In an arti­cle the Royal Sta­tis­ti­cal Soci­ety announced as the runner-up in their annual Awards for Sta­tis­ti­cal Excel­lence in Jour­nal­ism, Helen Rum­be­low thor­oughly inves­ti­gates the well-debated sub­ject of breastfeeding.

The con­clu­sion of the piece is that much of the evi­dence in sup­port of breast­feed­ing is mas­sively mis­rep­re­sented or inher­ently flawed.

“The evi­dence to date sug­gests it prob­a­bly doesn’t make much dif­fer­ence if you breastfeed.” […]

“The con­clu­sion is that the evi­dence we have now is not com­pelling. It cer­tainly does not jus­tify the rhetoric,” [Amer­i­can aca­d­e­mic Joan Wolf] says. The prob­lem with the stud­ies is that it is very hard to sep­a­rate the ben­e­fits of the mother’s milk from the ben­e­fits of the kind of mother who chooses to breast­feed. In the UK, for exam­ple, the high­est class of women are 60 per cent more likely to breast­feed than the low­est, so it is not sur­pris­ing that research shows that breast­fed infants dis­play all the health and edu­ca­tional ben­e­fits they were born into. But even if edu­ca­tion, class and wealth is taken into account, there is known to be a big dif­fer­ence between the type of mother who fol­lows the advice of her doc­tor and breast­feeds, and the one that ignores it to give the bot­tle. In other words, breast­feed­ing stud­ies could sim­ply be show­ing what it’s like to grow up in a fam­ily that makes an effort to be healthy and respon­si­ble, as opposed to any­thing pos­i­tive in breast milk.

This is not to say that breast­feed­ing is not good:

  • Wolf acknowl­edges that it helps pre­vent gas­troin­testi­nal infec­tions (life-saving in the devel­op­ing world, gen­er­ally a mild com­plaint in the West).
  • Michael Kramer (one of the world’s most author­i­ta­tive sources of breast­feed­ing research; advi­sor to the WHO, Unicef and the Cochrane Library) believes:
    • The evi­dence is “encour­ag­ing” in pre­vent­ing res­pi­ra­tory problems.
    • The data on help­ing pre­vent breast can­cer is “solid”.

How­ever:

  • The data on obe­sity, aller­gies, asthma, leukaemia, lym­phoma, bowel dis­ease, type 1 dia­betes, heart dis­ease and blood pres­sure are “weak” at best.
  • The “highly respected” Amer­i­can Agency for Health­care Research and Qual­ity (AHRQ) warns that, “because the breast­feed­ing moth­ers were self-selecting, ‘one should not infer causality’”.
  • The World Health Organisation’s own research review con­cluded that gains were “mod­est” and also warned that “because none of the stud­ies it looked at dealt with the prob­lem of con­found­ing, the results could be explained by the ‘self-selection of breast­feed­ing mothers’”.

via @TimHarford