Diets high in fats, sugars and processed foods are lowering toddlers' IQs, a new study has suggested.
It found eating habits among three-year-olds shape brain performance as they get older.
A predominantly processed food diet at the age of three is directly associated with a lower IQ at the age of eight and a half, according to a Bristol-based study of thousands of British children.
Food packed with vitamins and nutrients notably did the opposite, helping boost mental performance as youngsters got older, the Journal of Epidemiology and Community Health reports.
Researchers said toddlers' diets could change IQ levels later in childhood, even if eating habits improve with age.
"This suggests that any cognitive/behavioural effects relating to eating habits in early childhood may well persist into later childhood, despite any subsequent changes to dietary intake," the authors wrote.