Exclusive human milk feeding for the first 6 months of life, with continued breastfeeding for
1 to 2 years of life or longer, is recognized as the normative standard for infant feeding.1,2
Human milk is uniquely suited to the human infant, both in its nutritional composition and
in the non-nutritive bioactive factors that promote survival and healthy development.3 Here,
we briefly review the nutritional composition of human milk and provide an overview of its
varied bioactive factors, which include cells, anti-infectious and anti-inflammatory agents,
growth factors, and prebiotics. Unlike infant formula, which is standardized within a very
narrow range of composition, human milk composition is dynamic, and varies within a feeding, diurnally, over lactation, and between mothers and populations. Influences on
compositional differences of human milk include maternal and environmental factors and
the expression and management of milk (e.g., its storage and pasteurization). Understanding
human milk composition provides an important tool for management of infant feeding,
particularly of fragile, high risk infants, and for understanding the potential impact of
storage and pasteurization on milk components. Further, we note some bioactive
components found in human milk that are being developed and tested for potential medical
applications as prophylactic or therapeutic agents.