The large intestine epithelium is a structure in rapid renewal. The main physiological function of this epithelium is the absorption of water and electrolytes by the absorbing colonocytes. This process of absorption and the anabolic metabolic pathways associated with the epithelium renewal require energy, which can be supplied from substrates present in both the arterial blood and in the luminal fluid. The fluid contained within the large intestine contain a high concentration of microorganisms forming the large intestine microbiota. Regarding nitrogen metabolism in the large intestine, between 4 and 12 g of undigested proteins are usually transferred from the small to the large intestine where they meet bacterial proteases and peptidases, which release peptides and amino acids. Amino acids are not absorbed to any significant extent by the large intestine epithelium but instead are used by the microorganisms for macromolecule synthesis, ATP production, and in diverse catabolic pathways leading to the synthesis of numerous metabolites. Among the metabolites released from amino acids by bacteria, we will examine in this chapter how short-chain fatty acids, lactate, and hydrogen sulfide are used as energy substrates by the absorptive colonocytes, and how these cells use glutamine from the arterial blood as main energy supplier.