Milk has often been touted as the perfect food-designed by Mother Nature not just to nourish the newborn but, as we now know, to "educate" them through various mechanisms for promoting infant health (1). For example, human milk contains an array of complex oligosaccharides known to promote beneficial intestinal microbiota colonization and bioactive peptides that exhibit a range of biological activities from neuroactive to antimicrobial. These peptides are generally encrypted in larger proteins that are released only following hydrolysis during intestinal digestion (2). Milk contains 2 major protein groups, caseins and whey proteins, the latter of which is traditionally a valuable by-product of cheesemaking. Both types are highly valuable protein sources for human nutrition and are also major potential sources of bioactive peptides that can elicit a variety of physiologic effects in humans. However, most studies to date (including those from our own group) have concentrated on the in vitro bioactivity of isolated peptides and then speculated on a potential role in human health, nutrition, and disease. In contrast, there are only a few examples in which digestion of milk protein has been studied in detail in vivo in humans (3, 4). In this sense, what happens during digestion within the milieu of the human intestine has been more of a "black box" given the sheer number and bioactivity of peptides that could be generated from complex protein sources such as milk.
展开▼
