Gamma-aminobutyric acid (GABA) is a major neurotransmitter used in the human central nervous system. As the body's most important and abundant inhibitory neurotransmitter, GABA acts to mitigate the overproduction of stimulatory neurotransmitters. Stimulation of GABA receptors leads to relaxation as well as the induction and improvement of sleep.
L-theanine is a known constituent of green tea and has been shown to cross the blood-brain barrier, leading to increased alpha wave activity, associated with relaxation responses through stimulation of GABA receptors. L-theanine has been shown to dampen cortisol production and reduce carbohydrate cravings.