In the Breastfeeding War, Objectivity Suffers

The passions of the breastfeeding war continue to spill into scientific publications. Another in a long line of publications documenting an association between breastfeeding and lower adiposity appeared this week in the Journal of Nutrition. The authors concluded:

These data confirm the importance of exclusive BF and prolonged BF for later cardiometabolic health.

But in fact, that’s not exactly true. As the authors note, “The observational design of the study does not allow inference of causality.” Yet they stuck an inference of causality into their conclusion.

In reality, the main contribution of this publication is to simply add to a bias of familiarity by repeating the assertion of a well-known association. The association between breastfeeding and lower obesity rates is largely explained by factors like education and social status that give people who are breastfed a lower risk of obesity to begin with. Correlation does not prove causation, no matter how often it’s repeated. But with enough repetition, people start assuming cause and effect has been established when in fact it has not.

All of this happens against the backdrop of a breastfeeding war between a passionate lobby for exclusive breastfeeding and the formula milk industry. McGill University professor Michael Kramer said in a 2010 interview for an article commended by the Royal Statistical Society:

When it becomes a crusade, people are not very rational. Breastfeeding advocates don’t need to overstate their case for issues that are more controversial, such as the link between breastfeeding and protection against obesity, allergies, and asthma. Public health bodies don’t have to exaggerate the benefits in order to be very comfortable about supporting breastfeeding.

And so, objectivity about breastfeeding as a strategy for reducing obesity is a casualty of this breastfeeding war. The CDC puts out posters like the one above, suggesting who-knows-what about the relationship between breastfeeding, ice cream sundaes, and childhood obesity.

Breastfeeding is a good idea. But as Brown University’s Emily Oster recently pointed out:

The popular perception that breast milk is some kind of magical substance that will lead your child to be healthy and brilliant is simply not correct.

Click here for the study from the Journal of Nutrition. Click here for more from RSS Statistical Excellence in Journalism and click here for more from Emily Oster.

Maternity, Painting by Meijer de Haan from WikiArt

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