This is an important point that I have wondered about.

When we don't eat carbs, our body waits around for carbs for awhile, and then eventually, depending on critical depletion (eg probably sooner and more severely for a 500# person on 5 carbs a day, than a 130# person on 20 carbs a day) shifts into ketosis.

Well what if the more variety we have in our diet, the more trace minerals and more our body 'waits around for' because it figures it'll get 'em eventually? What if the body is actually capable of making or substituting some things itself, chemically, but it has to think it needs to do that, in order for it to happen? And maybe needs certain primary building blocks (say extra protein/amino acids/etc.)?

I ask because the eskimo for example and some other native cultures have had a pretty limited, mostly-meat/fat-only diet, and yet they were not extinct from 101 deficiency diseases, and I think it merits asking why. Why should humans need to eat broccoli or almonds for nutrients, if people not eating those seemed to get along just fine.

Don't get me wrong, I like fruits, veggies, dairy, etc. -- I'm in no danger of becoming zerocarb anytime soon -- but from a logic standpoint, I'm having a hard time working that out in my head. I don't disagree that in modern research, modern people 'need' nutrients that veggies-etc. supply. What I don't understand is why we need them so much when it appears some native peoples didn't need them at all.