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Frankly, I think the question of "how must gluten is too much" is one that
burns in the minds of all celiac patients (or in may case, parent of a
celiac patient) who are not so sensitive that any exposure causes an
obvious adverse reaction.  Our ongoing attempts to adhere to a "zero
gluten tolerance" diet has quality of life implications, and it is
perfectly natural and certainly not harmful to anyone to simply ask the
question, is there a safe quantity?  I myself have asked the question, and
to my knowledge there is no answer to it.