As many as 30 to 50 million Americans have some degree of lactose intolerance. It is most common in African Americans, Asians, Native Americans and people of Mediterranean origin. Problems caused by lactose intolerance range from mild stomach upset, swelling, and gas, to nausea, stomach cramps and diarrhea. Symptoms may last as long as 10 to 12 hours. The severity of symptoms depends on how sensitive you are to lactose and how much lactose you eat.
Some people can tolerate small amounts of dairy products eaten throughout the day.
However, drinking a large glass of milk or eating a lot of cheese may cause some of the symptoms described. If gas, bloating, diarrhea, or other symptoms occur, limit those foods. Remember, foods acceptable for some people may not be well-tolerated by others. Products such as Lactaid milk, cheese and cottage cheese contain lactase, the substance needed to break down lactose. Many people with lactose intolerance are able to eat these foods without side effects.