Product Details  L-theanine is extracted from green tea. It has a significant effect on the release or reduction of neurotransmitters.  L-Theanine is an amino acid which can be found naturally in green tea. It has been shown to promote relaxation and a restful state without causing. It is suggested that L-Theanine can increase certain neurotransmitters and alpha waves produced by the brain which encourage a calming effect.