Lactose intolerance is a condition also known as intolerance to milk. To be more precise, it is intolerance to milk sugar, lactose. In European population, it affects approximately ten percent of people. However, in native Africans and Asians, lactose intolerance affects more than half of the adult population.
The problem is in the small intestine. Lactose can not be absorbed by the intestine, but cells of small intestinal mucosa have an enzyme called lactase, which splits the lactose to two other sugars - glucose and galactose. These sugars have a simpler structure and they are well-absorbable. People with lactose intolerance have some disorder of the lactase enzyme and they are unable to split the lactose molecules. The enzyme may be absent due to a genetically inherited defect, which is rare, or be damaged by many local pathological conditions, typically an inflammation. Such secondary absence of lactase is often found in patients with celiac disease. The majority of adult cases, however, are related to a quite natural decrease of lactase function that comes with age.
The lactose can not be split and stays in the intestines. The accumulation of osmotic active molecules draws water into the intestines and bacteria living in the large intestine convert it to other metabolic products including gases. After the intake of milk or some other diary products, the patient suffers from acute diarrhea, flatulence and abdominal pain. Prolonged diarrhea may result in failure of absorption of some nutrients.
If lactose intolerance is genetically determined, it can not be avoided. Patients with secondary lactose intolerance due to celiac disease may prevent symptoms of lactose intolerance by a strong adherence to proper celiac diet.
The patient should not drink milk but so he loses an important source of calcium. Therefore, it is advisable to regularly take calcium supplements or eat and drink fermented milk products with a low content of lactose. In some cases, the lactase enzyme may be administered in form of a pill.