Breast-Feeding Benefits Appear to Be Overstated
A new study comparing siblings who were fed differently during infancy suggests that breast-feeding may be no more beneficial than bottle-feeding for 10 of 11 long-term health and well-being outcomes in children aged 4 to 14. The study was published in Social Science & Medicine.
“Many previous studies suffer from selection bias. They either do not or cannot statistically control for factors such as race, age, family income, mother’s employment—things we know that can affect both breast-feeding and health outcomes,” says Cynthia Colen, PhD, MPH, an assistant professor of sociology at Ohio State University and the lead study author. “Moms with more resources, with higher levels of education and higher levels of income, and more flexibility in their daily schedules are more likely to breast-feed their children and do so for longer periods of time.”
Previous research has identified clear patterns of racial and socioeconomic disparities between women who breast-feed and those who don’t, complicating an already demanding choice for women who work outside the home at jobs with little flexibility and limited maternity leave.
Colen’s study also looks at health and education benefits of infant feeding practices for children aged 4 to 14 beyond the typical investigation of breast-feeding’s effects on infants and toddlers.
Federal health officials have declared breast-feeding for at least six months a national priority, which could end up stigmatizing women who can’t choose to nurse their babies, Colen says. “I’m not saying breast-feeding isn’t beneficial, especially for boosting nutrition and immunity in newborns,” she says. “But if we really want to improve maternal and child health in this country, let’s also focus on things that can really do that in the long term, like subsidized day care, better maternity leave policies, and more employment opportunities for low-income mothers that pay a living wage, for example.”
Demographic differences across families that can bias studies in favor of breast-feeding include parental race, age, marital status, family income, insurance coverage, the mother’s education and employment, and whether a woman smokes or drinks during pregnancy. “When we get more advantaged moms selecting breast-feeding, and we know those traits also will affect the health outcomes, it’s not clear what’s affecting an outcome like obesity: is it breast-feeding itself or those other background characteristics?” Colen says.
Researchers used data from the 1979 cohort of the National Longitudinal Survey of Youth (NLSY), a nationally representative sample of young men and women who were between the ages of 14 and 22 in 1979, as well as results from NLSY surveys between 1986 and 2010 of children born to women in the 1979 cohort. The children were between the ages of 4 and 14 during the time period studied.
Researchers analyzed three samples: 8,237 children; 7,319 siblings; and 1,773 discordant sibling pairs or children from 665 surveyed families in which at least one child was breast-fed and at least one other child was bottle-fed. The children who were differently fed in the same family represented about 25% of the siblings in the data.
The study measured 11 outcomes that are common to other breast-feeding studies: BMI, obesity, asthma, hyperactivity, parental attachment (secure emotional relationships between parents and child), and behavior compliance as well as scores predicting academic achievement in vocabulary, reading recognition, math ability, intelligence, and scholastic competence.
As expected, the analyses of the samples of adults and their children across families suggested that breast-feeding resulted in better outcomes than bottle-feeding in several measures. However, when the sample was restricted to siblings who were differently fed within the same families, scores reflecting breast-feeding’s positive effects on 10 of the 11 indicators of child health and well-being were closer to zero and not statistically significant.
In all samples, children who were breast-fed were at higher risk of asthma, which could relate to data generated by self-reports instead of actual diagnoses.
Some examples of differing benefits include the following:
• Breast-feeding’s beneficial influence on BMI decreased by 66% between siblings across families and siblings within families.
• The magnitude of the beneficial effects of breast-feeding for math, reading, vocabulary, and intelligence declined by 69% and 29%, respectively, when comparing data across families to data from within families.
“Instead of comparing across families, we are comparing within families, completely taking into account all of those characteristics—both measured and unmeasured—that differ by family, such as parental education, household income, and race/ethnicity,” Colen explains.
Differences between samples also were found in analyzing the effects of breast-feeding duration.
These findings have implications for health policy, she notes. “If breast-feeding doesn’t have the impact that we think it will have on long-term childhood outcomes, then even though it’s very important in the short term, we really need to focus on other things,” she says. “We need to look at school quality, adequate housing, and the type of employment parents have when their kids are growing up.
“We need to take a much more careful look at what happens past that first year of life and understand that breast-feeding might be very difficult, even untenable, for certain groups of women. Rather than placing the blame at their feet, let’s be more realistic about what breast-feeding does and doesn’t do.”
Source: Ohio State University