"Others here suggest saying you have gluten intolerance or some such condition.."
unless one actually has this condition...why lie?
regardless if they believe you, it's still making a big deal of something that shouldn't be a big deal.
mrd232's got the right of it...don't say anything unless someone says something first.
if they ask why..just tell 'em you're fine with what you have or whatever. no need to get into the PB-rant or make up excuses (gluten intolerance) and so forth.