Evidence for the long-term benefits of breast-feeding — well beyond infancy — continue to grow. In the latest analysis of the academic performance of children who were breast- or bottle-fed, researchers found that breast-fed babies scored higher on tests of math, reading and writing skills at 10 years old, compared with those who were bottle-fed as babies.
In the latest trial, led by Wendy Oddy at University of Western Australia, more than 1,000 children were followed from before birth to age 10. The mothers were asked about whether they breast-fed their infants when their babies were 1, 2 and 3 years old; the children then took standardized national achievement tests in the third, fifth and seventh grades.
Oddy's group found that by age 10, the children who were breast-fed for six months or longer scored 16 points higher on these tests than those were not breast-fed: babies who breast-fed scored 18 points higher in reading and writing skills, and 16 points higher in spelling.
“Breast-feeding may influence children's academic achievement through brain development and general health,” Oddy said in an email interview. “We think that the improved cognitive differences between breast- and formula-fed infants was due to unique constituents of breast milk.”
Breast milk, she says, is loaded with nutrients that are known to enhance brain development, such as omega-3 fatty acids, which are not always included in formula. In brain studies of infants, scientists have found higher levels of omega-3 fats in the cortex of babies who were breast-fed compared with those who received formula.
Oddy's findings support the recommendations of both the World Health Organization and the American Academy of Pediatrics, which advise new mothers to breast-feed infants exclusively for at least six months.
Oddy's study further revealed that the benefit of extending breast-feeding time was particularly pronounced in boys. Compared with girls, boys who were breast-fed for more than six months scored even higher on academic tests a decade later. While the reasons for the gender difference aren't clear, previous studies offer some clues as to why boys may reap a bigger benefit. For instance, cognitive development in boys occurs more slowly than in girls, presumably because of girls' higher levels of the hormone estrogen, which can be protective of neural brain growth. Girls may also not be as negatively affected by maternal stress during pregnancy, according to some recent studies, while male fetuses may experience a shrinking of some brain regions due to an expectant mom's anxiety.
Finally, some less biological reasons may explain the differences in breast-feeding's effects on the genders. Some studies suggest that boys may be more dependent on the maternal bonding that occurs during breast-feeding than girls, and that this bonding is important for language acquisition and cognitive development. This interaction may explain why boys who were breast-fed longer enjoyed the greatest benefit in academic performance later in life.
Findings like Oddy's raise the inevitable question: are moms who choose not to breast-feed being reckless with their baby's care? “Not breast-feeding may be an irresponsible decision if a mother chooses to bottle-feed knowing the benefits of breast milk,” says Oddy. “But some women have difficulty with breast-feeding, so it is a complex issue. Women need support to breast-feed — support from their family, their partner and friends, society, the health system and community in general.”
In fact, the latest figures on breast-feeding confirm that while many new moms want to breast-feed, keeping it up often proves too challenging. According to the Centers for Disease Control and Prevention, 75% of newborns were breast-fed in their first month or so of life in 2007, while only 33% were being exclusively breast-fed at three months; by six months, only 13% were predominantly receiving breast milk. Nearly 40%, however, were getting breast milk supplemented with formula at this age.
Oddy notes that in order to breast-feed exclusively for the recommended six months, and for children to receive the full benefits of being breast-fed, mothers need support from health-care systems that teach and encourage breast-feeding, as well as assistance from family, friends and employers to make breast-feeding easier. The benefits, she says, are too strong ignore. “We must all be responsible for the promotion of the ‘best way to feed a baby,' from the mother's milk,” she said.