Lactose intolerance is a condition in which a person feels discomfort after eating or drinking dairy products. Some symptoms of lactose intolerance include bloating, stomach pain, flatulence (excessive gas in the intestines), and diarrhea. Symptoms usually occur about 30 minutes to 2 hours after consuming dairy products. They are caused by an excess of the carbohydrate lactose in the digestive system. Lactose is found in dairy products, including milk, ice cream, and cheese. It is also called milk sugar.
Lactose is broken down in the small intestine by an enzyme called lactase. During childhood, most people produce enough lactase. But many people produce less as they grow older. If they consume dairy foods, the lactose is not broken down. It thus passes into the large intestine. Bacteria in the large intestine feed on the lactose, causing gas and other symptoms. Lactase production can also be decreased by damage to the lining of the small intestine. Such damage may result from medications, disease, surgery, or radiation.
Lactose intolerance is more common in people with Asian, African, Native American, or Mediterranean ancestry. It is less common among people from cultures with a history of dairying. Most people with lactose intolerance can drink small amounts of milk. They can also enjoy yogurt, which has little lactose. People may improve their tolerance for lactose by regularly eating small portions of dairy foods with meals. This can help bacteria in the large intestine adapt to lactose over time. People may also use lactose-free milk products or lactase supplements.
See also Milk (Milk in the human diet) .
