Designs for Health L-Theanine is a 100% pure, easy to dissolve, excipient-free, tasteless and colourless powder. It is a non-protein bound, free amino acid that is similar in chemical structure to glutamic acid. It can be found in such food sources as green and black tea and mushrooms. L-Theanine is the predominant isomer in green tea, making up around 1-3% of the dry weight of tea leaves. It also accounts for around 50% of green tea's total amino acid profile and is responsible for the unique flavour. When exposed to sunlight, Theanine in tea leaves is converted to polyphenols. Plants grown out of direct sunlight, therefore, are naturally higher in theanine. The absorption site for L-Theanine is the small intestine, and peak concentration is reached within around 50 minutes. Once absorbed, L-Theanine is broken down into glutamic acid and ethylamine.