Breast is best is the mantra of most major medical organizations. Women have it drummed into them well before giving birth. As a result, women for whom breastfeeding is not working often make themselves miserable pumping round the clock trying desperately to get their babies this “liquid gold”.
It is unfortunate, especially since despite all the hype, the best research does not find longterm benefits of breastfeeding.
Here’s the thing about those oft-stated benefits to IQ, obesity, and allergies and asthma: They only show up observational studies.
Why does that matter? Because observational studies of breastfeeding all suffer from the same huge flaw: Breastfed infants tend to differ from formula-fed infants not just in how they are fed in infancy, but in nearly every other possible way–in their mother’s education level, in their mother’s IQ, poverty, neighborhood safety, exposure to environmental toxins, race, and type and quality of childcare. In scientific terms, breastfeeding is confounded, out the wazoo.
We cannot tell which benefits found in an observational study derive from breastfeeding rather than from the myriad other advantages linked with breastfeeding.
(The “good” observational studies attempt to control statistically for the other relative advantages of breastfed infants. Unfortunately, controlling for confounds only works well when (1) all the important potential confounds are known, and (2) when there is sizeable overlap between the compared groups. Neither is true when it comes to breastfeeding.)
In an ideal world, we would settle this question by conducting several large randomized controlled trials (RCTs), in which new mothers would be randomly assigned to breastfeed. RCTs are the gold standard in medicine for determining whether a true cause and effect relationship exists. In practice, though, such trials are neither feasible nor ethical.
Fortunately, we have the next best thing: a handful of studies that have cleverly circumvented the problem of confounding. These fall into two categories:
- sibling studies, which compare siblings from the same families who were breastfed for different lengths of time, or who were not both breastfed.
- a large RCT of a highly successful breastfeeding intervention (PROBIT Trial).
(Is the PROBIT Trial an exception to the no-RCT rule? No. Women in the PROBIT trial were not randomly assigned to breastfed or not; they were randomly assigned to receive a breastfeeding intervention or not.)
After my friend and I spoke about his irritation with the medical organizations like the American Academy of Pediatrics (AAP) and NHS overstating the benefits of breastfeeding, I was dissatisfied with my vague sense that he was right. I wanted to know exactly which benefits had been oversold and exactly which were supported not just by observational studies but by better-designed studies.
The short answer: Nearly all the alleged long-term benefits are likely the result of confounding, not breastfeeding. Better-designed studies find only a handful of real benefits: a reduced chance of severe gastrointestinal infections and a lower risk of eczema during infancy, and perhaps a small boost in childhood IQ.
Alleged Breastfeeding Benefits According to the NHS
According to the NHS, breastfed infants are…
- less likely to suffer from vomiting or diarrhea and therefore less likely to go to hospital
- less likely to develop type 2 diabetes in later life
- less likely to become obese in later life
- less likely to suffer from heart disease in later life
- less likely to suffer from constipation
- less likely to get a chest or ear infection and therefore less likely to go to hospital
- less likely to suffer from tooth development problems
- more likely to have good communication and speech skills
- more likely to have good circulation
- less likely to suffer from wind, colic and constipation
- less likely to develop eczema or asthma
Sounds pretty impressive, right? Until you set aside the evidence from observational studies…
Continue reading “Breastfeeding benefits: The real, the imagined, and the exaggerated”