Digestion is the process that breaks down food into a form that can be absorbed into the bloodstream, so that the body can use it for energy and to build and repair tissues. Digestion begins in the mouth, with the action of saliva on food, but most of it takes place in the stomach and the small intestine. Practitioners agree that a healthy digestive system is a crucial factor in maintaining general physical and emotional well-being. Digestive-system disorders result from a number of causes, including a poor diet, emotional disturbances, inherited problems, allergies and infections.

Complementary treatments pay attention to diet and the state of the gut, usually by the elimination of waste products, supporting the liver and cleansing the colon. Therapies also seek to restore natural levels of the gut's beneficial bacteria, and identify and eliminate foods that irritate the digestive tract.