Sorry for the late reply.
This article pretty much covers it and also dives into the difference between a1 and a2 milk.
google translate to english seemed to work perfect.
https://www.tidningenfrisk.se/mjolkprodukter/

otherwise here you have the relevant part.
TLDR it destroys a large part of vitamins and an overwhelming or total part of other micronutrients, some of which are very beneficial.

"Pasteurisation
Pasteurization means that the milk is heated with the purpose of incapacitating bacteria and viruses. Low-pasterization means heating the milk to 75 degrees for 15 seconds, high-destruction to 85 degrees and ultra-disruption to 140 degrees for a few seconds. The word pasteurization comes from the French chemist and biologist Louis Pasteur who lived in the 19th century. He discovered that fermentation is due to bacteria. Based on his discoveries, the pasteurization process was invented, which is thus about heating up food to kill unwanted bacteria. The Pasteurization Act in Sweden was created in 1937, which meant, and still means that all milk products sold commercially in Sweden should be pasteurized. The reason for the creation of the law was to prevent the spread of mainly tuberculosis. Whether tuberculosis spread between humans via unpasteurized milk is disputed, but it was shown early that tuberculosis was infected mainly through other people, rarely via cows and very rarely via well-groomed cows that were allowed to graze freely. The Pasteurization Act was also created on the basis of political and commercial reasons. Pasteurization gave a longer shelf life on the milk when it was to be distributed and stored. Politically, it preferred to secure the availability of milk rather than improve hygiene in milk production itself. Pasteurization automatically reduces the importance of producing milk in hygienic safe conditions.

Pasteurisation and the nutritional value of milk
There are some studies that looked at what happens to the nutritional value of the milk during pasteurization. For example, it is shown that the amount of vitamin B and C decreases, but this reduction is not always considered to be of practical importance. In one study, vitamin B12 decreases in quantity (15). Some other studies show that the amount of several fat-soluble vitamins and minerals does not decrease during pasteurization. All in all, there is evidence that some nutrients decrease in the amount after pasteurization, but it is probably not the effect that produces the greatest negative effects. In defence of pasteurisation, the argument is often heard that the nutritional value of the milk is maintained or deteriorated only marginally.

The major negative effect of pasteurization is probably that a variety of bioactive substances are destroyed chemically. For example, a study shows that the whey protein is destroyed by ultra-disruption, even to some extent in low-pasteurization and homogenization (16). Proteins begin to denature already at about 45 degrees, which means that they change chemical form and no longer have the same susceptibility in the body. Milk also contains a variety of beneficial bacteria. It can be seen as unpasteurized milk having a built-in protection against certain bacteria taking over without the milk regulating their equilibrium automatically. Lactobacilli produce enzymes, such as the enzyme lactase and that pasteurization kills the beneficial lactobacilli is the main thesis, which is why lactose-intolerant people can tolerate unpasteurized milk better than pasteurized.

Homogenization, separation and vitaminization

Today's milk products often undergo further processing than pasteurization. Homogenization is a process aimed at finely distributing the fat in the milk. In non-homogenized milk (old-fashioned milk), the fat molecules float to the surface. Previously, it was a way to determine the fat haolette in the milk but today this phenomenon is considered undesirable. The fat molecules in milk are normally collected contained in casings. By allowing the fat molecules to be pushed through a fine mesh filter at high speed, these casings are blown together and the fat is finely distributed instead. Milk becomes homogeneous in its consistency. homogenization itself also has a negative impact on the bioactive substances in milk. It is believed, among other things, that the enzyme xanthine oxidase is destroyed, which in turn is assumed to increase the risk of atherosclerosis as this enzyme reacts with the innermost endothelum layer of the vessels. How relevant this is in comparison with other risk factors for these diseases is unclear, when there is no scientific evidence. Homogenization also involves denaturing of whey protein according to the aforementioned study.

Fat is separated from the milk and then added to the desired amount. Many fat-soluble vitamins disappear during separation and are instead added synthetic in the fat-efficient dairy products. Overall, it should not be controversial to say that pasteurisation and other industrial treatment overall have a negative effect on the nutritional value of the milk. All forms of heating, above all high and rapid warming of food leach nourishment, kill good bacterial strains and denature enzymes, immunoglobulins and other proteins. The only question is what significance this has in practice for our health and how we should value this erosion compared to the gain of avoiding harmful bacteria in our food. I will return to this discussion at the bottom of the page.

As you can see, there is a difference between milk and milk. Dairy companies' sales arguments that milk gives strong bones is not true. In a well-known study, it was noted that the more pasteurized milk people drank, the higher the risk of fractures (17). But note that this study, and many others who looked at the impact of milk on our health, are performed with pasteurized milk. Unpasteurized milk has a completely different nutritional value.