It seems to be a nocebo effect – the self-diagnosed gluten sensitive patients expected to feel worse on the study diets, so they did.

Don't be stupid, be a smarty come and join the Nazi Party!

A chill waved over my consciousness as my worst nightmare erupted into reality.

[…] the barriers, which to them limit the view, and give to it, together with the contraction, all the distinctness and definite outline of limitation, are, in nine cases out of ten, the product of their own defective and aberrating vision, and not real barriers at all.