Determinants of colostrum and breast milk immune composition and consequences for infant health

Abstract

Background: Breast milk is the principal source of nutrition during a critical period of immune programming - maternal and environmental exposures may influence breast milk composition and infant health. Objectives: To examine whether environmental and/or maternal factors influence levels of immune active components in colostrum and breast milk and identify associations between these factors and health outcomes. To examine if colostrum/breast milk immune composition can be grouped into specific 'lactotypes'. Methods: A prospective cohort study of mother/infant pairs in London, Moscow and Verona. Colostrum samples (days 0-6) and Mature Breast Milk (4-6 weeks) were analysed in duplicate using electrochemiluminescence, and the relationship between levels of immune active factors and maternal/environmental/infant factors was evaluated using mixed models. Lactotypes were identified using Principal Components Analysis. Results: Levels of immune active cytokines and growth factors in colostrum declined rapidly over time (r=-0.39 to -0.16; p<0.01). The effect of time could not be corrected using total protein or sodium as correction factors, due to different kinetics for each mediator measured. There were significant differences in colostrum and breast milk composition between countries, which could not be explained by the environmental and maternal factors examined.

Using PCA there were two clusters of mediators, suggesting that four human breast milk ‘lactotypes’ exist, based on immune composition. There was some evidence in support of a relationship between human milk mediator levels and/or lactotypes, and infant health outcomes. Conclusions: The data support an important role for breast milk cytokines, and especially growth factor, levels as determinants of infant health. Further work is needed to identify improved methods for analysing colostrum and mature milk composition, which account for time of collection and/or stage of lactation.