Physiology of Digestion and Absorption: The Functional Interdependence Between Food and the Gut

This chapter starts with a brief description of the orchestration of upper GI function that enables food to be eaten and digested efficiently and safely. It then goes on to describe the close interrelationship between food and digestive function, such that an adequate supply of nutrients, particularly amino acids, is needed for the synthesis of digestive enzymes and mucosal absorptive cells in order to digest ingested food. From this one can appreciate the fact that malnutrition can induce GI dysfunction, as well as GI dysfunction can produce malnutrition through malabsorption. Finally, we discuss the unique nutritional needs of the colon that are provided by the microbiota. Consequently, to keep the colon healthy we need to keep the microbiota healthy with food that contains adequate supplies of complex carbohydrate residues (e.g., fiber) that are resistant to digestion and absorption by the small intestine.