Milk and its products contain estrogen. Extra estrogen in your body causes micro inflamations. Extra is anything you did not produce yourself.

There may be many other effects of milk that we do not know, but fact is that it works for super rapidly growing bodies such as babies. So it cannot be good for aging bodies such as adults. It might be medicine if used only once or twice in a lifetime to help kick the body to cure a speciffic illness, but if used often, it is drug abuse as any other.

Also, it is immoral and unnatural. Animals are enslaved and their organs abused to steal their milk. Natural way of getting food is not enslaving any animal. Natural is when every creature lives free, and you only kill individual ones after they lived a free life. The same as with plants. They live free, but some you kill to eat. Or you steal and eat eggs. Just like you steal and eat fruits before they become a new plant.