You've done the homework. Good.

"a) That an element is present does not make it necessary."

There are some we get plenty of so it is not concern.

"b) If the mechanism by which it functions is not understood, then neither is the difference between therapeutic and toxic levels."

Hold on there. That statement is off somehow. There is always a difference between therapeutic and toxic. It is true however, that some are more important than others. What's more, the levels needed or toxic will vary person to person especially among those with different lineage. There is proof of this though indirect.

"c) Enough may be enough, but too much is quite often deadly. And in the case of some - very subtly deadly."

True of anything. Years ago someone did die of water poisoning. It was a water drinking contest, like they h ave taco, pizza or hot wing eating contests. I am not sure if the dead guy won...

"d) How individuals metabolize varies. And therefore tolerance to some elements. Cats, dogs, and many primarily carnivores cannot tolerate common foods humans enjoy. And birds will eat choke-cherries, mistletoe berries, bittersweet and hemlock with no ill effects. Hummingbirds and bees will fertilize foxglove and acanthus without consequence. "

I think I said that about people, but it applies n spades to different animals. Dogs can eat damnear anything, try it. Koala bears only eat eucalyptus leaves, how they get along without some of the minerals which MUST be deficient in those leaves is unknown, at least to me. Likewise, how do Eskimos get vitamin C ? Humans lost the ability to manufacture C in body they say I think about 10,000 years ago. Why ? How ? And did this supposedly happen to all humans in the space of a few years or what ? It almost can't be environmental, that leaves evolutional. Right ? Not quite sure on that one. I have looked into that and found that they DO have a source of vitamin C, in whale skin. Vitamin C is destroyed at 374F, so I imagine they're not deep frying it and if you've eaten skin, fried is the way to eat it. So they really sit around and eat whale skin ?

The database I offered does contain a significant amount of information on what some of those minerals actually do in the body. It gives information on symptoms of deficiency, diseases that coincide with certain deficiencies, recommended level and sources. The problem is it only has that information on about 20 of them. there are quite a few more. Also, there are a few about which they have little information at all.

Since this hijack was successful (hi Raul, tell Fidel I send him my best) I might excerpt from that to illustrate what is in it. I used to host the files on Dropbox but me and them don't see eye to eye on a couple of things.