A study of 185 individuals followed-up from birth to the age of 19 years showed that those with chronic iron deficiency in infancy had lower cognitive scores than those without the deficiency.
This difference was seen up to the age of 19, and in children from low socioeconomic backgrounds the cognitive gap widened more than twofold with age.
A second study from Canada showed that infants bottle-fed until the age of three were 2.5 times more likely to be iron deficient than those who had been weaned.
This could be because excessive milk consumption impairs iron absorption from the gut or is associated with a reduced intake of iron-rich food or drink.