From various sources:
There are two sources of vitamin D, it is made in the skin by exposure to sunlight and there are a few dietary sources, such as oily fish, eggs, and fortified foods including margarine (which is required by law to contain vitamin D), some yogurts and breakfast cereals. There is very little vitamin D in milk and in fact only trace amounts and in the UK milk is not fortified with vitamin D.
Milk contains all the vitamins required by mammals. The fat soluble vitamins, A, D, E, and K, are found primarily in the milk fat; milk has limited amounts of vitamin K. The B vitamins are found in the aqueous phase of milk. Fluid milk in the US is fortified with additional vitamin D. Vitamin A is also added to milk in some other countries.
Vitamins are essential organic compounds required in the diet. Most are not synthesized in the animal (there is some synthesis by the microflora in the intestine). Therefore, milk levels can be influenced by dietary levels. Milk contains all of the B vitamins and fat-soluble vitamins, except perhaps vitamin K.
The fat soluble vitamins (A, D, E, K) are associated with the milk fat globule.
Vitamin A : retinol : Yellow milk fat of Guernsey cows is due to lower efficiency of conversion of ß-carotene to retinol. In some countries milk is fortified with vitamin A.
Vitamin D : antirachitic activity : Involved in bone metabolism, Ca absorption in the intestine, and has other tissue functions. Milk is often fortified with vitamin D.
Vitamin E : tocopherol : Antioxidant, protects lipids. Only low levels are present in milk.
Milk is supplemented with an artificial version of Vitamin D which acts differently. It binds Magnesium, which results in acid reflux. And you all know how much $$$ the pharma makes from acid reflux. The MDs don’t want you on the real thing.