Lactase deficiency (LCT polymorphism)

Why this test?

In case of of lactose intolerance symptoms (intestinal bloating, intestinal disorders, nausea, etc. ) after consuming dairy products.

Differential diagnosis of lactose intolerance and other diseases of the gastrointestinal tract in adults.

To assess the probability of lactose intolerance in children older than 1.5 years and adults.

In what cases is it prescribed?

With symptoms of lactose intolerance (intestinal bloating, defecation disorders, nausea, etc. ). In the differential diagnosis of lactose intolerance and other diseases of the gastrointestinal tract in adults.

To determine the probability of osteoporosis developing.

To assess the likelihood of lactose intolerance in young children, to prevent intestinal disorders.

Test information

Lactase deficiency, or lactase insufficiency (lactose malabsorption, hypolactasia), is a violation of lactose breakdown due to lactase deficiency of the mucous membrane of the small intestine, which is accompanied by clinical symptoms. Lactose (milk sugar) is found only in the milk of mammals and humans. It promotes the absorption of calcium and other minerals in the intestines, as well as the reproduction of lactic acid bacteria beneficial for the body. Lactose is used in the manufacture of many food products, mainly dairy products; the pharmaceutical industry also uses lactose as an excipient. The action of lactase (an enzyme produced in the small intestine) is necessary for the assimilation of lactose. The body's ability to break down lactose depends on the amount of lactase and its activity, which is manifested from the 12-14th week of intrauterine development, reaching maximum values by the time of birth (at 39-40 weeks). After birth, a child with a normal genotype has a decrease in enzyme activity at 6-11 months and later up to 2-5 years - this is called primary, or age-related, lactase deficiency. It is caused by a hereditary deficiency of the lactase enzyme and is inherited in an autosomal recessive manner. The consumption of whole milk and other products containing lactose in this case leads to digestive disorders: bloating, pain, flatulence, diarrhea. Individual symptoms of lactase deficiency are different, and their severity may depend on the state of the intestinal microflora, nutritional characteristics, and psychological factors.

Prevention consists in preventing the symptoms of hypolactasia by following a diet with a low lactose content or its complete absence. Therefore, with symptoms of indigestion after consuming unfermented dairy products, it is advisable to conduct a genetic test for lactase activity in order to avoid attempts at meaningless treatment and to choose an appropriate diet. Also, the test has prognostic value in terms of the development of lactose intolerance in children in order to prevent unexpected intestinal disorders.

It is important to remember that avoiding milk and dairy products, which are an important source of calcium, can lead to calcium deficiency, which increases the risk of osteoporosis (especially in postmenopausal women).

Primary lactase deficiency should be distinguished from secondary (acquired), which occurs when the mucous membrane of the small intestine is damaged against the background of any acute or chronic disease. Such damage is possible with infectious (intestinal infection), immune (cow's milk protein intolerance), inflammatory process in the intestine, atrophic changes (with celiac disease, after a long period of full parenteral nutrition, etc.).

The study is not related to a rare genetic disorder - congenital lactase deficiency, the symptoms of which appear immediately after birth and are associated with the start of breastfeeding.

Lactase deficiency is caused by a decrease in the transcription of the LCT gene, which encodes the enzyme. The MSM6 gene is located in close proximity to the LCT gene, which affects the expression of the lactase gene. It has been proven that replacing cytosine (C) with thymine (T) in the 13th intron of the MSM6 gene increases the expression of the lactase gene. Carriers of the main C allele are characterized by a decrease in the level of lactase in adulthood, that is, lactase deficiency. Carriers of the minor T allele, on the contrary, can assimilate lactose, and this ability is not lost over time.

Lactose intolerance is most common in North America, Africa, and Southeast Asia (the birth rate of the C allele reaches 100%, compared to approximately 48% in Europe).

Information about the genotype of the C (-13,910) T marker of the MSM6 gene will help the doctor choose a diet with low lactose content or its absence for adult patients, prevent digestive disorders in children, and assess the risk of developing osteoporosis in women during menopause.