But, even if you are right -- the nutritional problems of the caveman were not the nutritional problems we face today:
Today the problems mostly deal with chronic diseases that occur in later life. The cave man imply didn't have a later life.
... the evolutionary argument -- even if true is simply not relevant.
Frankly, I don't care if my system adapted to let me eat insects -- I prefer to get protein from plant sources.
And, even if it adapted to let me digest red meat -- with my family history or heart disease it would be foolish for me to indulge in a BigMac.
Because you CAN is not a persuasive argument that you SHOULD.