Response to Reviewers

Although observational findings linking breast milk to higher scores on cognitive tests may beconfounded by factors associated with mothers’ choice to breastfeed, it has been suggested thatone or more constituents of breast milk facilitate cognitive development, particularly in preterms.Because cognitive scores are related to head size, we hypothesised that breast milk mediatescognitive effects by affecting brain growth. We used detailed data from a randomized feedingtrial to calculate percentage of breast milk (%EBM) in the infant diet of 50 adolescents. MRI scans were obtained (mean age=15y9m), allowing volumes of total brain (TBV), white and greymatter (WMV, GMV) to be calculated. In the total group %EBM correlated significantly withVerbal IQ (VIQ); in boys, with all IQ scores, TBV and WMV. VIQ was, in turn, correlated withWMV and, in boys only, additionally with TBV. No significant relationships were seen in girlsor with grey matter. These data support the hypothesis that breast milk promotes braindevelopment, particularly white matter growth. The selective effect in males accords with animaland human evidence regarding gender effects of early diet. Our data have importantneurobiological and public health implications and identify areas for future mechanistic study.*Manuscript (cover page, abstract, abbreviations, text, references, and figure legends)Click here to view linked References