My husband has MS and after developing MS developed some weird food sensitivities that sound like what you describe. I honestly think its the weird neurology thing going on and who knows if it is even testable.
He found that eating beef would make him weak and fatigued, his stomach bloated. Then chocolate started to bother him. Both foods he had eaten fine and then he couldn't tolerate.

My story is odd. After getting CRPS I can't drink my diet sodas. I used to drink them every day and now they taste funny. A few other things taste off to me now too, though I can't remember right now what they are. So my sense of taste got oddly messed with. And while I know giving up Diet Pepsi isn't the end of the world... I miss it.