Breastfeeding longer may contribute to later success, study finds

Kokeb Negussie breastfeeding her son Moges (©UNICEF Ethiopia/2012/Getachew)

A new study from Brazil shows that children who breastfed longer had higher IQs, and overall improved socioeconomic status. While grabbing big headlines as a simple solution to child development, some question the focus on IQ as an accurate measure of the known lifelong effects of breastfeeding.

Researchers tracked breastfeeding rates for thousands of babies over the past 30 years. Their findings were published in the well-regarded British health journal The Lancet. A follow up interview and IQ test with 3,493of now 30-year-olds showed longer breastfeeding was connected to higher levels of education, better IQ test results and higher incomes. The big news is that the breastfeeding associated improvements occurred across socioeconomic status.

“Our study provides the first evidence that prolonged breastfeeding not only increases intelligence until at least the age of 30 years but also has an impact both at an individual and societal level by improving educational attainment and earning ability,” said the study’s lead author, Dr. Bernardo Horta in a press release.

It joins other studies that demonstrate the powerful impact of breastfeeding on child development. The authors found that breastfeeding for one year or more saw IQs increases of up by four points, an average of one year more of schooling and monthly incomes higher by 341 reais, compared to children breastfed less than one month. The rise in IQ was found to be responsible for more than 70 percent of the effect on income growth.

The research team controlled for 10 factors that also can contribute to better intelligence and life outcomes, such as economic status of parents, age of mothers when giving birth, type of delivery, schooling level of parents and more.

All signs point towards breastfeeding as a sure-fire way to improve child outcomes. But neuroscientist Dean Burnett is not entirely convinced.

“There are still plenty of other things that could be causing the pattern though, although it would be a huge ask to insist that a study of this size rules out every possible alternative,” he wrote, in the Guardian, about the study. “That’s the downside of studies into subjects like this; large groups of humans are mind-bogglingly complicated and persistently thwart our nice clean scientific methods.”

He concedes that there is evidence connecting brain development in infants and breast milk. But has issues with the use of IQ, for example, as a measure of intelligence. Debates for years have questioned whether tests that measure IQ actually indicate intelligence or social status. He also brings up the fact that breastfeeding is not actually all that simple of a solution. There are issues of stigma to consider, as well as the burden exclusive breastfeeding places on mothers.

It is a similar idea that NYU global health researcher Karen Grepin pushed back against in a 2012 blog post.

“Most public health experts recommend mothers to ‘exclusively’ breastfeed their children for six months. But that means that the mother can never very far from their baby this entire time. The fact that this might negatively impact a mother’s labor force participation or productivity seems completely ignored in these cost-effectiveness calculations,” wrote Grepin.

There are concerns that improperly wielding the findings of the results will increase stigma against mothers who do not breastfeed. The authors are keenly aware of this concern and have a more tempered view of their own results.

“I don’t want to terrify people who did not breastfeed or who breastfed for a short time,” said Horta to the New York Times. “It isn’t only breastfeeding that affects IQ and income. But our study does show that breastfeeding is important and should be encouraged.”

The bottom line is that breastfeeding is good for child health. Something that is well known and proven. The extent of its effects on long term child development is uncertain, but there is now reason to think it is positive. However, there are still many things that contribute to whether a child succeeds later in life.

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Tom Murphy

Tom Murphy is a New Hampshire-based reporter for Humanosphere. Before joining Humanosphere, Tom founded and edited the aid blog A View From the Cave. His work has appeared in Foreign Policy, the Huffington Post, the Guardian, GlobalPost and Christian Science Monitor. He tweets at @viewfromthecave. Contact him at tmurphy[at]humanosphere.org.