Nutrition and Early Life Immune Health

The primary role of the immune system is to provide protection against pathogens, but it is also important in achieving tolerance to harmless environmental exposures. There are a number of mechanisms by which diet and nutrition can influence the immune system: providing the necessary energy to support immune cells to function; as substrates for the synthesis of proteins, cells and other structures involved in the immune response; as essential components or cofactors of enzymes involved in the immune response; as precursors for immune signaling molecules; and via the microbiome. Some aspects of the immune system are poorly developed at birth indicating the importance of passive immunity from the mother (e.g., via breast milk) and immune maturation occurs over the first months to years of life. This maturation occurs alongside gut maturation and acquisition of a mature microbiome and is driven in part by factors derived from breast milk and, later on, from the diet but also by exposure to antigens of different kinds including from microbes. Consequently, immune function in early life is highly variable, and is under the influence of both genetic and environmental factors including mode of birth; exposure to immune active components within human breast milk, to antibiotics, and microbes; and the timing of solid food introduction. Observational and interventional studies have been undertaken to assess the immunomodulatory effect of a number of dietary components in early life, including omega-3 fatty acids, prebiotics, and probiotics. Some of these studies confirm significant effects of supplementation during pregnancy and/or early life in reducing the risk of both atopic and infectious disease, but the findings are not consistent across all studies and the extent and duration of the effects seen vary depending upon the duration and dose of supplementation and the established disease risk of the population. Ongoing research will require an integrated and collaborative scientific approach in order to capture all potential interactions between the maternal and infant diet, infant microbiome and the immune system in early life, and how these relate to disease risk.