The effect of nutrition on gastrointestinal barrier function.

The tightly adherent monolayer of epithelial cells that line the luminal side of the intestine provides a dynamic and highly regulated barrier to the passive transport of macromolecules. The presence of both nutrients and microbes within the gastrointestinal lumen impose a dichotomous task to this epithelial barrier. Several lines of evidence suggest that conditions created in modern intensive care units (ICUs) dysregulate the discriminatory function of the epithelial barrier. Alterations in intestinal barrier function may result in permeation of autotoxic macromolecules of immense size and diversity that normally reside in the gut lumen. It is becoming increasingly recognized that artificial nutritional support of the critically ill patient may result in significant alterations in epithelial barrier function. The causes and consequences of diet-induced alterations in the gastrointestinal barrier will be discussed. Future strategies in the development of more physiological diets for the critically ill will likely involve the addition of neural, hormonal, and growth factors as stimulants for enhancement of barrier function.