The reason is mainly that Asians lack an enzyme, namely lactase.Lactase is needed to break down the milk sugar lactose into its digestible substances. Infants produce this enzyme in order to be able to utilize their mother’s milk. If it is missing, the milk sugar begins to ferment in the large intestine. This leads to symptoms such as flatulence, colic, and diarrhea. However, Asians are not the only ones who “suffer” from this deficiency, as most adult mammals – including humans – do not normally tolerate milk.
Northern and central Europeans as an exception
But why is it that most northern and central Europeans are an exception? The reason is as simple as it is comprehensible in terms of developmental history: as long as mankind did not know dairy farming, adults did not enjoy milk. As a result, they lost the ability to produce lactase after infancy.
However, this only had consequences when, around 12,000 years ago, people in the Near East began to tame animals and drink their milk. They noticed that they could not tolerate fresh animal milk. But they also did not depend on milk as a source of calcium. This was for three reasons:
- They had sufficient green leafy vegetables to consume
- They consumed enough sea fish and thus enough vitamin D
- They took in enough sunlight, which ensures that the body can produce vitamin D
The situation was different in northern Europe, where dairy farming gradually spread. But there was neither enough green leafy vegetables available, nor was the sunlight sufficient for the formation of vitamin D. Milk was therefore used as a source of calcium.
Genetically, the northern Europeans, who could drink and digest the milk of their animals, then prevailed and successfully reproduced.