I had a very similar takeaway. As a kid, I used to get stomach aches and a long list of other issues. Fast forward after a bunch of tests as an adult and the r

I had a very similar takeaway. As a kid, I used to get stomach aches and a long list of other issues. Fast forward after a bunch of tests as an adult and the results reported to me by a doctor spelt out that most artificial sweeteners are effectively poison to me. If I want a headache, stomach ache, etc I just consume one of the many sweeteners out there. The "hyper-sweet" taste and after-taste I get from most artificial sweeteners for me is a signal of poison or bad food. Its a clear signal to avoid that food in future. My question is the same: I wonder if D2O would have that same kind of "twisted" sweetness? Secondary questions: I wonder if our ancestors did the same? Noticed that they didn't feel well and that was enough to tip the selection balance such that we now have the ability to detect D2O? How subtle would that effect be? or is just it tied into a specialised "anti-poison" set of structures we've got to detect bad-food? I think this is more likely. D2O is bad water. We have senses for other kinds of bad water as well.