L-Tryptophan is an essential alpha-amino acid that is a precursor to the neurotransmitters serotonin and melatonin. Supplementation with tryptophan has been shown in numerous clinical trials to be safe, well-tolerated, and supportive of well-being, calmness, relaxation, sleep, and appetite control.† For best results, take tryptophan on an empty stomach, or with a small serving of carbohydrates.