News Blog readers will have seen a short report on the Lancet article from Brazil associating breastfeeding with improved IQ. Alas, probably not correct: at least any effect must be very small, according to a recent article that greatly improves on the Lancet paper. First, the authors cite a thorough systematic review published in BMJ Open  and conclude that “Any observed associations are best explained by residual confounding.” Second, they conduct an observational analysis of nearly 12,000 children from the Twins Early Development Study. They find that breastfed girls, but not boys, have a significant, but very small, increase in IQ at age 2. They also find that the slope of the increase in IQ beyond age 2 is unaffected by whether or not the child was breastfed. They conclude that, while science cannot exclude tiny effects, the evidence for an effect of breastfeeding on IQ is very weak. Most studies show that the effect goes away or rapidly attenuates as adjustments are made for known confounders. These results are consistent with various experimental studies of nutritional supplements in early life, where null results contrast with positive results from social and educational interventions.
— Richard Lilford, CLAHRC WM Director
- Victoria CG, et al. Association between breastfeeding and intelligence, educational attainment, and income at 30 years of age: a prospective birth cohort study from Brazil. Lancet Glob Health. 2015; 3(4): e199-205.
- von Stumm S & Plomin R. Breastfeeding and IQ Growth from Toddlerhood through Adolescence. PLoS One. 2015. [ePub].
- Walfisch A, Sermer C, Cressman A, Koren G. Breast milk and cognitive development – the role of confounders: a systematic review. BMJ Open 2013; 3: e003259.