[tjradcliffe]

The belief that the human nutritional optimum is narrow and deep, so that "complete elimination of food X" and "total focus on food Y" will enormously enhance your health is a crypto-creationist argument, as it requires a complete rejection of everything we know about evolution in general and human evolution in particular.

Omnivores like humans evolve with broad, shallow nutritional optima. Humans are happy with a diet of simple starches (metabolically almost indistinguishable from refined sugars) or a diet of fatty meat, and do pretty much the same on almost everything in between. There are statistically measurable variations, but the optimum is so broad and shallow--as our evolutionary history would predict--that it is full of really shallow local optima that are due purely to noise. Crypto-creationists glom onto these shallow local optima and make out like they have incredibly deep minima hidden in their midst, which is utterly implausible unless you reject evolution as the force that shaped us as species.

[Chevalier]

I'm not sure that equating creationism with nutrition makes sense. Nor does the rise of grain necessarily signal evolutionary adaptation. It seems quite possible that humans can survive and thrive on sub-optimal nutrition.

In fact, Jared Diamond quite convincingly demonstrates that hunter-gatherers, with their meat-and-vegetable diets, were far healthier than their agricultural cousins. But the abundance that resulted from agriculture (along with the perils of nomadic hunting) allowed farmers to have far larger families and eventually drown out hunter-gatherers through sheer demographic superiority. It doesn't mean that grains are ideal for human consumption, only that agriculture allowed population growth and urban density that eventually crushed the hunter-gatherer lifestyle.

We could live on Twinkies if required. We are, as you pointed out, omnivores. The relevant question is what diet is most optimal for human health.

[revelation]

I think you didn't exactly read the answer? Humans can survive on much any diet, and the differences between them are mostly insignificant, certainly as it pertains to criteria that apply to people sitting most of the day doing mental work.