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

I had commented to the poster that flax was a natural laxative, http://www.mayoclinic.com/health/flaxseed/NS_patient-flaxseed, but wasn't included in the summary.  Even if one "used to eat Mesa cereal without problems", other factors can change that, including your own body changing, stress, and more than normal flax than you are "used to".  After all, I was once "used to" wheat!  
I think it's unfair to quickly say "gluten contamination" when so many other people have no problems eating Mesa.  In general, people must realize that while gluten is harmful to us with Celiac, it may not be the one and only blame in other foods that don't seem to agree with us.  

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