Tryptophan itself as a component of food is mentioned however, as well as tryptophan supplementation. I'd consider 5-htp and L-tryptophan to be under that "tryptophan supplementation" umbrella. The difference between 5htp and l-tryptophan is that the former doesn't require a transport molecule to get past the blood-brain barrier, so it [citation needed] converts to serotonin quicker, whereas with l-tryptophan there's a rate-limiting effect. 5-htp for faster effects, L-tryptophan to prevent building a tolerance to the extra serotonin.