L-theanine is a non-protein amino acid mainly found naturally in the green tea plant (Camellia sinensis). L-theanine is the predominant amino acid in green tea and makes up *0% of the total free amino acids in the plant. The amino acid constitutes between 1% and 2% of the dry weight of green tea leaves. L-theanine is considered the main component responsible for the taste of green tea, which in Japanese is called umami. L-theanine is marketed in Japan USA, and European as a nutritional supplement for mood modulation.