ANSWER

Gamma-aminobutyric acid (GABA) is a non-proteinogenic amino acid and is the main inhibitory neurotransmitter in the mammalian brain³. As an inhibitory neurotransmitter, it takes part in anxiety and stress regulation, circadian rhythm and sleep regulation, memory enhancement, mood, and even perception of pain^2,8. Data showed no serious adverse events associated with GABA at intakes up to 18 g/d for 4 days and in longer studies at intakes of 120 mg/d for 12 weeks⁷.

Based on the clinical research, the efficacious doses are³:-

1. Sleep benefits – 100-300 mg (biosynthetic GABA)
2. Stress benefits – 20-100 mg (biosynthetic GABA) or 2.01-26.4 mg (natural GABA)

Authors	Methodology	Outcomes & Findings
Hinton et al., 2019	Participants: 30 (11 males, 19 females, age range: 18–30, healthy) Intervention group: 2.01 mg GABA in 200 ml GABA Oolong Tea Control group: 0.25 mg GABA in 200 ml Oolong Tea Duration of intervention: Single dose	Autonomic imbalance and heart rate variability (HRV) in people with acute stress is significantly reduced following a cup of GABA fortified oolong tea. In humans the minimum effective oral dose of GABA leading to HRV changes was suggested at 20–30 mg (Nakamura et al., 2009). However, in this study the concentration is much lower, this reduction may due to the experimental condition or other bioactive constituents in the tea.
Byun et al., 2018	Participants: 40 (10 males, age range: 30–64, poor sleepers: PSQI >5 and ISI >8) Intervention group: Fermented rice germ extract (RFE-GABA) containing 300 mg GABA + maltodextrin (tablet) Control group: Maltodextrin (tablet) Duration of intervention: 4 weeks	Sleep latency was significantly reduced for RFE-GABA intake compared to control group. RFE-GABA intake also improved subjective sleep quality and reduced the symptom severity in subjects with insomnia. This study suggests that patients who suffer from insomnia can benefit from RFE-GABA intake without suffering severe adverse events.
Yamatsu et al., 2016	Participants: 10 (6 males, 4 females), age range: 24–57, poor sleepers: PSQI >6) Intervention group: 112mg GABA powder (100 mg GABA + 4.7 mg Glutamic acid, 2.3 mg other amino acids, 3.4 mg minerals and 1.6 mg water Control group: 112 mg dextrin	GABA significantly shortened sleep latency and increased the total non-rapid eye movement (non-REM) sleep time.
Yamatsu et al., 2015a	Participants: 16 (7 males, and 9 females), age range: 27–45, poor sleepers: PSQI >6) Participants took 2 gelatin capsules containing: – Intervention Group 1: 100mg GABA + 50mg dextrin Intervention Group 2: 50mg AVLE + 100mg dextrin Intervention Group 3: 100mg GABA + 50 mg AVLE Control: 150mg dextrin Duration of intervention: 1 week	Oral administration of 100mg GABA and 50mg Apocynum venetum leaf extract (AVLE) had beneficial effects on sleep. GABA shorted sleep latency by 5.3 min and AVLE increased non-rapid eye movement (REM) sleep time by 7.6% Simultaneous intake of GABA and AVLE shortened sleep latency by 4.3 min and increased non-REM sleep time by 5.1% GABA can help people to fall asleep quickly Safe and appropriate for daily intake to improve the quality of sleep
Yamatsu et al., 2015b	Participants: 19 (males only, age range: 24–45, healthy) Group 1: 20 mg GABA + 280 ml coffee Group 2: 280 ml coffee Control group: 280 ml water Duration of intervention: Single dose	GABA exhibited its stress-reducing and fatigue-relieving effect even in coffee. Coffee itself also showed stress-reducing effect, and the effects of coffee was enhanced by the addition of GABA.
Yoshida et al., 2015	Participants: 39 (19 males, age range: 45–60, healthy) Intervention group: 16.8 mg GABA in 150 g GABA rice/day Control group: 4.1 mg GABA in 150 g white rice/day Duration of intervention: 8 weeks	The mental condition and quality of sleep tended to improve by the intake of GABA rice. In addition, blood cortisol and adiponectin levels indicated that stress load tended to be lighten by GABA rice. In conclusion, the intake of GABA rice is effective for gently lightening the stress load.
Yamatsu et al., 2013	Participants: 38 (14 males, age range: 71–92, healthy) Intervention group: 100 mg GABA in 6.8 g chocolate Control group: Dextrin in 6.8 g chocolate Duration of intervention: 4 weeks	GABA has an effect of easing stress, improving quality of sleep, and decreasing frequency of night urination of elderly people
Yoto et al., 2011	Participants: 63 (28 males, age range: 20–28, healthy) Intervention group: 100 mg GABA (capsule) Control group: 100 mg dextrin (capsule) Duration of intervention: Single dose	GABA alleviated the stress induced by the mental tasks. This effect also corresponded with the results of the Profile of Mood States (POMS) scores.
Kanehira et al., 2011	Participants: 30 (16 males, age range: 24–43, healthy with chronic fatigue) Intervention Group 1: 25 mg GABA + 250 ml hypotonic beverage Intervention Group 2: 50 mg GABA + 250 ml hypotonic beverage Control group: 250 ml hypotonic beverage Duration of intervention: Single dose	The results suggest the intake of GABA-containing beverages, especially those containing 50mg of GABA, may help reduce both psychological and physical fatigue and improve task-solving ability.
Nakamura et al., 2009	Intervention group: 28 mg GABA in 10 g chocolate Control group: 20 g chocolate Duration of intervention: Single dose Experiment 1 (Stress-reducing effect of the GABA chocolate measured by HRV) Participants: 12 (males only, age range: 30–41, healthy) Experiment 2 Stress-reducing effect of GABA chocolate measured by salivary CgA Participants: 12 (males only, mean age: 31–42, healthy)	It is suggested that the GABA chocolate has a psychological stress-reducing effect through not only HRV changes but also salivary CgA changes.

