What is the origin of lactose intolerance?

What is the origin of lactose intolerance?

It manifests itself with the coeliac condition, but it has different causes.

Before and after their coaliac condition is diagnosed, coeliacs may also present with an intolerance to lactose caused by the presence of a diffuse lesion of the intestinal lining. Nevertheless, a reduced tolerance to lactose may persist even after the beginning of the treatment of the coeliac condition, when the structure of the intestinal lining has already normalised. This situation is caused by a lack of enzymes that is genetically based. This is very frequent in the general population, especially in the countries of southern Europe, and has nothing to do with the coeliac condition itself. In these cases, the consumption of foods which are rich in lactose, especially whole cow's milk, may cause persistent symptoms such as abdominal pain and flatulence. The treatment of this condition requires the avoidance of foods that are rich in lactose, such as whole milk and dairy-based ice cream. In place of whole milk, it is advisable to consume products low in lactose, which are nowadays available in all supermarkets. Since the intestine retains the capacity to digest limited quantities of lactose, other dairy products such as yoghurt, cheeses and milk biscuits are generally well tolerated in less severe cases.