The thing with foods like corn, millet, and beans is that, in a traditional setting, they are prepared very differently than they are in a modern setting. For example, corn was processed with lime (the mineral, not the fruit) to make things like tortillas; the lime processing unlocked a b-vitamin that was previously bound up and not usable by the human body. When cultures rely on corn as a staple food and DON'T use this lime processing method, they end up developing a b-vitamin deficiency disease known as pellagra (this was actually quite common in the southern US in the early part of the 20th century).

Millet was usually fermented and then made into a porridge or gruel. The fermenting process upped the vitamin content significantly and also broke down the phytates in the grain.

Beans were also soaked and allowed to begin to sprout before being eaten.

I think that WAP came to believe that many of the downfalls of the modern diet had to do with fat-soluble vitamins specifically - A, D, E, and K. That's why he recommended cod liver oil to deficient children, as it is a rich source of A and D. I believe he also recommended raw butter oil as a supplement as well.

If you want to see a bit of hands-on information on how to do this stuff, you should read Nourishing Traditions by Sally Fallon. She's the current leader of the Weston A Price Foundation (WAPF).

So the key is to maximize the good and minimize the bad with whatever food you wish to eat. And of course you should pay attention to your own body's cues; it doesn't matter if African tribes drank raw dairy if you are allergic to casein.

This really is fascinating stuff, isn't it? Sorry if I come off sounding harsh or anything, I tend to just go into academic mode a lot when I talk about this stuff.