Peter Gibson, one of the folks who first identified the possibility of gluten sensitivity outside of celiac disease, tried to replicate and nail down his earlier results— and it didn't happen. The nocebo effect set in, and what associations with diet there were correlated not with gluten, but with "fermentable, poorly absorbed short-chain carbohydrates."

The article about this, replete with links: Ross Pomeroy - Non-Celiac Gluten Sensitivity May Not Exist.