Arthur Eidelman deconstructs the latest breastfeeding-and-IQ study
Would you do a study that “analyzed” the relationship of breastfeeding and IQ based on data obtained from mothers who retrospectively reported at 18 months postpartum if they did or did not breastfeed? Would you conclude anything if the data base was a yes or no answer, with no distinction made if it was exclusive breastfeeding or partial (of any degree) and with absolutely no data provided as to duration of the breastfeeding? Believe or not that was the basis for the “conclusion” by researchers in England that was published in the open access journal PLOS/one, widely reported the lay press and trumpeted gleefully by the disparagers of breastfeeding.
No less than these glaring methodological deficiencies, is the misreading by the “public” of what the authors themselves studied. As they stated, the study was NOT on IQ per se, but rather on IQ growth trajectories. Or to put it simply, if breastfeeding increased a child’s IQ as measured by the initial IQ test and the child maintained that degree of increased IQ as compared to children who did not breastfeed, there would be no increased growth trajectory.
Thus, extrapolating from trajectory data to absolute levels of IQ and concluding that breastfeeding has no impact on IQ is just plain wrong (let alone ignoring the wealth of articles in literature that support the conclusion that breastfeeding does increase IQ : see the most recent review: Effects of Breastfeeding on Obesity and Intelligence: Causal Insights From Different Study Designs. Smithers LG, Kramer MS, Lynch JW. JAMA Pediatr. 2015 Aug)
Given this combination of the basic limitations of methodology coupled with the misinterpretation of the study results, one must conclude that in no way does this study contradict what is a given: breastfeeding is critical quantitative positive variable in the cognitive development of all children. Furthermore, as a measure of the limited value of the study, one should note that authors did not even cite the issue of the lack of data as to the quantity of breast milk that the infants ingested over time in their list of the limitations of the study, let alone, did they indicate the lack of data as to major confounders such as maternal IQ and quality of home environment.
Bottom line is that this study should be discounted in any serious discussion as to the relationship of breastfeeding and IQ!
Dr. Arthur I Eidelman is a Professor of Pediatrics at Shaare Zedek Medical Center, Jerusalem, Israel. He is the Editor-in-Chief of Breastfeeding Medicine, past president of ABM, and a Fellow of the Academy of Breastfeeding Medicine.
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