>Various plant foods (and some animal foods) contain compounds
        >that are toxins or antinutrients.  Stahl refers to these as
        >"secondary compounds."  What makes a food inedible is not the
        >absolute presence or absence of secondary compounds but the
        >*level* of them.

That's interesting - would the essential oils in herbs and the like be
considered 'secondary compounds'?  That would explain why those substances
act as a deterrent to insects and some animals, but not to humans, unless
eaten in excess.  I believe parsley is one herb that is toxic if you eat too
much.

And of course many secondary compounds are actually beneficial to humans -
thus the benefits of, for instance, green tea and herbal medicines.

Anne Boyd