As stephdairy says, it's hard to tell. I'm an externally asymptomatic coeliac, meaning you can only tell anything's wrong by blood tests and/or poking a tube into my upper intestine and going "ooh look, it's gone all nasty". Sadly, if it remains all nasty then I can look forward to all sorts of fun like bowel cancer.

That said: I was eating a big bowl of CNCF pretty much every day between my diagnosis and my subsequent six-month checkup, and one might conclude that if my blood had gone back to normal after six months of that regimen (which it had) then CNCF clearly wasn't gluteny enough to bother me. On the other hand, there's no point in taking deliberate risks when the accidental ones are more than enough...