Can Smart Coffees Really Boost Your Brain Daily Mail L-theanine is a non-essential amino acid derived from the camellia sinensis plant species. it was first discovered circa 1950 in which it was noted within the contents of green tea; it serves as a building block for proteins and is also present in other types of tea (e. g. black tea). for generations l-theanine has been utilized as a natural supplement to treat anxiety and tertekan, and has been investigated as a cognitive enhancer (nootropic) when administered synergistically with caffeine. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances. medical disclaimer. This ties in with the variable of individual variation, but it is necessary to consider potential interactions between l-theanine and other drugs (or supplements). if youre a heavy drinker of alcohol and supplement with l-theanine, it is important to consider the fact that these substances could int...