Gamma-aminobutyric acid (GABA) is a neurotransmitter in the brain that plays a crucial role in reducing neuronal excitability. It helps to inhibit nerve transmission, which can lead to a calming effect on the nervous system. This function is essential for maintaining balance in brain activity and can influence mood, anxiety, and sleep. GABA is produced from glutamate, another neurotransmitter, through the action of the enzyme glutamic acid decarboxylase. It is found in various foods, such as fermented products and green tea, and is also available as a dietary supplement. GABA's calming properties make it a focus of research for anxiety and stress-related disorders.