I have been tested (blood antibodies) twice and was negative both times, and once I feasted on wheat germ for weeks ahead of time...just to really challenge my system (to no ill effect). I am negative, so, I don't go gluten free. Neither do I plow down wheat for the sake of chowing on whole wheat.
I have an EGD and mannometry coming up due to esophagel problems, so we will see what that yeilds. I do have substantial autonomic abnormality and symptomotlogy.

My GI guy refers to the GI system as the second brain. I always remind him of what the tail end of the GI system is called, LOL. (We do get a long quite well).

Some folks feel much better gluten free. I noticed no difference. If it makes a difference, I would certainly follow it. When they do my next colonoscopy, I will ask for villi sampling which is apparently the only fool proof way to determine celiac status.

You know constipation and slow transit, can be small fiber neuropathy-autonomic.

Oh, I did have a normal Vitamin D level!! I am awful, as I don't use sun screen...I use a hat and long sleeve shirt, to prevent burning....or if cycling then I use sunscreen, so I do get my sun in the summer....I am out all the time. I did start taking vit D but then got sloppy, but what I took must have been good enough. I also take B-12, sublingual...because my stomach has never been right.