The human digestive system breaks down food through a series of organs. Food enters the mouth where it is chewed and enzymes in saliva begin breaking it down. It then moves to the stomach through the esophagus where it is further broken down by acid. Most nutrients are absorbed in the small intestine due to its large surface area. The large intestine absorbs remaining nutrients and water before waste is eliminated. A balanced diet incorporating a variety of foods helps meet nutrient needs.