The primary sugar found in milk is the disaccharide, lactose. In normal human digestion, lactose is broken down into two monosaccharides: glucose and galactose. Approximately 20% of the general population, however, is unable to adequately digest lactose. Until recently, lactose intolerant individuals have had to avoid airy foods or suffer painful gastrointestinal symptoms. Today, lactose reduced milk and reduced calorie lactose free yogurt are commercially available. These products are often manufactured by the enzymatic hydrolysis of lactose, using the enzyme lactase.