Researchers from the University of Pelotas in Brazil analysed data from over 3000 people born in Brazil in 1982. They found that people who had been breast fed as a baby had higher IQ, longer schooling and higher earnings as adults than people who were not breast fed. The longer they were breast fed, the greater the benefits.
Previous studies have been criticised for not separating the effects of breast feeding from socio-economic status. If breast feeding is more common in people who are well-educated or with better access to healthcare then it is hard to know whether the benefits of being a breast-fed baby come from breast feeding itself or from the confounding factors of being the child of better-educated, more well-off parents.
What’s different about this study is that, in their sample of the Brazilian population, breast feeding was not more common in particular socio-economic groups. The rates of breast feeding were spread across groups that differed in their education and income levels.
The researchers also controlled for differences in 10 different social and biological variables that might contribute to the IQ increase including family income at birth, parental schooling, genomic ancestry, maternal smoking during pregnancy, maternal age, birthweight, and delivery type.
They found a strong correlation between the duration of breast feeding and long-term IQ and income benefits as adults. The link appears to be from the nutrients found in breast milk.
According to lead author Dr Bernardo Lessa Horta, "The likely mechanism underlying the beneficial effects of breast milk on intelligence is the presence of long-chain saturated fatty acids (DHAs) found in breast milk, which are essential for brain development. Our finding that predominant breastfeeding is positively related to IQ in adulthood also suggests that the amount of milk consumed plays a role.”
The effects that the researchers have found are correlational. They have shown that breast feeding is linked to higher IQ as an adult and they have tried to control for differences in other factors that might affect adult IQ rates. They haven’t, however, proven that breast feeding causes children to develop higher IQ as adults. It is virtually impossible to control for all the genetic and environmental differences that could have affected the adult IQ of their study population.
This research is an interesting addition to our understanding of the long-term effects of breastfeeding. However, we need a lot more research before we can make a claim that breast feeding will make you smarter.
*Sive Finlay: Zoologist and researcher for Futureproof, @SiveFinlay