Should we drink cow's milk (or from any other animal)?

At birth all mammals have the enzyme lactase. This enzyme is essential to digest lactose, which is, to put it simply,  the sugar of the milk. If we did not have the lactase enzyme, the digestion of dairy products would be very complicated, if not impossible: we would suffer intestinal pain, gas and in extreme cases fever and general malaise. Including death. In ancient times, newborns who completely lacked the lactase enzyme were hopelessly doomed. They couldn't be breast feed (human milk has lactase) and neither take any other kind of milk.

Most mammals lose the ability to synthesize the lactase enzyme within a few months or years of life. From that moment on, since it no longer receives the mother's milk, it is not necessary to continue synthesizing the lactase enzyme. Three-quarters of the world's human population follows this pattern. Many populations in Africa, Asia and America cannot consume milk or dairy products, becoming severely ill if they do.

Europeans underwent a mutation around 6,000 BC, probably in an area north of the Balkans, which allowed them to synthesize the enzyme lactase in adulthood, making it possible for them to feed on milk regardless of their age. This evolutionary change was positive in those areas where access to certain vitamins and calcium through fruit and vegetables was not easy. In others, especially southern Europe, it was not so decisive and in fact, if southern Europeans can consume milk, it is more due to the genetic contribution of the emigration of Central European populations than to a nutritional need.

The consumption of dairy products in humans, even those who can, is not without some controversy.

Some believe that the milk that humans should consume out of obligation and exclusively, except in cases of severe lactase enzyme deficiency, would be from the mother. Human breast milk is the only one that has the appropriate composition for humans, just as the mare naturally produces the perfect milk for the foal. Changing the 'natural source of milk' can have long-term adverse effects. Thus, for example, cows produce a kind of morphine within milk to calm their calves and allow them to take the daily ration with ease. This same substance reaches humans when they consume cow's milk, producing relaxation. That is the reason why some people drink a glass of hot milk before going to sleep - without which they are not able to sleep - and it also explains the reason people are very addicted to cheese consumption where the concentration of this substance is much higher than in milk. 

Another argument against the consumption of milk is to indicate that it is designed for the growth and fattening of calves, not of human beings and less of adult humans. Therefore, it contains amounts of fats that are not very suitable for adults. This is easy to solve by taking skimmed versions of milk but there are other substances from which it is not so easy to escape. Cow's milk contains hormones that have their reason for being in calf growth, but have possible adverse effects on humans. For example, some argue that these hormones have a high impact on various diseases, such as cancer that has a hormonal origin (breast, ovarian, prostate cancer, etc.). Some people have experienced improvements in their hormonal cancer, and have even resolved completely, eliminating dairy from their diet.

Even among humans genetically presumed to have the lactase enzyme, milk is often problematic. From the age of 25, the synthesis of this enzyme decreases and lactose intolerance may appear, even at very advanced ages, although until that moment milk was digested without problems. It also occurs during childhood and, as mentioned above, some are born with a total lack of this enzyme (which would have been a fatal problem years ago, whereas nowadays substitutes can be prepared without problems).

Having lactose intolerance would not be a big problem. As we have said, billions of human beings lack it and they look so happy. They get their vitamins and calcium from other foods and they do not have nutritional deficiencies. Milk is therefore an expendable food. If this mutation occurred thousands of years ago, it was because in those populations north of the Balkans the economy was predominantly livestock and feeding on a by-product such as the milk that cows gave to their calves was an evolutionary advantage.

The problem, especially in the West, is twofold: on the one hand, an infinite number of products contain milk, many of them unthinkable. All milk protein cleanse of dairy would be a daunting task. On the other hand, we have a very powerful industry that constantly creates new foods where milk is an essential ingredient. Fighting against this industry is another task even more than titanic.

So lactose intolerant people have a very difficult time. Either they go to live in the Far East or they try to adapt as best as possible to the circumstances. Those who are intolerant have lactose-free milk or can consume similar substances of plant origin. When they buy any food they should read the ingredients carefully and if they go to a restaurant they can take some pills that incorporate the enzyme lactase and which will mitigate the adverse effects of unexpected dairy ingredients. In any case, being lactose intolerant it's a problem dependening where do you live.

If we do not have problems with the lactase enzyme we can drink milk whenever we want, but my advice is to reduce its consumption drastically beyond the age of 25. All the nutrients in milk can be easily obtained from other foods and even one as praised as calcium is present in sufficient quantities in green leafy vegetables. A salad a day is equivalent to several glasses of milk, without the danger of gaining weight or taking substances that in the long run can represent problems for our health.