Whitefox:

That's a good point about sweet potatoes.  It's also important to note that there are many different "sweet potatoes", which vary greatly in nutrient and antinutrient content.  (White potatoes are the same.)

All plants contain antinutrients.  The important question is "Did our ancestors eat them frequently enough, and for enough generations, that an ability to metabolize or eliminate the antinutrient has arisen and been universally selected for?"  For instance, aspirin is toxic to cats, who have been purely carnivorous for so long that they've lost the ability to metabolize that class of plant toxins.

That is why I'm more suspicious of antinutrients in Neolithic foods: based on what we know of issues like gluten intolerance, celiac, Hashimoto's, etc., we know that the process of adaptation to Neolithic toxins is incomplete at best.  Thus my point: just because we eat something for a few months and "feel fine" doesn't mean it's healthy to eat. 

(There was a lot of that going around the paleo community when I wrote this article, e.g. "I ate corn for a few months and I feel fine, therefore corn is healthy to eat."  Fortunately, most of the people involved concluded paleo was "too limiting" for them and have explicitly abandoned the term...though a few of them refuse to go away, because they know the paleo community is where the action is.)

And yes, the jury is still out on most of these issues.  Whether and how often you "cheat" is a personal decision that I can't possibly make for anyone.

JS