Beneficial though not essential, it is very common that adults do not feel at all well to drink milk, although not all of us feel bad in the same way: some may be lactose intolerant while others may be allergic to protein. cow’s milk. Let’s see what the difference is.

Allergy to cow’s milk protein

This case is that, an allergy . That means that it is the immune system that is involved : by detecting an agent that is considered harmful to the body, it overreacts by triggering what we call an allergic reaction. Spiciness, redness, swelling, vomiting. The respiratory system can be affected, as well as the skin and eyes.

The culprit is the protein present in cow’s milk, but often this allergy also extends to sheep’s milk or goat’s milk.

To diagnose it, a blood test is done to measure the levels of immunoglobulin E (IgE), an antibody involved in the immune response to external agents and parasites. Those affected by this allergy try to avoid consuming any dairy product.

Lactose intolerance

Here we no longer talk about allergy but intolerance , and that means that things change. Nothing here paints the immune system, which gives all the prominence to the digestive system .

In lactose intolerance is key lactase , an enzyme that produces the small intestine and is responsible for processing lactose, milk sugar. When it is not produced, or not enough is produced, the lactose passes into the large intestine and there generates swelling, pain, fatigue, bloating, diarrhea and flatulence.

The advantage of this pathology against the allergy to cow’s milk protein is that there are currently many lactose-free dairy products (beneficial for intolerant but equal for all others ), so that for the intolerant it is not necessary to eliminate the milk and its derivatives totally from your diet.

Lactose, lactase and evolution

The case of lactose intolerance is very interesting when it comes to understanding how the human being evolves. If we stop to think, it would have a certain logic that adults could not digest milk properly, right? After all, no adult mammal drinks milk. Milk is a food that only the young consume .

According to one study, the vast majority of people in Neolithic Europe lacked the genetic traits needed to properly process lactose

In fact, thousands of years ago it was also like that among human beings. According to one study , the vast majority of people in Neolithic Europe lacked the genetic traits necessary to properly process lactose. Infants and younger children produced lactase without problem, but that production was off after a few years.

And yet to this day, although still a minority, tolerance to lactose is common , especially in people of European descent.

How do we go from one thing to the other? Why do we develop and extend the ability to process milk, beyond childhood ?

The answer is not clear at all, but it seems that at some point, drinking milk proved to be an advantage . This is not surprising: milk is rich in nutrients such as proteins, carbohydrates and essential minerals such as calcium. For our ancestors, it was a superfood.

Even if the lactose did not sit well with them, the benefits outweighed the drawbacks. Remains found in millenary settlements show that they learned to manipulate milk to make yogurt and cheese, which eliminated part of the lactose in the milk .

According to some research, about 8,000 years ago in the region of Turkey appeared a genetic mutation that affects the production of lactase, maintaining it throughout adult life. The mutation was spreading throughout what is now Europe.

The advantage of being able to drink milk

According to Mark Thomas , an expert in evolutionary genetics at University College London, this rapid and successful expansion, especially in northern Europe, was due to two reasons.

The combination of both factors resulted in a greater mortality of all those who could not tolerate and assimilate lactose, as well as a higher probability of survival for those who could.

The first is that the farmers who settled in these regions came from the so-called Fertile Crescent, the historical zone that includes the Mediterranean Levant and the ancient Mesopotamia and Persia. From there they took their wheat and barley crops . But in a colder environment and more abrupt seasons, these did not always go ahead, causing major famines .

The second is that the climate of these regions, cooler, was much more conducive to the preservation of food, such as milk , which would take much longer to curdle in yoghurt (thus losing part of the lactose), than in its places of origin, warmer.

If a healthy person with lactose intolerance consumed high milk lactose, he suffered a severe case of diarrhea, but if the person was also severely malnourished due to lack of food, the chances of him dying were much higher.

The combination of both factors resulted in a greater mortality of all those who were not able to tolerate and assimilate lactose, as well as a greater probability of survival for those who could. The theory of Thomas, still to be confirmed, postulates that although tolerance to lactose is not a great long-term evolutionary advantage , it could be at specific times of bad harvests and famines by allowing a group of people to take advantage of a rich source of nutrients that for others supposed a serious health problem.