L-Theanine is very commonly found in tea and is an amino acid, biochemically related to glutamine. The psychoactive properties of theanine are derived from the ability to cross the blood brain barrier. It has been proven that theanine can reduce stress, promote relaxation and improve alertness and mood when imbibed together with caffeine, a natural combination found in any tea, especially green tea. Gamma-aminobutyric acid levels are increased, when theanine is ingested or imbibed, as are serotonin and dopamine levels. It is believed that l-theanine is aiding the immune system by strengthening the capacity of delta T cells. Laboratory tests have proven that blood pressure reduction and lowering of 5-hydroxyindoles in the brain are promoted by theanine.