[jvdh]

Second hand evidence, but what I've heard is that you'll know pretty quickly whether you have a response or not. Cramping pain, nausea, diarrhea, feeling miserable, you name it.

And this was just from eating a small treat, not even a full meal. So if you want to know for certain, follow the diet for some time, and then feast on gluten.

[carbocation]

Thanks. Hopefully jerf can provide some citations for the diagnostic utility of this. It doesn't sound promising, honestly.