The human brain develops rapidly in early life — transforming helpless infants into walking, door-opening, question-asking, willful little people. And now a new study suggests that a toddler’s diet may have some impact on his future cognitive abilities, with diets high in processed food at age 3 leading to lower IQ by age 8.
Researchers from the University of Bristol looked at data on 3,966 children born between 1991 and 1992, who were part of the Avon Longitudinal Study of Parents and Children (ALSPAC). The children’s parents had completed surveys on their kids’ diets at ages 3, 4, 7 and 8.5, and the children’s IQs were measured at age 8.5. (More on Time.com: Is School Lunch Making Your Kids Fat?)
Parents recorded their kids’ consumption of a wide variety of food and drink, including details like the fat content of milk, whether breads were refined or whole grain, and how much soda or coffee children consumed. Based on parents’ reports, researchers assigned kids to one of three diet categories: a “processed” diet, high in fat, sugar and calories; a “traditional” diet (in the British sense), made up of meat, potatoes, bread and vegetables; and a “health-conscious” diet of whole grains, fresh fruits and vegetables, rice, pasta and lean proteins like fish.
Overall, kids who ate junky fast-food diets at age 3 had a small drop in IQ at age 8.5, compared with kids eating healthy foods. The association persisted even after researchers controlled for other environmental factors that can influence IQ, such as parental education level, maternal diet in pregnancy, socioeconomic status and stressful life events.
For each unit increase in processed food diets, children lost 1.67 points in IQ. By contrast, for each unit increase in healthy diets, children gained 1.2 IQ points. Quality of diet measured at the other ages did not significantly affect IQ level by age 8, suggesting that diet may be most important during toddlers’ earliest years. (More on Time.com: More Calls to Overhaul Deceptive Front-of-Package Labeling)
The researchers found that early diet seemed to affect kids’ later verbal abilities more than their performance abilities. “Performance IQ relates to an individual’s innate intellectual ability, while verbal IQ more reﬂects the impact of education, which in turn is affected by inﬂuences such as parenting and environment,” wrote the researchers.
That’s in keeping with previous research noted by the authors:
These results are in line with previous studies we have performed in the ALSPAC cohort: overall dietary patterns in early childhood are associated with both later child behavior, in particular hyperactivity and school performance. This suggests that any cognitive/behavioral effects relating to eating habits early in childhood may well persist into later childhood, despite any subsequent changes (including improvements) to dietary intake.
It should be noted that the children included in the study already had many benefits known to foster cognitive development: they were more likely to live in homes owned by their parents, to have been breast-fed and to be from a high socioeconomic background.