My wife has a bunch of yet unconfirmed food intolerances, but her journey to work out what it is exactly has really opened my eyes to how complicated this is. To the point that I struggle to think a system as simple as you point out is feasible. Things like the ripeness of an avocado or banana can be trigger, or if a protein is seared vs boiled/braised. It's also not binary, a trigger won't always immediately cause a reaction. It's like the body has a threshold of a given thing it can process, and a half-life on how quickly it metabolises and can take on more. But that half-life itself is variable based on other things you're ingesting. So are you intolerant of bananas? Or is it actually amines and the reason you had a reaction is because you also had dark chocolate 4 days ago, and a charred T-bone the day before that? Or maybe it actually is the banana, or more specifically the chitinase in it. Let's test it by seeing if you react to a higher intake of green beans too.
Each time there's a reaction if you want to try an actually isolate the cause it's back to nothing but plain rice and boiled chicken breast for literally weeks. Then from a neutral state you can introduce the new hypothesis, but given the whole half-life aspect you need to work out whether it's a certain amount of that food over a certain amount of time. If you get a reaction, there's still probably two or more reasons why (e.g., amines vs chitinase vs potassium vs whatever) so now you start again to isolate that. And/or you still need to work out the interaction with other foods. Over and over it repeats. It sucks.
At some point you also want to actually enjoy your life and not spend years being a walking diet experiment.
How can you tell any of these conclusions are valid and it’s not just pattern-matching on random events? Especially if you keep finding that whatever you theorized from some experience is disproven by what happens next.
Each time there's a reaction if you want to try an actually isolate the cause it's back to nothing but plain rice and boiled chicken breast for literally weeks. Then from a neutral state you can introduce the new hypothesis, but given the whole half-life aspect you need to work out whether it's a certain amount of that food over a certain amount of time. If you get a reaction, there's still probably two or more reasons why (e.g., amines vs chitinase vs potassium vs whatever) so now you start again to isolate that. And/or you still need to work out the interaction with other foods. Over and over it repeats. It sucks.
At some point you also want to actually enjoy your life and not spend years being a walking diet experiment.