The main priority when choosing natural dairy products is the percentage of fat and personal taste preferences. But try not to "fix" on one product, try all the abundance and variety presented (yogurt, kefir, cottage cheese, milk), try to give preference to low-fat, natural products. When choosing dairy products, give preference to those whose fat content does not exceed 5%. For example, for breakfast - cottage cheese, for an afternoon snack - yogurt, and in the evening a glass of milk or kefir.
When making milk, its population with lactic acid bacteria is taken into account and, in order to protect it from souring, it is sterilized according to the Pasteur method: it is sharply heated to + 60-65 degrees, and then it is also sharply cooled to + 4-5, causing temperature shock and death many bacteria. Many, but not all, because the spore-forming ones survive at the same time - they don't care about anything in their disputes.
Thus, at the output we get a set of proteins, fats, carbohydrates; maybe some vitamins. At the same time, there are no lactic acid bacteria, so you will have to assimilate this lactose with the help of your own, which is in the intestines. It is harder, so many adults develop milk intolerance over time - lactose is absorbed very poorly.
Fermented milk products are another matter - they are full of bacteria, and they are mainly beneficial bacteria that will establish microflora inside and even allow strengthen immunity. Mechnikov at one time actively promoted the benefits of his famous yogurt, justifying this precisely by the beneficial effect of lactic acid bacteria on human health. Indeed, if you have a healthy microflora, then any antigens that enter the body can be eliminated with much greater efficiency than with dysbiosis.
In short, my answer: sour milk is definitely more useful, and it is absorbed better
Here, depending on what products to buy, if with regards to milk, then you need to take pasteurized, it contains more vitamins, because milk is heated to 60-70 degrees. And sterilized at 115-135 degrees, at this temperature, all useful properties are lost.
If we are talking about kefir, then you need to take kefir with a shelf life of no more than one week. I would say that both products have their benefits, and it is difficult to choose a leader, another question is what products you buy, and whether they really have a sufficient amount of vitamins. Now on store shelves most of the dairy products are dummies.
Live yogurt has a shelf life of no more than 6-7 days and should be stored exclusively in the refrigerator at a maximum temperature of 7 degrees. If the packaging indicates a one-month shelf life, such yogurt is absolutely useless - the bacteria in it are dead, but there are many preservatives. Moreover, sugar is often replaced with artificial sweeteners such as aspartame to reduce the cost of yogurt. Undoubtedly, the presence of harmful compounds in fruit yogurt is minimal, but their very presence turns this product into a dummy.
Kefir has a beneficial effect on the intestinal flora, which protects us from many diseases, promotes its reproduction and health. Kefir helps a lot with dysbacteriosis, loss of strength, weakened immunity and anemia, has a positive effect on chronic fatigue syndrome, neurotic diseases and sleep disorders. Kefir is useful for everyone, but it is especially recommended for children, the elderly, and those who are recovering from an illness.
Many people use a kefir diet to lose weight. Of course, this is also an option, but it is better to drink kefir always. If kefir occupies a permanent place in your diet, you are unlikely to suffer from excess weight.
Now about milk. Fresh and fresh milk has excellent bactericidal properties and contains more than a hundred medicinal components. To preserve these properties, fresh milk is cooled, but they still do not last more than a day. Fresh milk can help neutralize radiation, toxic substances, heavy metal salts. That is why he is given out to workers in "harmful" industries. In diets, fresh milk is used because all the substances in it are in an easily digestible form. Morning milk is easier to digest than evening milk because less time passes between milkings and therefore less fat is formed in morning milk.
Kefir definitely wins out of three products in terms of availability for urban residents. But if you make homemade healthy yogurt, and have the opportunity to drink fresh morning village milk, then this is only a plus.
I assume that milk with kefir. First, yoghurts are generally not very healthy. Yes, it is a dairy product, but mainly from carbohydrates, and not, as it should be dairy, from protein.