I did not know 5-HTP was in wallnuts, but I actually had a negative reaction to it anyway, heart palpitations and feeling like i was in a perpetual state of coming up for hours! Ha. Upon doing some research it seems serotonin is not the culprit, and that reaction happens when your system is flooded with too much. I have more reason to believe that dopamine is at play rather and rok's tip spurred me to look into that anyway so i am working to increase dopamine levels naturally instead.
Luckily where i live the water is not fluoridated. However we do use a water filtering jug to remove other impurities :)
Fluoride in the water is such an immense topic however, and rather alarming :/