Tryptophan is an essential amino acid.
Vitamin B6 is needed for the proper use of this amino acid.
Athletes: A high intake of tryptophan (especially in conjunction with a low-protein, high-carbohydrate meal) boosts serotonin levels, which might benefit athletes by increasing pain and endurance tolerance.
Depression: By increasing serotonin levels, tryptophan acts as an antidepressant.
Pain: Tryptophan supplements increase pain tolerance.
Sleep: Tryptophan shortens the time it takes to fall asleep and improves the quality and length of sleep. However, it does not necessarily prevent awakening in the middle of the night or sleepiness the next morning.