The post identified is somewhat ironic. That information is from a member who was banned from those particular forums. The guy does not appear to be a recognized expert & I have detected some flaws in the information that he has provided.
It is probably true for many, but not most, people that lactase production is diminished or halted after early childhood. This is true for many Asian people, particularly those who stop drinking milk after the age of 2 or 3. On the other hand, many adults still produce enough lactase to digest milk protein. The levels or lactase & renin may decline somewhat as we age but, except for lactose-intolerant individuals, the levels are still high enough to digest some milk protein.
The poster identifies casein as an "element in milk" but fails to identify casein as a protein. It makes up nearly 80% of the protein in cow's milk whereas whey protein accounts for about 20%. Note that whey protein is rather unique in that it is assimilated by our body very rapidly. Most other protein takes hours to digest & assimilate. This is true of milk (casein) protein and egg protein. Some sources suggest that it is best to include protein that is assimilated quickly, whey, as well as protein that provide a more sustained source of amino acids, such as egg or milk proteins.
