GABA (gamma aminobutyric acid) is a non-essential amino acid found mainly in the human brain and eyes. It is considered an inhibitory neurotransmitter, which means it regulates brain and nerve cell activity by inhibiting the number of neurons firing in the brain. GABA is referred to as the brain's natural calming agent. By inhibiting over-stimulation of the brain, GABA may help promote relaxation and ease nervous tension. NOW provides only the naturally occurring L-form as found in food and in the body.