The essential amino acid L-tryptophan helps support relaxation, restful sleep, and positive mood regulation. It participates in the synthesis of melatonin and serotonin, hormones associated with sleep/wake cycles and stress response. L-Tryptophan can also support immune system function due to its role in the production of kynurenines, molecules that regulate immunity. Additionally, L-tryptophan can convert to niacin in the body, which helps maintain circulation, a healthy nervous system, digestion, and metabolism. Source Naturals L-Tryptophan is rigorously tested to guarantee optimal quality.