When it comes to nutrition for infants, the medical community largely agrees that "breast is best." But a new study in siblings seeking to uncover potential biases suggests breast-feeding may be no more beneficial than bottle-feeding for many long-term health outcomes.
The research, led by Cynthia Colen, assistant professor of sociology at Ohio State University, was recently published in the journal Social Science & Medicine.
Colen says that previous studies on the topic fall prey to selection bias, in that 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."
In the latest study, the team included an analysis of outcomes from families of different races and socioeconomic backgrounds for comparison and found that their results matched those of other studies advocating that the benefits of breast-feeding outweigh those of bottle-feeding.
The researchers also assessed health and education benefits of the different feeding approaches for children between the ages of 4 and 14 years old, which extends beyond the typical immediate benefits studied in past studies.
Colen says the declaration from federal officials that breast-feeding for the first 6 months of an infant's life is a national priority could stigmatize women who are not able to breast-feed their babies. She adds:
"I'm not saying breast-feeding is not beneficial, especially for boosting nutrition and immunity in newborns. 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."
Colen notes that typically, more advantaged moms are able to select into breast-feeding, which makes it difficult to understand what affects certain outcomes, such as obesity. "Is it breast-feeding itself," she questions, "or those other background characteristics?"
Breast-feeding's effects 'not statistically significant'
The researchers analyzed data from the 1979 cohort of the National Longitudinal Survey of Youth (NLSY) - a national sample of young men and women 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 new study questions potential biases in previous studies that assert breast-feeding's positive outcomes are better than those of bottle-feeding.
All children were between the ages of 4 and 14 years old during the time period studied, and about 25% of the siblings in the data were differently fed within the same family. In other words, one sibling was breast-fed while another was bottle-fed.
The team wanted to answer two simple questions:
- Was at least one child breast-fed?
- If so, what was the duration of breast-feeding?
In total, the study measured 11 outcomes common to other breast-feeding studies, including body mass index (BMI), obesity, asthma and hyperactivity. It also measured scores predicting academic achievement and scholastic competence.
Overall results showed the same results of other studies; namely, that breast-feeding results in better outcomes than bottle-feeding in a number of measures.
However, when the team restricted the sample to siblings who were fed differently within the same families, the scores showing breast-feeding's positive effects on 10 of the 11 measures for child health and well-being were not statistically significant, the researchers say.
"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 says.
She notes that if long-term outcomes are not necessarily as affected by breast-feeding as we currently believe they are, it may be time to address other impacting issues, such as school quality, housing and parental employment.
"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."
In 2013, Medical News Today reported on a study that suggested outgoing mothers are more likely to breast-feed.