We can not randomize breastfeeding, although it is possible to randomize breast milk: Lucas et al23 conducted an ingenious study in which premature infants who were
fed their mother's milk from a bottle did better on follow - up
testing than children who were
fed formula.
Most previous studies have compared breast
fed children with children who were exclusively
formula fed, but some studies have found that the correlation between breast
feeding and cognitive ability increases with a longer duration of breast
feeding.3 13 30 A Finnish study of 1163 children found a mean difference of 2.4 points on a cognitive
test at 6 months of age between children breast
fed for less
than five months, compared to children breast
fed for at least five months.10
In 2007, researchers reported in the journal Early Human Development that children who had received no DHA in
formula or breast milk during the first 17 weeks of life had poorer visual acuity at age 4, and did worse on language
tests showing verbal IQ,
than those who
fed breast milk.