L-theanine, also known as L-γ-glutamylethylamide and N5-ethyl-L-glutamine, is an amino acid commonly found in the leaves of the green tea tree. It has a relaxing and stress-reducing effect, while simultaneously improving concentration. Theanine increases serotonin, dopamine, GABA, and glycine levels in various areas of the brain, as well as BDNF and NGF levels in certain brain areas. Theanine is reported to promote alpha wave production in the brain, which are associated with states of deep relaxation as well as increased selective attention. It synergizes very well with caffeine, reducing the negative side-effects of caffeine stimulation.