Ultra-Processed Foods May Lower Children’s IQ, Study Finds

Key points

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

Ultra-processed foods have attracted considerable attention because of their potential harmful effects on adults’ health. Research has associated eating too much of them with conditions ranging from diabetes and cancer to depression. Yet much of that research has centred on adults. A new study from the University of Illinois indicates that ultra-processed foods could also be harmful for the youngest people in the global population.

In January, University of Illinois researchers published findings from their study in the British Journal of Nutrition. They analysed the 2015 Pelotas Birth Cohort to explore the relationship between children’s eating patterns and their cognitive performance. In a statement, the researchers said the results “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 what the children ate at age two, the team evaluated their cognitive performance when they reached the first years of school, between six and seven years old.

Ultra-processed foods and children’s IQ scores

Rather than examining particular foods or nutrients, the team assessed “overall” dietary patterns, dividing them into two categories. The “healthy” pattern featured beans, fruit, vegetables, baby foods and natural fruit juices. The “unhealthy” pattern included snacks, instant noodles, sweet biscuits, sweets, fizzy drinks, sausages and processed meats. Children whose diets more closely matched the “unhealthy” pattern at two years old received lower scores in IQ tests at six to seven years old.

Crucially, the link remained after accounting for a broad range of social, economic and family influences 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,” said 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 study authors further found that the results were “especially concerning” for children considered biologically vulnerable already. This classification referred to children with “early-life deficits” in weight, height or head circumference. They said this forms 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.”

Smart swaps to reduce ultra-processed foods

There is no need to overhaul a child’s diet in one go. Straightforward, small substitutions can meaningfully lower their intake of ultra-processed foods while keeping meals convenient and appealing to children. The study considered overall dietary habits rather than the occasional treat. What matters most is concentrating on foods children regularly eat at meals, rather than trying to achieve perfection every time.

• 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 purée, 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 sliced 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

Why the healthy pattern was not linked to higher IQ

Although children who followed “unhealthy” dietary patterns had lower IQ scores, the study did not establish that the healthy pattern resulted in higher IQ scores. Flores explained that this was probably because fruit and vegetables in the healthy pattern were 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 result occurs, so it cannot say precisely what causes it. However, Flores pointed to findings in other research, which suggest 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.”

Would Flores expect the same pattern to be found in other countries? “Considering the worldwide dissemination and higher prevalence of ultraprocessed foods, I think so,” she said.

Reviewed by

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