Lactose intolerance is transient when the inability to properly digest the sugar contained in milk is not genetic, that is, it does not depend on the fact that the organism is not able to produce enough lactase enzymes – explains Dr. Beatrice Salvioli, gastroenterologist at Humanitas. In cases where there is no lactase – a rarer form that usually occurs from the weaning period onwards – symptoms already occur when the infant is fed breast milk. In all other cases, however, lactose intolerance is acquired or secondary, and it can arise at any age for various reasons as a result of disease, inflammation of the intestines or antibiotic therapies that inhibit the activity of the lactase enzyme. In these cases lactose intolerance is transient, i.e. the sources of lactose can be gradually reintroduced into the diet after a 3-6 month elimination period. The most common diagnostic test for possible lactose malabsorption (and therefore the absence of the enzyme) is the breath test, a non-invasive test that consists of the analysis of the air exhaled by the subject before and after the administration of a dose of lactose. When the milk sugar is not digested and starts to ferment, there is an overproduction of hydrogen that the test detects if there is malabsorption. A genetic test on blood, on the other hand, can detect the possible persistence of the lactase enzyme.
