Most dairy products contain lactose, a sugar made up of two molecules (glucose and galactose). In order for the body to digest it, these elements must be separated by an enzyme: the lactase. Infants make a lot of it during the first months, but the amount of lactase produced by the body declines over the years and makes the digestion of lactose difficult or even painful.
If lactose is not cut by this enzyme, it cannot be absorbed in the small intestine. It will therefore continue its way through the digestive tract and arrive in the colon where the intestinal bacteria will ferment it, which will create a gas production and one water call. “It is rare for a person to produce no lactase at all. But when lactase secretion capacities are exceeded in relation to the quantity of lactose absorbed, there is malabsorption. “, explains dietitian Raphaël Gruman.
What are the signs of lactose intolerance?
If the lactose passes the small intestine without being – or not completely – absorbed, it then reaches the colon, where it will ferment due to the specific intestinal flora of this section of the intestine. This results in bloating, pains, diarrhea Or vomiting for the most serious cases. The appearance of these symptoms after ingestion of milk generally leads to the suspicion of lactose intolerance. However, this can be confused with a milk protein allergy. But several tests can confirm an intolerance.
“I sometimes prescribe an intolerance test by blood test (not refunded) to my patients, the results are quite reliable “, says the dietitian. The doctor for his part can prescribe a respiratory test which is carried out in the hospital: the level of hydrogen exhaled before and after absorption of lactose is measured, the undigested lactose being transformed into gas (including hydrogen) under the action of intestinal bacteria. The digestive signs being common to other pathologies (celiac disease, irritable bowel syndrome, Crohn’s disease…), it is important to make a good diagnosis.
Can lactose intolerance be treated?
Once the diagnosis is made, the health professional will prescribe a strict diet for a month. “TAll foods that may contain lactose, including cheeses, ready meals or industrial pastries will be prohibited, to suppress symptomssays Nicolas Mathieu, gastroenterologist at the Grenoble University Hospital. After a month, we will try to reintroduce foods where there are traces of lactose: dry cheeses, biscuits, etc. And we continue the reintroduction to find the tolerance threshold, so that the patient can have the most varied diet possible. “.
Nicolas Mathieu does not however recommend a lactose-free diet except in cases of intolerance. A deficiency in calcium would risk causing decalcifications, of the osteoporosisand therefore broken bones. “In addition, we do not yet know the consequences that a lactose-free diet can have on the gut microbiotadevelops Doctor Mathieu. However, if we modify the richness or the variety of this flora, it seems that we promote certain diseases such as diabetes. Such a modification can induce in some patients too violent interactions with the proteins of the intestine, and lead to a chronic inflammatory bowel disease. (MICI).”
To know : hard cheeses (which contain only traces of lactose) are usually not a problem. No more than yoghurts, which contain lactic ferments which “pre-digest” lactose, in other words which play the role of lactase deficiency. Finally,“dairy products are generally better digested when they are cooked and incorporated into a recipe, such as milk in a cake or cream in a gratin”, says Raphaël Gruman.
Intolerance or allergy: how to tell them apart?
An allergy is triggered by a protein, not a carbohydrate like lactose. It is an abnormal reaction of the immune system, with production of antibodies (IgE) and release of histamine and other substances responsible for the allergic reaction (itching, swelling). An allergy can have serious consequences (asthma, edema, anaphylactic shock) while lactose intolerance, although it causes unpleasant symptoms, is not serious. An allergy requires the total exclusion of foods containing the allergen (problem protein), while in the case of lactose intolerance, small amounts are often tolerated. Everyone must determine their own tolerance level.
To note : Cow’s milk protein allergy is quite common in toddlers (2 to 3%), but disappears in 80% of cases around the age of 2 years.
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