The gut harbors more than 600 different species of bacteria, contains over 20 different hormones, digests and absorbs the vast majority of nutrients, and accounts for 20% of body energy expenditure. It is also the largest immune organ in the body (Kraehenbuhl and Neutra, 1992). Thus, anything that affects the health of the gut will undoubtedly influence the animal as a whole and consequently alter its nutrient uptake and requirements. Gut health is a complex term that can include the macro- and micro structural integrity of the gut, the balance of the micro flora, and the status of the immune system. Further complexity arises because of their interactions and the resulting changes in gene expression and possibly endocrine regulation. This, in turn, may affect the way nutrients are partitioned and utilized for organ development, tissue growth and immune system maturation (Kelly and Conway, 2001; Kelly and King, 2001). This paper will attempt to discuss the link between gut health and nutrition, mainly using data generated in poultry studies.