GABARelax® (Gamma-Aminobutyric Acid)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

1. Yamatsu A, Yamashita Y, Pandharipande T, et al. Effect of oral γ-aminobutyric acid (GABA) administration on sleep and its absorption in humans. Food Sci Biotechnol. 2016;25(2):547-551..PubMedUsed to support: In 10 adults with poor sleep quality, 100 mg of GABA taken before bed for one week shortened EEG-measured sleep latency and increased total non-REM sleep time against a dextrin placebo, in a single-blind crossover design. Deep slow-wave sleep, REM sleep time and awakening frequency did not change. Blood GABA peaked 30 minutes after dosing, but the study did not measure brain GABA. All five authors worked for Pharma Foods International, which sells a competing branded GABA, and the material tested was not GABARelax.
2. Hepsomali P, Groeger JA, Nishihira J, Scholey A Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Front Neurosci. 2020;14:923..PubMedUsed to support: Systematic review of 14 placebo-controlled human trials of oral GABA, natural and fermentation-derived. It concluded there is limited evidence for stress and very limited evidence for sleep, that most trials measured autonomic surrogates such as heart-rate variability, cortisol and chromogranin A rather than felt stress, and that no data exist showing oral GABA crosses the blood-brain barrier in humans.
3. Boonstra E, de Kleijn R, Colzato LS, Alkemade A, Forstmann BU, Nieuwenhuis S Neurotransmitters as food supplements: the effects of GABA on brain and behavior. Front Psychol. 2015;6:1520..PubMedUsed to support: Review of GABA sold as a food supplement. It reports that GABA has long been thought unable to cross the blood-brain barrier, that the studies testing this are contradictory, that no work has yet shown oral GABA raising GABA in the human brain, and that most of the positive calming evidence comes from researchers with a potential conflict of interest. The authors conclude the mechanism of action is far from clear.
4. Byun JI, Shin YY, Chung SE, Shin WC 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;14(3):291-295..PubMedUsed to support: Randomized, double-blind, placebo-controlled trial of 300 mg/day of GABA from fermented rice germ extract, taken an hour before sleep for four weeks, in 40 people with insomnia symptoms allocated 30 to GABA and 10 to placebo. Polysomnographic sleep latency was the only measure with a significant group-by-time difference, but the two arms were not comparable at baseline: the placebo group started at 7.0 minutes and worsened to 15.2, while the GABA group fell from 13.4 to 5.7. Sleep efficiency and every sleep questionnaire improved in both arms with no difference between them. Adverse events occurred in 4 of 40 participants and 2 of 40 reported drowsiness. The study was funded by the company that supplied the GABA, and the material was not GABARelax.
5. Abdou AM, Higashiguchi S, Horie K, Kim M, Hatta H, Yokogoshi H Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans. Biofactors. 2006;26(3):201-8..PubMedUsed to support: In 13 volunteers, a single 100 mg dose of GABA raised EEG alpha-wave activity and the alpha/beta ratio 60 minutes later compared with water or L-theanine; the accompanying fall in beta waves was reported as significant by the authors but extracted as a trend only by a later systematic review. Only brain-wave patterns were recorded in that experiment, with no anxiety or relaxation questionnaire, so the authors' conclusion that GABA reduces anxiety rests on the EEG pattern alone. A second experiment gave GABA to 8 acrophobic volunteers crossing a suspended bridge and measured salivary immunoglobulin A. The work was carried out by the research and development department of Pharma Foods International, a GABA manufacturer.
6. 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;43(3):1331-7..PubMedUsed to support: In 63 adults given 100 mg of GABA or dextrin in a randomized single-blind crossover, EEG alpha and beta activity fell as mental task load rose, and 30 minutes after GABA that fall was smaller than after placebo. The endpoint is an EEG pattern rather than a measured stress outcome. The authors reported that the mood questionnaire agreed with the EEG result, but the systematic review that later extracted this trial recorded its tension, anxiety, arousal and relaxation scores as not significant.
7. Oketch-Rabah HA, Madden EF, Roe AL, Betz JM United States Pharmacopeia (USP) Safety Review of Gamma-Aminobutyric Acid (GABA). Nutrients. 2021;13(8):2742..PubMedUsed to support: US Pharmacopeia safety evaluation of GABA sold as a dietary supplement. No serious adverse events were found at intakes up to 18 g/day for 4 days or 120 mg/day for 12 weeks, and no case reports or spontaneous adverse-event reports were located. Some studies recorded a transient drop in blood pressure of under 10 percent, so combining GABA with antihypertensive medication could risk hypotension. No data exist for pregnancy or lactation, and caution is advised there because GABA can raise growth hormone and prolactin.