Gamma-Aminobutyric acid (GABA) is an amino acid produced naturally in the brain. GABA functions as a neurotransmitter, facilitating communication among brain cells. GABA’s big role in the body is to reduce the activity of neurons in the brain and central nervous system, which in turn has a broad range of effects on the body and mind, including increased relaxation, reduced stress, a more calm, balanced mood, alleviation of pain, and a boost to sleep. (1) 

First of all, GABA boosts the release of growth hormones by improving the quality of sleep since nighttime growth hormone release is linked to sleep quality and depth. (2, 3) It shortens sleep latency and increases non-rapid eye movement (REM) sleeping time. (4) GABA also reduces acute psychological and physical fatigue by suppressing sympathetic response and increasing parasympathetic response under stressful tasks. (5, 6) Experts estimate that as much as 75 percent of the human growth hormone is released during sleep, especially during the first phase of slow-wave sleep. (7) In fact, GABA elevates resting and postexercise irGH (Immunoreactive growth hormone) and ifGH (Immunofunctional growth hormone) concentrations. A study asked 21 healthy males to take a supplement with whey protein or whey protein plus GABA once a day for 12 weeks. The researchers found that the combination of whey protein and GABA increased levels of growth hormone compared to whey protein alone. (8) After GABA ingestion elevated peak concentrations of both hormones by about 400%. (9) One study showed the person who was given 300mg of GABA before going to bed fell asleep faster than those who took a placebo. The GABA users also reported better sleep quality after one month of using the supplement. (10) 

In addition, GABA supplements might help to build muscle and assist in workout recovery. GABA also has partly promoted muscle protein synthesis, leading to an increase in whole-body fat-free mass by elevating resting plasma GH concentrations. Oral GABA supplementation promotes protein synthesis in various parts (e.g. the brain and gastrocnemius muscle) and higher plasma GH concentrations at rest in rats. (11)High levels of GABA have also been linked to high intelligence and cognitive performance in a brain imaging study of healthy people. (12) For example, a 2015 study found that taking 800 milligrams (mg) of GABA supplementation per day enhanced a person's ability to prioritize and plan actions. (13) 

Also, research shows that GABA might play a key role in protecting against depression and anxiety. For instance, a study published in the journal Biological Psychiatry in 2010 indicates that people with major depression may be more likely to have low levels of GABA. (14) And a 2009 study showed that increasing GABA levels may be useful in the treatment of conditioned fear. These results are consistent with the fact that GABA is the primary calming (inhibitory) neurotransmitter in the brain. (15) Another study found that taking 100 mg of GABA daily helped reduce stress due to mental tasks. (16) 

References: 

1. Michael J Breus. 3 Amazing Benefits of GABA Psychology Today. 2019 Jan; Retrieved from https://www.psychologytoday.com/us/blog/sleep-newzzz/201901/3-amazing-benefits-gaba

2. Gottesmann C. GABA mechanisms and sleep. Neuroscience. 2002;111(2): 231-9. 

3. Honda Y, Takahashi K, Takahashi S, Azumi K, Irie M, Sakuma M, Tsushima T, Shizume K. Growth hormone secretion during nocturnal sleep in normal subjects. J Clin Endocrinol Metab. 1969 Jan;29(1):20-9. 

4. Yamatsu A, Yamashita Y, Pandharipande T, Maru I, Kim M. Effect of oral γ-aminobutyric acid (GABA) administration on sleep and its absorption in humans. Food Sci Biotechnol. 2016 Apr 30; 25 (2): 547-551. 

5. Fujibayashi Mami, Kamiya Tomoyasu, Tagaki Kinya, Moritani Toshio. Activation of Autonomic Nervous System Activity by the Oral Ingestion of GABA. Retrieved from https://ci.nii.ac.jp/naid/10021177751

6. Kanehira T, Nakamura Y, Nakamura K, Horie K, Horie N, Furugori K, Sauchi Y, Yokogoshi H. Relieving occupational fatigue by consumption of a beverage containing γ-amino butyric acid. J Nutr Sci Vitaminol (Tokyo). 2011;57(1):9-15. 

7. Van Cauter E, Plat L. Physiology of growth hormone secretion during sleep. J Pediatr. 1996 May;128(5 Pt 2): 32-37. 

8. Maya Sakashita, Utano Nakamura, Noriko Horie, Yasuhiro Yokoyama, Mujo Kim, Satoshi Fujita. Oral Supplementation Using Gamma-Aminobutyric Acid and Whey Protein Improves Whole Body Fat-Free Mass in Men After Resistance Training J Clin Med Res. 2019 Jun; 11 (6): 428–434. 

9. Powers ME, Yarrow JF, McCoy SC, Borst SE. Growth hormone isoform responses to GABA ingestion at rest and after exercise. Med Sci Sports Exerc. 2008 Jan; 40 (1): 104-10. 

10. Jung-Ick Byun, Yu Yong Shin, Sung-Eun Chung, Won Chul Shin. Safety and Efficacy of Gamma-Aminobutyric Acid from Fermented Rice Germ in Patients with Insomnia Symptoms: A Randomized, Double-Blind Trial J Clin Neurol. 2018 Jul; 14 (3): 291–295. 

11. Cavagnini F, Invitti C, Pinto M, Maraschini C, Di Landro A, Dubini A, Marelli A. Effect of acute and repeated administration of gamma aminobutyric acid (GABA) on growth hormone and prolactin secretion in man. Acta Endocrinol (Copenh). 1980 Feb; 93 (2): 149-54. 

12. Anouk Marsman, René C. W. Mandl, Dennis W. J. Klomp, Wiepke Cahn, René S. Kahn, Peter R. Luijten, Hilleke E. Hulshoff Pol Intelligence and Brain Efficiency: Investigating the Association between Working Memory Performance, Glutamate, and GABA Front Psychiatry. 2017; 8: 154. 

13. Steenbergen L, Sellaro R, Stock AK, Beste C, Colzato LS. γ-Aminobutyric acid (GABA) administration improves action selection processes: a randomised controlled trial. Sci Rep. 2015 Jul 31; 5: 12770. 

14. Olga A. Sergeeva, Olaf Kletke, Andrea Kragler, Anja Poppek, Wiebke Fleischer, Stephan R. Schubring, Boris Görg, Helmut L. Haas, Xin-Ran Zhu, Hermann Lübbert, Günter Gisselmann, Hanns Hatt Fragrant Dioxane Derivatives Identify β1-Subunit-containing GABAA Receptors J Biol Chem. 2010 Jul 30; 285 (31): 23985–23993. 

15. Lin HC, Mao SC, Gean PW. Block of gamma-aminobutyric acid-A receptor insertion in the amygdala impairs extinction of conditioned fear. Biol Psychiatry. 2009 Oct 1; 66 (7): 665-73. 

16. Yoto A, Murao S, Motoki M, Yokoyama Y, Horie N, Takeshima K, Masuda K, Kim M, Yokogoshi H. Oral intake of γ-aminobutyric acid affects mood and activities of central nervous system during stressed condition induced by mental tasks. Amino Acids. 2012 Sep; 43 (3): 1331-7