computerized tests of memory, attention and their ability to understand new information to measure cognitive function.

Early childhood is a key time for brain development; it is also when lifelong eating habits are established.

The researchers reported that ultraprocessed foods had no effect on cognitive function, however, as Goran, director of the nutrition and obesity program at The Saban Research Institute at the Children's Hospital of Los Angeles, explained, “Even without changes in cognitive performance, we are seeing measurable differences in brain structure.”

The timeframe is important. Early childhood is a key time for brain development; it is also when lifelong eating habits are established. Goran suggests parents offer kids whole foods such as fresh fruits and vegetables and avoid ready-to-eat meals, frozen dinners and sweets. Parents can also give kids diluted fruit juice or water and skip sugar-sweetened beverages like sports drinks and sodas.

The study is published in The American Journal of Clinical Nutrition.