Breastfeeding, Human Milk and Allergic Disease: Findings from the CHILD Cohort Study ^†

Breastfeeding substantially contributes to infant microbiome and immune development, influencing lifelong health trajectories, including allergic disease risk. However, the nuances of these relationships and underlying mechanisms are not fully understood. The CHILD Cohort Study (www.childstudy.ca) follows 3500 Canadian families from pregnancy through adolescence to understand the developmental origins of asthma, allergies, and other chronic health conditions. Within CHILD, infant feeding practices (e.g., exclusivity, duration, and mode of human milk feeding) and human milk composition (e.g., microbiota, oligosaccharides, nutrients, and bioactive proteins) are studied to understand their contributions to infant microbiome development and health. CHILD findings show that breastfeeding shapes infant microbiome development [1,2,3,4] and serum immune biomarker profiles in the first year of life [5]. Breastfeeding appears to protect against childhood asthma in a dose-dependent manner that is strongest with direct nursing (vs. feeding pumped breastmilk) [6] and partially mediated through the nasal and gut microbiomes [7]. The combination of maternal peanut consumption and breastfeeding at the time of peanut introduction during infancy is associated with a lower risk of peanut sensitization through 5 years of age [8]. Using approaches to interrogate human milk as a complex biological system (rather than discrete individual components) [9,10], allergic disease phenotypes have been associated with specific combinations of human milk oligosaccharides [11], polyunsaturated fatty acids [12], and microbiota [13,14]. In conclusion, the CHILD Cohort Study has identified infant feeding practices, human milk components, and related biological mechanisms that may contribute to the development or prevention of allergic phenotypes. Expansion of this research could identify new therapeutic targets and disease prevention strategies.