Although it can be nutritionally appropriate, it may still not be good for the body. I am not a biologist, but I don't believe that the body is built for finely processed food. I am assuming that there is some research correlating highly processed/refined foods and the some of the common ailments in the western world.
A great example I have seen showing processed vs non-processed foods is to simply put the food in a bowl of water. A lot of processed food will within a matter of minutes puff up to a multiple of their size, and when stirred will simply break up into a liquid solution. Natural (unprocessed, even minimally processed) foods will generally stay together for a lot longer.
Give it a couple of centuries, and we'll see how the human gut and digestive system evolve. Oh wait, we'll have medical systems to prevent natural selection, so we're going to be co-dependently evolving with our technology.