Human Milk Research, More to Learn?

Human milk is the recommended sole source of nutrition for infants during the first 6 months of age, thanks to its composition rich in nutritious and bioactive components. Progress in analytics has allowed for a detailed description of its components and their variability within and among mothers. This is especially valid for the human milk oligosaccharides (HMOs) that represent one of the major human milk compound groups. The stages of lactation and maternal genotypes are the main contributors to the variability of HMOs, although other maternal and environmental factors also contribute to the variation, which may be important for adaptation in evolutionary terms. Today, mainly individual HMOs or structural groups of HMOs were associated with infant outcome measures, ranging from anthropometry to immunity and brain development (social and cognitive skills). Mechanistic insights can partly explain some findings, yet there is a lack of consistency between the different observational studies of breastfed infants. Gaining a better understanding of the reasons behind these disparate findings is the key element going forward. Furthermore, studying human milk components, like HMOs, and their expected benefits using a systems biology approach can reveal further important insights. Here, we discuss recent findings with the perspective to learn more about the link to health outcomes.