I tried L-Tryptophan several nights, thought one of the other substances was what kept me alert-awake. (I was taking several things at once - B3, herbs, etc, in desperate effort to get some sleep! Bad idea for figuring what is causing a worse problem instead of helping) I was having strange feelings in my chest which I now know to be heart palpitations.
Thinking no sleep meant I wasn't taking enough L-Triptophan (and that one of the other tools was causing the strange chest thumps), I upped from 500 mg to 1000 mg (2 pills) and took only L-Tryptophan (to eliminating, I thought, whatever was causing the chest spasms). But an hour after I got to bed wow was my heartbeat crazy! Like my whole chest was throbbing! Felt like a superslow beat 5 times the usual strength, but wrist pulse revealed a weak pulse beat in between the super big ones, so the rate was normal but the strength unusual. Really scary to have a resting heartbeat that intrudes on your awareness! Got up and searched for the half life - 1-2 hours. That was reassuring. An hour later my heartbeat was still too strong but far less so. (Food based L-Triptophan has a 10-12 hour half life because it's bound to protein; the pure supplement has a short half life.)
BTW, L-Triptophan supplement wearing off fast means it might be good for helping some people get to sleep but not keeping them asleep.