I have never noticed caffeine as an issue for my feet. I get really sickeningly tense from too much caffeine. So I avoid it most of the time. I have never been able to tolerate coffee either...it upsets my GI tract terribly. But I do tea in the mornings sometimes.Usually it is decaf green tea or peppermint however, for me.

What really sends me over the edge however, is MSG in foods. So I read all labels and avoid it like the poison it is.
Some Lays products now are MSG free... Simply Tostitos, is one.
Nightshade veggies also will cause lots of burning pain for me...
even paprika spice will do it. So it pays to read the labels of all the foods you eat-- which is tough as far as restaurant food however. Soups and gravies, typically are heavily MSGed still.
And you just have to do trial and error to monitor your reactions to restaurant food. Usually the better the taste, the more MSG may be in there. Glutamate sets off the NMDA receptors:
http://en.wikipedia.org/wiki/NMDA_receptor

The NMDA receptor antagonists, can be used for pain issues.
Magnesium is one....and that is why the lotion works so well.
http://en.wikipedia.org/wiki/NMDA_receptor_antagonist