Physiological basis of food intolerance in VLBW.

To provide an overview on the role of gut immunity, nervous system and motility patterns in the development of feeding intolerance in newborns. Maturation of the GI is important not only for digestion and absorption, but for endocrine and exocrine function as well. There is little data available about the development of the motility function and of the mucosal barrier of the human gut, and in particular about the motility patterns and mucosal changes in newborns during early days of life. It is known that functional maturation of the gastrointestinal tract is quite different over time with respect to its anatomical development. Besides, the gastrointestinal tract through innate and specific immunologic factors, acts as a defense against ingested antigens. In addition to the mucous membrane integrity and digestion, numerous specific immunologic cells and mediators orchestrate such defensive mechanisms. In case of food antigens, the outcome is usually in favor of tolerance. Defects in that barrier, however, can lead to the development of aberrant immunologic responses, including hypersensitivity reactions. It is obvious that an appropriate feeding regimen during early infancy is in favor of food tolerance. However, in addition to genetic predisposition, development of tolerance is facilitated by an adequate gut barrier (immune or nonimmune), well-coordinated GI motility and nervous network, and appropriate food regimen.