Ultra-Processed Foods May Be Linked to Lower IQ Scores in Children, Study Finds

Key points

• A new study has found that toddlers who ate more ultra-processed foods - including instant noodles and sweet biscuits - recorded lower IQ scores at six to seven years old.
• The results indicate that diets rich in ultra-processed foods could adversely affect brain development, even when socioeconomic and family influences are taken into account.
• Researchers said the association was strongest in children who were already biologically vulnerable because of early growth deficits.

Ultra-processed foods have attracted extensive attention for their possible harmful effects on adults’ health. Research has associated excessive consumption with conditions ranging from diabetes and cancer to depression. Yet much of that research has centred on adults. New research from the University of Illinois indicates that ultra-processed foods may also be harmful for the youngest people in the global population.

Ultra-processed foods and children’s IQ

In January, University of Illinois researchers published findings from their study in the British Journal of Nutrition. They examined the 2015 Pelotas Birth Cohort to explore how children’s eating patterns affect cognitive performance. In a statement, the researchers said the findings "add to growing global evidence that early childhood nutrition - particularly exposure to ultraprocessed foods - may play a meaningful role in shaping brain development."

The researchers described the Pelotas Birth Cohort as one of Latin America’s most "comprehensive long-running population studies". It tracked thousands of children from birth. Using detailed records of the foods children ate at age two, the team assessed their cognitive performance when they reached early school age, between six and seven years old.

Rather than assessing individual foods or nutrients, the team considered "overall" dietary patterns, dividing them into two categories. The "healthy" pattern included beans, fruit, vegetables, baby foods and natural fruit juices. The "unhealthy" pattern included snacks, instant noodles, sweet biscuits, sweets, soft drinks, sausages and processed meats. Children whose diets aligned more closely with the "unhealthy" pattern at age two achieved lower IQ test scores at ages six to seven.

The study’s findings and biological vulnerability

Crucially, the relationship remained after accounting for numerous social, economic and family circumstances that can also affect cognitive development. "The analyses were adjusted for child's sex, maternal age, maternal schooling, maternal work, maternal depression, family structure, parental relationship, socioeconomic status, number of people in the household, number of older siblings, preschool, score of stimulation, duration of exclusive breastfeeding, and food introduction before six months," explained Thayna Flores, an assistant professor in the Department of Health and Kinesiology in the College of Applied Health Sciences at the University of Illinois and one of the study’s authors.

The authors also said the findings were "especially concerning" for children considered biologically vulnerable - those with "early-life deficits" in weight, height or head circumference. They described this as part of a "cumulative disadvantage."

"According to the literature, children with a deficit in height and head circumference from birth to the first year of life were more likely to be classified as having a low IQ," Flores said. "Other studies suggest that insufficient growth before age two is related to impaired cognitive development."

Simple swaps to reduce ultra-processed foods

There is no need to overhaul a child’s diet immediately. Practical, gradual substitutions can meaningfully reduce ultra-processed foods while keeping meals straightforward and appealing to children. The study considered overall dietary habits rather than occasional treats. What matters most is focusing on the foods children regularly have at mealtimes, instead of trying to make every meal perfect.

• Instead of: Sugary breakfast cereal
  Try: Porridge topped with nut butter and fruit, or plain yoghurt with granola and berries
• Instead of: Packaged fruit snacks
  Try: Fresh fruit, unsweetened apple sauce or pieces of frozen fruit
• Instead of: Instant noodles
  Try: Wholegrain pasta with olive oil and Parmesan, or rice with scrambled egg and vegetables
• Instead of: Processed deli meats
  Try: Shredded roast chicken, mashed beans, hummus or nut butter sandwiches
• Instead of: Sweetened drinks or fizzy drinks
  Try: Water with sliced fruit, milk or diluted 100% fruit juice

Although the study found lower IQ scores among children who followed “unhealthy” dietary patterns, it did not establish that the healthy pattern caused higher IQ scores. Flores said this was likely because fruit and vegetables within the healthy pattern are already common in children’s diets. “The lack of association observed for the healthy dietary pattern can be largely explained by its lower variability,” she said. “Approximately 92% of children habitually consumed four or more of the foods that characterize the healthy pattern.”

The team did not test why the lower IQ outcome occurs, so the reason remains unclear. However, Flores referred to other published research showing that "Diets of poor nutritional quality, particularly those high in ultraprocessed foods, may interfere with neurodevelopmental processes through mechanisms involving systemic inflammation, oxidative stress and alterations in the gut–brain axis."

Asked whether she thought the pattern would also apply in other countries, Flores said, "Considering the worldwide dissemination and higher prevalence of ultraprocessed foods, I think so."

Reviewed by

Lauren Manaker MS, RDN, LD, CLEC: Lauren is an award-winning registered dietitian and three-time book author, with more than 22 years in the field.