The alkaline digestive secretion produced by glands in the lining of the small intestine. Rich in water, mucus, and a suite of enzymes including peptidases, sucrase, lactase, maltase, and intestinal lipase, it completes the chemical breakdown of proteins, carbohydrates, and fats into absorbable units. Its alkaline pH neutralises the acidic chyme arriving from the stomach, creating conditions in which both the intestinal enzymes and pancreatic enzymes work effectively. The secretion is stimulated by the presence of food and by hormonal signals. Disorders that reduce intestinal juice output impair nutrient absorption and can lead to deficiencies. It works in concert with bile and pancreatic juice during the main phase of digestion.