 

 

References

¹Byun, J., Shin, Y., Chung, S., & Shin, W. (2018). Safety and Efficacy of Gamma-Aminobutyric Acid from Fermented Rice Germ in Patients with Insomnia Symptoms: A Randomized, Double-Blind Trial. Journal Of Clinical Neurology, 14(3), 291. https://doi.org/10.3988/jcn.2018.14.3.291

²Diana, M., Quílez, J., & Rafecas, M. (2014). Gamma-aminobutyric acid as a bioactive compound in foods: a review. Journal Of Functional Foods, 10, 407-420. https://doi.org/10.1016/j.jff.2014.07.004

³Hepsomali, P., Groeger, J., Nishihira, J., & Scholey, A. (2020). Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Frontiers In Neuroscience, 14, 923. https://doi.org/10.3389/fnins.2020.00923

⁴Hinton, T., Jelinek, H., Viengkhou, V., Johnston, G., & Matthews, S. (2019). Effect of GABA-Fortified Oolong Tea on Reducing Stress in a University Student Cohort. Frontiers In Nutrition, 6. https://doi.org/10.3389/fnut.2019.00027

⁵Kanehira, T., Nakamura, Y., Nakamura, K., Horie, K., Horie, N., & Furugori, K. et al. (2011). Relieving Occupational Fatigue by Consumption of a Beverage Containing γ-Amino Butyric Acid. Journal Of Nutritional Science And Vitaminology, 57(1), 9-15. https://doi.org/10.3177/jnsv.57.9

⁶Nakamura, H., Takishima, T., Kometani, T., & Yokogoshi, H. (2009). Psychological stress-reducing effect of chocolate enriched with γ-aminobutyric acid (GABA) in humans: assessment of stress using heart rate variability and salivary chromogranin A. International Journal Of Food Sciences And Nutrition, 60(sup5), 106-113. https://doi.org/10.1080/09637480802558508

⁷Oketch-Rabah, H., Madden, E., Roe, A., & Betz, J. (2021). United States Pharmacopeia (USP) Safety Review of Gamma-Aminobutyric Acid (GABA). Nutrients, 13(8), 2742. https://doi.org/10.3390/nu13082742

⁸Rashmi, D., Zanan, R., John, S., Khandagale, K., & Nadaf, A. (2018). γ-Aminobutyric Acid (GABA): Biosynthesis, Role, Commercial Production, and Applications. Studies In Natural Products Chemistry, 57, 413-452. https://doi.org/10.1016/b978-0-444-64057-4.00013-2

⁹Yamatsu A., Yamashita Y., Horie K., Takeshima K., Horie N., Masuda K., et al. (2013). Beneficial action of GABA on sleep and frequent night urination in the elderly. Japanese pharmacology & therapeutics. 41(10), 985–988.

¹⁰Yamatsu, A., Yamashita, Y., Maru, I., Yang, J., Tatsuzaki, J., & Kim, M. (2015a). The Improvement of Sleep by Oral Intake of GABA and Apocynum venetum Leaf Extract. Journal Of Nutritional Science And Vitaminology, 61(2), 182-187. https://doi.org/10.3177/jnsv.61.182

¹¹Yamatsu, A., & et al. (2015b). The Beneficial Effects of Coffee on Stress and Fatigue can be Enhanced by the Addition of GABA ―A Randomized, Double‒blind, Placebo Controlled, Crossover‒designed Study―. Japanese pharmacology & therapeutics, 43(4), 515 – 519.

¹²Yamatsu, A., Yamashita, Y., Pandharipande, T., Maru, I., & Kim, M. (2016). Effect of oral γ-aminobutyric acid (GABA) administration on sleep and its absorption in humans. Food Science And Biotechnology, 25(2), 547-551. https://doi.org/10.1007/s10068-016-0076-9

¹³Yoshida, S., Haramoto, M., Fukuda, T., Mizuno, H., Tanaka, A., Nishimura, M., & Nishihira, J. (2015). Optimization of a <i>γ</i>-aminobutyric Acid (GABA) Enrichment Process for Hokkaido White Rice and the Effects of GABA-enriched White Rice on Stress Relief in Humans. Nippon Shokuhin Kagaku Kogaku Kaishi, 62(2), 95-103. https://doi.org/10.3136/nskkk.62.95

¹⁴Yoto, A., Murao, S., Motoki, M., Yokoyama, Y., Horie, N., & Takeshima, K. et al. (2011). Oral intake of γ-aminobutyric acid affects mood and activities of central nervous system during stressed condition induced by mental tasks. Amino Acids, 43(3), 1331-1337. https://doi.org/10.1007/s00726-011-1206-6