Green tea has been recognized for centuries as having relaxant properties. l-Theanine, a unique amino acid derived from tea, provides the characteristic taste of green tea. l-Theanine also has also discovered as the biologically active constituent of green tea responsible for promoting relaxation. In a preliminary non-clinical study, an l-theanine solution enhanced alpha wave production in the occipital and parietal regions of the brains of volunteers. These observed patterns are considered to be an index of relaxation. Furthermore, it did so rapidly and without causing drowsiness. In two additional studies, alpha waves were also shown to be detectable soon after l-theanine administration. l-Theanine also is useful for supporting healthy cellular function. Preliminary research suggests that l-theanine may be helpful for premenstrual support including healthy mood. Furthermore, l-theanine has been reported to moderate the effects of caffeine on the central nervous system. l-Theanine's safety is supported in studies and by its long history of safe consumption in tea. Pure Encapsulations's l-Theanine is Suntheanine , the brand which has been used in scientific studies.