The human milk microbiome and oligosaccharides - What's normal and so what?

Abstract Text:

Human milk is inarguably the only food "designed" to be consumed exclusively by humans - providing all the essential nutrients (and other bioactive compounds and constituents) needed for growth and development of the human infant. As such, understanding human milk composition and variation, therein, is critical to optimizing human health during this vulnerable time, particularly in the most at-risk infants. More complete characterization of human milk composition may also lend important insight as to what constitutes optimal nutrition in other phases of the lifecycle, not only for the human host but also for the myriad commensal, mutualistic, and sometimes pathologic microbes with which we coexist. However, our understanding of human milk composition and its impact on host and microbial health is far from complete. For instance, until recent advances in instrumentation allowing the detection and identification of difficult-to-culture bacteria, common dogma was that human milk was sterile unless produced by an infected mammary gland or contaminated after expression. As such, focus on the roles played by complex (an indigestible) human milk oligosaccharides (HMO) has been directed exclusively toward those related to the recipient infant and his/her gastrointestinal microbiota - roles that are without a doubt important for infant health. We now know that human milk contains a diverse population of bacteria. As such, we and others postulate that HMO may impact the microbial communities present in milk and the mammary gland producing it. Here we will briefly describe what is currently known about variation in the human milk microbiome and HMO as well as relationships among maternal diet, milk composition (including microbes and HMO), and the infant gastrointestinal microbiome. In addition, we will introduce an ongoing cross-cutting study funded by the Integrated National Science Foundation Support Promoting Interdisciplinary Research and Education (INSPIRE) mechanism designed to help us better understand what is normal in terms of milk microbes, HMO, and infant fecal microbiome in various locations worldwide. The importance of cooperation and interdisciplinary discussion around methods and vocabulary will be discussed as will some of the challenges faced in terms of sample collection, storage, transport, and data analysis. Finally, selected preliminary data from the INSPIRE study and a framework for considerations for future studies designed to use big (and interdisciplinary) data to understand variation in global milk composition and how this is related to infant health will be presented.

Keywords: human milk, microbiome, oligosaccharides, HMO, health, development