In my mind evolution says...
I think that our bodies are designed by evolution to work most efficiently on what food was available for the bulk of our existence (ie before civilization and its massive monoculture style of food production).
Its a well known trend that the massive amounts of red meat Americans eat leads directly to many problems such as hypertension and heart attacks. Its fairly well known now that "carbs" are bad and at the very least highly refined sugars burn really quickly and create an addictive situation of peaking and crashing in those who consume lots of it.
As far as whats good for us to eat? Who knows? Scientists can't even make up their own minds on the topic and there's hardly enough credible research to state what an ideal diet would consist of. That also completely ignores any of the information that is put out by the people who make money of the situation, like say cattle producers who can put implants in beef to gain $80 in pure profit per steer without having any desire to learn about the long-term effects of their actions.
I think the obvious solution is to try to figure out how nature designed us to eat and eat that. None of this crap where everyone goes on weird diets and waits for someone to tell them they're doing it all wrong.
I think eating massive quantities of anything one thing would be a poor idea, since I don't think we were provided with large quantities of any one food in our natural state. To me, I would think that the more diverse the better. The less crap that man changed about the food the better. The less pesticides the better. The less fertilizers the better. The less chemicals added the better. I'm pretty confident that even our smartest and our brightest can't predict exactly how all these added chemicals affect us over the course of a full lifetime, so why trust their judgement blindly or selectively choose which ones to listen to?
If you want a slightly easier solution, find a culture that lives long, healthy lives and eat what they eat.
