Nutricost L-Tryptophan provides a great source of this essential amino acid that is so important in human nutrition. L-Tryptophan is an essential amino acid, which means that it is not synthesized by the body and must be obtained from one's diet. Nutricost, located and headquartered in the USA, only uses the best ingredients to ensure maximum quality and to help you feel your best! By keeping our supplement recipes simple and clean, you get the best experience possible with Nutricost.