Lactose is a sugar naturally found in dairy products like milk, butter, yogurt, and more. Learn which 5 foods to avoid for lactose intolerance. Lactose intolerance is a condition that makes it hard to digest the sugar in milk and milk products, called lactose. People with lactose intolerance often have diarrhea, gas and bloating after eating or drinking foods containing lactose. Lactose hides in more than just milk. Learn which dairy products, processed foods, drinks, and even medications contain lactose and how to spot it on labels. Lactose is sometimes referred to as “milk sugar” because it is only found naturally in the milk of mammals—including cows, goats and humans. Milk from cows and goats is used to make cheese and yogurt, but not all milk products contain the same amount of lactose. Lactose, carbohydrate containing one molecule of glucose and one of galactose linked together. Composing about 2 to 8 percent of the milk of all mammals, lactose is sometimes called milk sugar. Another reason is that lactose intolerance tends to be under-reported: most lactose-intolerant individuals can tolerate at least some lactose before they show symptoms, and their symptoms differ in severity. Find out about lactose intolerance, including symptoms, how it's diagnosed, treatment and what causes it. Lactose is a natural, complex sugar produced in all mammalian milk that’s difficult to breakdown unless you have lactase, a protein, in your small bowel. Lactose is a disaccharide composed of galactose and glucose, which form a β-1→4 glycosidic linkage. Its systematic name is β- D -galactopyranosyl- (1→4)- D -glucose. Lactose is a major disaccharide present in milk. It is composed of two simple sugars, glucose and galactose. Cow, goat, and buffalo milk contains less lactose than human milk. It has several applications in the food industry.