<<Disclaimer: Verify this information before applying it to your situation.>>

Oops!  Guess I wasn't thinking...  The consensus is that there is no
problem eating mushrooms grown in wheat bran - any more than there is
with eating chicken or beef that have ingested wheat in some form.

Sage comments follow:

First from the expert:  Executive Director, Dietician and Celiac

The answer to your question is no -the mushrooms will not contrain
gluten.

Cynthia Kupper, CRD
Gluten Intolerance Group

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Do you worry about eating steak because the cow it came from might have
been grain fed?

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The short answer is "no."  Think about it for a second.  If a sheep eats
barley, does the meat have gluten?  If you eat chicken, does your tissue
resemble bird tissue?  Nope.  In normal situations, an organism breaks
down proteins (like the gliaden we are allergic to) and rebuilds them
into "self."  Obviously, there are exceptions, such as soluble materials
that get taken up by a plant along with water (remember the elementary
school experiment where you put a white flower in green water and it
turned green?), but gluten is not soluble to any real extent.

******

The mushrooms will leave the gluten behind.  They are unable to carry it
in their cells just as chicken do not contain gluten from all the wheat
in their chick scratch.

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I think that we will go crazy if we have to start thinking about compost
contamination. If we don't have to worry about grain-fed beef or
chicken, I wouldn't think we had to worry about growing medium for
vegetables. Let us know what you learn, particularly if you get some
hard facts instead of opinion.

*****

no - don't worry. If the mushroom would take in any gluten it would be
broken down and re-assembled.  Think of the cows and chickens eating
wheat and wheat middlings.  No problem for us.

**********

So, no need to worry.  Can't wait for those babies to get bigger so I
can eat them.

Thanks everyone.

Diane