Lactose intolerance

Lactose intolerance Genetic testing and lactose intolerance

Milk is the first and most important nutritional ingredient for every baby and child, and it retains its nutritional value in the adult diet as well. It contains a balanced ratio of various substances such as protein, fat, carbohydrates, minerals and vitamins which are all essential for the proper development. Lactose is the principal carbohydrate (sugar) found in milk and dairy products. In the intestine, a special protein called lactase breaks it down to smaller parts (glucose and galactose) that can be absorbed by the human body through the intestinal mucosa and used as a cellular fuel. If for some reason the quantity of the lactase enzyme in the intestinal mucosa is decreased, a disorder called lactose intolerance develops.

More details about lactose intolerance

Due to the lack of lactase large quantities of undigested sugars pass through the small intestine to the colon where they are metabolised by the intestinal bacteria. Unabsorbed sugar is transformed by the bacteria into fats, gases and other bigger molecules. These bacterial metabolites cause the unpleasant symptoms of this disease.

The symptoms are very unspecific. Lactose intolerance can initially present as diarrhoea with abdominal bloating and possibly cramping as well. In the case of a severe exacerbation, nausea and vomiting can be present as well. The signs of disease appear from 15 minutes to 2 hours after the last intake of milk or dairy products. The severity and appearance of symptoms depend also on the amount of lactose consumed.

The disease can be recognized by its characteristic signs and the patient history. Of course, only a thorough physical exam can lead to a precise diagnosis. This disease may pose some diagnostic difficulties if the symptoms appear after a longer symptom-free period that follows the ingestion of milk; in such cases, neither the patient himself nor his/her physician link the symptoms to the inability to metabolize milk. The diagnosis can be made by excluding all milk products from the patient's diet. If after excluding all milk products the symptoms disappear, no further diagnostic procedure is necessary. In order to unequivocally confirm the diagnosis, the so called lactose tolerance test may be performed: the patient consumes 50g of lactose and the body's reaction to it is studied.

Lactose intolerance forms

The incidence of lactose intolerance varies greatly among different ethnic groups. The disease affects about 15% of Caucasians in the USA and Europe. There are no differences between the sexes. In Japanese and Chinese populations, the disease affects about 80% of the people, while in certain South American peoples, especially the indigenous people, virtually all people are affected.

The disease can be subdivided into primary (genetic) and secondary form. Primary lactose intolerance appears most often in childhood. The enzyme amount at the time of birth suffices for the infant's normal development; after the age of 2 or 3, however, the first signs of milk sugar malabsorption become evident.

Secondary lactose intolerance is characterized by a normal amount of digestive enzymes for lactose; however, the intestinal mucosa is injured due to the effects of other diseases and it prevents normal absorption and digestion of lactose. Diseases that are most often accompanied by the secondary lactose intolerance include the chronic inflammatory bowel diseases such as Crohn’s disease; celiac disease, post-irradiation disorders as well as post-chemotherapy (cancer therapy) lactose intolerance.

Treatment of lactose intolerance

The treatment for primary and secondary lactose intolerance is following a diet that is low in milk content or entirely milk-free. In the case of secondary lactose intolerance, the primary disease is treated concurrently, if at all possible.