Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in our central nervous system. Glutamate and glutamine are precursors of GABA, which can be thought of as the yin to glutamate’s yang: while glutamate fires neurons up, GABA slows them down, having a calming effect on the nervous system. GABA therefore plays a key role in anxiety, mood and sleep. Recent research shows that GABA also plays a role in our gut-brain connection and that the neurotransmitter can be both consumed and produced by certain bacteria in the gut.Schor, J. J. and Bloom, R. A. (2017). GABA: Gamma-Amino Butyric Acid. [online] Denver Naturopathic Clinic. Available at: http://www.denvernaturopathic.com/news/GABA.html [accessed 17 Oct. 2017]. WebMD. (2017). GABA: Uses and Risks. [online] Available at: https://www.webmd.com/vitamins-and-supplements/gaba-uses-and-risks [Accessed 19 Nov. 2018]. Integrative Psychiatry. (n.d.). Natural GABA. [online] Available at: https://www.integrativepsychiatry.net/natural_gaba.html [Accessed 19 Nov. 2018]. Pokusaeva, K., Johnson, C., Luk, B., Uribe, G., Fu, Y., Oezguen, N., Matsunami, R.K., Lugo, M., Major, A., Mori‐Akiyama, Y. and Hollister, E.B., 2017. GABA‐producing Bifidobacterium dentium modulates visceral sensitivity in the intestine. Neurogastroenterology & Motility, 29(1), p.e12904. Tapia, R. and Gonzalez, R.M., 1978. Glutamine and glutamate as precursors of the releasable pool of GABA in brain cortex slices. Neuroscience letters, 10(1-2), pp.165-169.