This tea contains a high percentage of Gamma-Aminobutyric Acid (GABA), known for having a calming effect on the nervous system. It has a wonderful, soothing flavour. Tea plants are known to produce leaves especially high in glutamic acid. About two weeks prior to plucking, GABA oolong leaves are partially shaded, which causes increased production of this substance. During the oxidation-phase of production, all oxygen is replaced with nitrogen gas, whose presence causes the glutamic acid to be converted to Gamma-Aminobutyric Acid. To meet Japanese standards and be labeled GABA Tea, the finished product must contain at least 150mg of GABA per 100g dry weight.