L-Theanine is a non-proteinogenic amino acid structurally similar to glutamate, primarily found in tea leaves (Camellia sinensis) and some mushrooms. It is known for its role in promoting relaxation without sedation by modulating neurotransmitter activity, including increasing GABA, dopamine, and serotonin levels while influencing alpha brain waves. Chemically, it is the ethylamide derivative of L-glutamic acid. It exhibits antioxidant properties and has been studied for potential benefits in stress reduction, cognitive function, and sleep quality. Theanine is absorbed rapidly in the small intestine and crosses the blood-brain barrier. It is commonly used as a dietary supplement and food additive for its umami flavor and calming effects.