Solgar ® L-Theanine 150 mg contains the non-dietary amino acid and natural phytochemical L-Theanine (commonly found in green. black or white tea. L-Theanine does not fall within either essential or non-essential amino acid categories because it is not common in the diet and cannot be made by the body. It has a chemical structure similar to a neurotransmitter type of amino acid, glutamine, which naturally occurs in the body. L-Theanine is able to cross the blood brain barrier and can influence brain wave activity.