Thomas Edwards82 said:Personally, even though I don't have an allergy to aspartame or anything like it, I feel like crap all day after just two sips of Diet Coke.
And whenever I feel sick like that—and when I start burping like crazy—I check the label on whatever I just drank, and what do I find? Good old phenylalanine.
My solution: I don't touch anything with artificial sweeteners. Period.
Look, since you only feel sick from Diet Coke (and other artificial sweeteners), you can't really pin the blame on phenylalanine. It’s an amino acid found in basically every protein source. By that logic, you should be feeling sick from eating meat, soy, or milk too...
Besides, phenylalanine is only harmful to people with phenylketonuria. In the US, they screen newborns for that condition right at birth because those kids have to stick to a special diet from day one. As Andrew Anderson6 mentioned, if they aren't managed, they end up with an Intellectual Disability.
Anyway, do you go out and poop black after you eat something containing phenylalanine? No. So your metabolism is handling that amino acid just fine.
It seems to me you’re feeling sick from Diet Coke for some other reason entirely—maybe you can't handle the acidity, maybe you just hate the flavor, or maybe it's the caramel coloring...