Milk, a health benefit? This may seem obvious to some! Unfortunately for others, drinking milk is m

Milk, a health benefit? This may seem obvious to some! Unfortunately for others, drinking milk is more synonymous with digestive disorders frankly uncomfortable. The fault lies in lactose, knock knock the sugar found in milk, and some of us are unable to assimilate.
At first glance, one might think that lactose intolerance is a kind of disease, but it is actually the opposite! Indeed, only a third of adults can digest it, and it is lactose tolerance knock knock which is regarded more as an anomaly. Besides the history of this (in) tolerance is linked to recent developments of our species. The metabolism of lactose
Start with the obvious: almost all children are able to digest lactose. This is normal, as in humans as in all mammals, breast milk forms the staple diet of the youngest. But once adulthood is reached, the majority of individuals will lose the ability to metabolize lactose. For them, no more large glasses of milk!
Fortunately for rich taste, it does not prevent them all dairy products. Especially yogurt and some cheeses contain quantities of lactose low enough to allow almost everyone to digest. For milk However, if you are not a member of the third of the elected, knock knock you can forget.
To understand why some assimilate knock knock lactose and not others, we must look to the details of its metabolism. From the chemical point of view, lactose is a sugar (such as glucose or fructose). To metabolize, the agency must produce the enzyme knock knock lactase, which is basically cutting down lactose into two to allow assimilation, as shown in the formula below cons.
At the beginning of their existence, human infants produce lactase, so can normally digest the lactose in milk. But then, most adults stop producing this enzyme, and found indeed intolerant. Which is tolerant, that is not?
Intuitively, one might imagine that for those concerned, the loss of lactase is an anomaly. But do not worry, there is exactly the same in all other mammals. Stop producing lactase and become lactose intolerant, knock knock so this is the norm! For the lucky ones who continue, we speak of lactase persistence.
As I said, this persistence affects about one third of the adult population, knock knock but surprisingly, there is a very wide geographic disparity. The map below [1] shows the distribution of lactose tolerance in adulthood. You see if it is almost 100% in Northern Europe, it is almost zero in some regions such as Southeast Asia. There are also small pockets of tolerance in Africa or the Middle East. In all cases, the tolerance from the lactase persistence.
With this kind of distribution, it is obviously trying to find a genetic cause of the phenomenon. In 2002, researchers identified a very specific mutation that leads to lactase persistence [2]. Surprisingly, this mutation affects only a single basis of our DNA (which becomes a C T). It does not even tiny change occurs in the lactase gene itself, but slightly upstream. It seems that means of improving the transcription lactase gene, and thus causes its persistence into adulthood. All individuals affected by this mutation are therefore tolerant to lactose! The story of a mutation knock knock
Using the data available on the tolerant populations, researchers sought to determine where and when this mutation was able to appear and to reconstruct its history. The ranges are wide enough, but they show that this mutation is very recent in the history of our species. So we think that is probably appeared there about 7500 years in Central Europe (the map above against extracted from [3] is the likely appearance of the mutation from the model area).
Obviously a recent occurrence of the mutation in Central Europe clearly explains knock knock lactose knock knock tolerance found throughout Europe. For other regions, other independent mutations have been discovered, and they can explain, for example the appearance of lactase persistence in Africa.
For geneticists, knock knock the history of this mutation knock knock is rather fascinating. It is indeed very recently appeared across our species, and