A new study suggests that there is a link between prolonged breastfeeding and higher intelligence, extended schooling, and greater income as an adult.

Studies have focused on the short-term outcomes of breastfeeding children. Typically, exclusive breastfeeding is suggested for approximately the first six months after birth.

"The effect of breastfeeding on brain development and child intelligence is well established, but whether these effects persist into adulthood is less clear," says lead author Dr. Bernardo Lessa Horta of Federal University of Pelotas in Brazil.

Published in The Lancer Health, the researchers tracked 3,493 participants born in Pelotas, Brazil for 30 years. The participants were separated into five groups, varying on the amount of time spent being breastfed. They were also controlled to answer to ten variables IQ like family income at birth, maternal age, and academic achievements.

Compared to the participants who were breastfed for less than one month as an infant, the participants who were breastfed for four months had four more IQ points, 0.9 more years of schooling, and earned an average of $104 per month more.

Dr. Horta suggested there is a biological mechanism that may take place to why breast milk is ideal. He believes the long-chain saturated fatty acids (DHAs) found in breast milk helps increase intelligence because DHAs are essential for brain development. The group found a positive correlation between IQ in adulthood and the amount of breast milk consumed.

A critique of the study was that the researchers did not evaluate the state of the participants' home environment for an infant or the maternal-infant relationship. The researchers say that breastfed subjects have demonstrated improved cognitive functioning even after controlling for a home environment and parental stimulation.

Other studies argue a potential confounding factor that mothers who breastfeed for longer periods are typically of higher socioeconomic positions. Also, studies argue that mothers of higher socioeconomic status have more access to health care, which may lead to overemphasizing the health benefits of breastfeeding. Dr. Horta responds:

"What is unique about this study is the fact that, in the population we studied, breastfeeding was not more common among highly educated, high-income women, but was evenly distributed by social class," Dr. Horta explains.

Breastfeeding children may have other benefits as being more likely to host healthy gut bacteria. Click here to find out more.