Tryptophan (L-Tryptophan) is an essential amino acid that cannot be produced by the human body and must be obtained through your diet, primarily from animal or plant based protein sources. Tryptophan plays a role in the production of serotonin, a mood stabilizer, melatonin, which helps regulate sleep patterns, niacin or vitamin B-3, and nicotinamide also known as vitamin B-3. Tryptophan elimination experiments have shown that tryptophan has a beneficial impact on: Mood, depression, Learning memory skills, visual cognition, Aggression control.