Introduction

Food assimilation is the major function of the gastrointestinal tract, and important manifestations of many gastrointestinal diseases are their nutritional effects. Digestion and absorption of nutrients are discussed elsewhere. This chapter reviews physiologic considerations that are essential for planning proper nutritional management. The focus will be on the role of the liver in regulating the supply of carbohydrate and lipid fuels as well as ensuring the availability of essential substrates to peripheral tissues. The clinical features of malnutrition and specific effects of malnutrition on the gastrointestinal tract and liver will be discussed along with diet therapy in gastrointestinal disease. Finally, an approach to clinical nutrition will be presented, including nutritional assessment and the rational use of enteral and parenteral nutritional support.