Thirty to 50 million Americans are lactose intolerant, according to Children's Hospital Boston. Symptoms may range from mild to severe but in all cases, individuals react to the lactose sugar in milk and other dairy products. Lactose intolerance primarily affects the gastrointestinal system. Over time, a decrease in dairy foods may also cause nutritional deficiencies.
Digestion
Lactose is a sugar found in milk. In most individuals, lactose is broken down in the intestine by the enzyme, lactase, to yield glucose and galactose. People with insufficient lactase cannot digest and absorb lactose. The undigested lactose passes into the intestines where the normal intestinal bacteria break down some of the sugar. The rest ferment and release carbon dioxide, the gas that causes bloating, diarrhea and abdominal pain.
Contrast With Allergy
Lactose intolerance is a condition that affects the digestive system and causes gastrointestinal symptoms. A milk protein allergy can also produce these symptoms. However, milk allergy is an immune response that triggers the release of antibodies and histamine into the circulation. For this reason, an allergy can also affect the respiratory system and skin. Wheezing, coughing, sneezing, hives and rash are common signs of milk allergy.
Underlying Conditions
In general, the body produces less lactase as it grows older. Therefore lactose intolerance is more frequent in older adults. In young children, lactose intolerance may result from a digestive disorder or from an injury to the small intestine that reduces the ability of the cells to produce sufficient lactase.
Vitamin and Mineral Deficiencies
Lactose intolerance may lead to calcium and vitamin D deficiencies if dairy foods are eliminated from the diet. Children with lactose intolerance should continue eating small amounts of dairy foods to obtain these essential nutrients, according to Children's Hospital Boston. Some patients are able to tolerate yogurt and cheese or small servings of milk. Other sources of calcium include green, leafy vegetables and vitamin D may be found in fish, fortified juice and fortified cereals.
