I’ve got a pretty severe sensitivity to – of all things – sugar. (I know, “sugar” isn’t very precise, but I’m pretty sure it’s either glucose, fructose, or sucrose.) I virtually never eat anything with added sugar or anything with any significant amount of natural sugar. And I’ve eaten that way for like 20 years now. I’m practically blind to half the produce department (any “sweet” fruits like apples, pears, cherries, grapes, oranges, etc) at the grocery store, let alone the candy isle.
My wife was vegan for several years and went back to vegetarianism. She was always tolerant of my omnivorous diet, so long as I was mindful of cross-comtamination. I got used to eating her choice of proteins as well, and now I eat nearly as much vegetarian substitutes as I do meat. But holy fuck, does red meat tear me up now with the most painful and absurdly disgusting smelling farts, with a volume and frequency so great that it could blow down a brick townhouse.