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Babies who are breastfed for at least a year grow up to be significantly more intelligent as adults and they earn more money, too, a new study shows.
The findings fit in with many other studies that show breastfeeding helps brains to develop better. But this study was done in an unusual way, following people from birth until they were 30 years old, to see how they did in life.
The breast-fed babies did better than babies who were nursed for a month or less, the researchers report in the journal Lancet Global Health.
They scored better on intelligence tests as adults and they also earned more on average.
Dr. Bernardo Lessa Horta from the Federal University of Pelotas in Brazil says breastfeeding is not only good for babies, but for society in general.
“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,” Horta said in a statement.
The team’s been following nearly 6,000 people born in Pelotas, Brazil in 1982. It’s considered a good study because it’s what is called prospective — information on all sorts of things from breastfeeding to how much the babies weighed at birth was gathered at the time. People were not asked to remember what they did years later.
Then, the children were followed as they grew up. When 3,500 of them were about 30, they were given intelligence tests and asked about their earnings.
“Participants who were breastfed for 12 months or more had higher IQ scores (difference of 3·76 points), more years of education and higher monthly incomes than did those who were breastfed for less than 1 month,” the researchers wrote. Babies breastfed for a year or longer earned about a third more.
“The results of our mediation analysis suggested that IQ was responsible for 72 percent of the effect on income," the researchers added.
In the U.S. about half of new moms breastfeed, surveys show.
Many experts have questioned whether it’s breastfeeding that makes babies grow up healthier and smarter, or something else that their mothers do — maybe spending more time with them. In other studies done in the U.S. and Europe, mothers who breastfeed longer tend to be more educated and affluent — and that clearly has an effect on their kids.
This study was different.
“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,” Horta said.
“Previous studies from developed countries have been criticized for failing to disentangle the effect of breastfeeding from that of socioeconomic advantage, but our work addresses this issue for the first time.”
They also took into account how long the parents went to school, genomic ancestry, whether mothers smoked during pregnancy, the mothers’ ages, birthweight, and delivery type.
Breastfeeding clearly came out as a major factor.
It’s probably the nutrition found in human milk, Horta said. “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,” he said.
“Our finding that predominant breastfeeding is positively related to IQ in adulthood also suggests that the amount of milk consumed plays a role.”
The American Academy of Pediatrics recommends that newborns get nothing but breast milk until they are six months old. The AAP recommends that mothers continue to breastfeed, along with giving other food, after six months for at least a year or even longer “as mutually desired by mother and infant.”