Biology and origin of bioactive peptides in milk

Abstract

Milk is now recognized as containing an array of bioactivities that dramatically extend the range of influence of mother over young beyond simple nutrition. The bioactivities in milk include modulators of digestive and gastrointestinal (GI) functions, hemodynamic modulators with potential effects on the GI tract, hormones and growth factors likely involved in mammary gland or infant development, immunoregulation, and nonimmune disease defense and microbial control. The bioactivities of milk vary with differentiation or functional state, or intramammary infection, of the mammary gland. Many bioactivities of milk are latent, requiring proteolytic activity for release of bioactive peptides from inactive native milk proteins. Hence their manifestation is dependent on both mammary state and protease activity at a target tissue site such as the GI tract of the suckling. Additionally, many bioactivities of milk result from interaction of peptide or protein and non-peptide components of milk. The complexity of interaction and developmental regulation of bioactivities in milk makes their understanding difficult, but allows for exquisite regulation and communication between mother and young.