Why do some people digest milk badly?
What can be a problem in milk is its sugar, lactose: it contains about 5%, compared to 3 to 4% for yogurts, fresh cream or ice cream. To properly digest this sugar, our body must be able to manufacture the corresponding enzyme, lactase. But without its manufacturing instructions, in other words without its gene, our cells are quite incapable of producing it. However, since the distant time when we began to take advantage of the milk of cows, goats and sheep, around 10,000 years ago, this gene has been transformed.
Thus, in Asia and the Far East, today only 10% of men and women have the correct version of the gene: the one which, thanks to a small mutation, makes it possible to digest lactose from efficient way. In this region of the world, 90% of people are therefore lactose intolerant. For them, milk inevitably triggers diarrhea. This is not the case in the countries around the Mediterranean, where one in two people has the right lactase. And in central and northern Europe, where dairy products have always been important, almost everyone is well equipped!
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Various causes of intolerance
In France, intolerance therefore remains exceptional. But that does not mean that we all digest milk perfectly. In addition to the tiny percentage of people who do not have the right lactase, other people have a hereditary abnormality: the lactose passes through the lining of their stomach and, once in the blood, this sugar can poison the body. .
Another concern, the most common cause of intolerance in newborns: certain diseases weaken the lining of the intestine and thus interfere with the digestion of milk. It can be an infection with viruses, bacteria or parasites, an inflammatory disease, allergies, reactions to medications, etc. The problems disappear as soon as the disease is cured.
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A more difficult digestion with age
The fact remains that in mammals such as we are, the lactase enzyme becomes less active upon leaving childhood. In adolescence or adulthood, this efficiency can decrease by 90%, resulting in difficulties in digesting lactose. But this sensitivity varies in its symptoms, from person to person. Some suffer from bloating and diarrhea as soon as they swallow a small glass of milk, others only react after consuming too much.
In addition, the sensitivity is more or less strong depending on the dairy products: skimmed milk is less well tolerated than whole milk, to which we are generally more sensitive than to milk preparations, which cross the stomach less quickly . Let's add that yogurts have bacteria on their side that predigest lactose. And that mature cheeses have very little lactose, draining having eliminated some of it, and the bacteria the rest.
Finally, as Francis Raul, research director at Inserm, points out, “the presence of other foods reduces or eliminates any difficulty in absorbing lactose”. For those in whom dairy products are really a source of inconvenience, it is better to avoid consuming them on an empty stomach. Without depriving yourself of it, because they are useful sources of calcium. Although, fortunately, nature does things well: by a compensation mechanism, those who consume less calcium are able to absorb it more efficiently.
