Tryptophan

Tryptophan is an amino acid needed for growth and maintenance of the proteins, muscles, enzymes, and neurotransmitters. The body uses tryptophan to help make melatonin and serotonin. Melatonin helps regulate the sleep-wake cycle, and serotonin is thought to help regulate appetite, sleep, mood, and pain. The liver can also use tryptophan to produce niacin (vitamin B3), which is needed for energy metabolism and DNA production.