GABA
A systematic review of 14 placebo-controlled trials found limited evidence for stress and very limited evidence for sleep. Small trials reported lower systolic blood pressure and higher growth hormone after a dose. Most trials had industry-employed authors. A USP safety review found no serious adverse events, and some studies showed modest blood pressure drops.
Add to Bio HackChecked 2026-11-09
- Status
- Dietary supplement in the US.
- Also called
- gamma-aminobutyric acid, γ-aminobutyric acid, PharmaGABA, GABA-rich foods, fermented GABA
- Taken for
- stress, anxiety, relaxation, sleep, blood pressure, growth hormone, muscle gain
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help1
Reported risks2
- LimitedOne trial found AST rose in 9 of 35 men with type 1 diabetes on a controlled-release GABA for 6 months, mostly briefly.Very common
- LimitedLimited evidence: USP reports some studies with a brief blood pressure drop under 10%, and states that blood pressure medicines could conceivably add to it.How often is not known
What people take it for, and what was found
Shown to help1
Blood pressure
One trial found GABA-rich Chlorella lowered systolic pressure more than placebo in adults with high-normal blood pressure. GABA alone was not tested.
The numbers and sources
- Effect
- In 80 adults with high-normal blood pressure or borderline hypertension, GABA-rich Chlorella (20 mg of GABA twice a day) for 12 weeks lowered systolic pressure more than placebo (p below 0.01). Diastolic pressure tended to fall [5]. A USP review found some studies with a transient, moderate drop in blood pressure of less than 10% [6].
- Population
- 80 Japanese adults [5]. Clinical studies reviewed by USP [6].
- Sources
- [5], [6]
- Caveats
- The trial tested GABA inside Chlorella, so the effect cannot be assigned to GABA alone. The abstract does not give the size of the change [5].
Mixed results3
Stress
Limited evidence: a review of 14 trials found limited support for stress outcomes, and most studies had authors from industry.
The numbers and sources
- Effect
- A systematic review of 14 placebo-controlled trials of natural or fermented GABA found limited evidence for stress outcomes [1]. In 63 adults, 100 mg of GABA 30 minutes before mental tasks reduced the task-related drop in alpha and beta brain waves compared with placebo, and mood scores matched this [2]. In 8 male university students who play esports, 200 mg of GABA before gameplay lowered confusion and fatigue mood scores and raised game task scores compared with placebo [3].
- Population
- Adults in trials of single doses to several weeks [1]. 28 men and 35 women in a single-blind crossover [2]. 8 men aged 20 to 24, crossover [3].
- Sources
- [1], [2], [3]
- Caveats
- No meta-analysis was possible because outcomes varied. In 11 of the 14 studies, one or more authors worked for an industrial company [1]. All authors of the esports trial are inventors on a related patent application filed with Pharma Foods International [3].
Sleep
Limited evidence: a review found very limited support for sleep. One trial found faster sleep onset on GABA than placebo.
The numbers and sources
- Effect
- The same review found very limited evidence for sleep [1]. In a single-blind crossover trial, GABA shortened the time to fall asleep and increased non-REM sleep on EEG compared with placebo [4].
- Population
- Adults [1][4].
- Sources
- [1], [4]
- Caveats
- The abstract of [4] does not give participant numbers or effect sizes.
Growth hormone and lean mass
Small trials found 3 g raised growth hormone in trained men, but 200 mg a day did not change body fat or lean mass in women with obesity.
The numbers and sources
- Effect
- In 11 resistance-trained men, 3 g of GABA raised peak resting growth hormone about 400% and area under the curve about 375% compared with placebo, and growth hormone was also higher after exercise [7]. In 21 men training twice a week for 12 weeks, 10 g of whey plus 100 mg of GABA increased fat-free mass more than whey alone [8]. In 26 women with obesity training 3 days a week for 90 days, 200 mg of GABA a day did not change body fat, fat mass, fat-free mass or growth hormone compared with placebo. Within the GABA group, BMI and waist circumference fell and sit-up performance rose [9].
- Population
- 11 men aged 18 to 30, crossover [7]. 21 men aged 26 to 48 [8]. 26 women with obesity [9].
- Sources
- [7], [8], [9]
- Caveats
- All three trials were small. The within-group changes in the women's trial were not differences from placebo [9]. The lean mass trial was funded by Pharma Foods International, which supplied the GABA and employed four authors [8]. A rise in growth hormone was not shown to change muscle in [7].
Doses studied
Stress and sleep trials used single or daily doses, including 100 mg before a mental task [2]. The blood pressure trial gave 20 mg of GABA twice a day in Chlorella for 12 weeks [5]. The growth hormone trial used a single 3 g dose [7], and the training trials 100 mg a day with whey for 12 weeks [8] and 200 mg a day for 90 days [9]. The USP review found studies up to 18 g a day for 4 days and 120 mg a day for 12 weeks [6].
Risks
Reported risks2
Liver enzyme rises in a 6-month trial
One trial found AST rose in 9 of 35 men with type 1 diabetes on a controlled-release GABA for 6 months, mostly briefly.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- In 35 men with long-standing type 1 diabetes given a controlled-release GABA (200 or 600 mg a day, one arm with alprazolam for 3 months) for 6 months, AST rose in 9 men and 2 withdrew. Most rises were transient, with no difference by dose. The authors report that side effects were common [10].
- Population
- 35 adult men in Sweden with type 1 diabetes for 5 years or more [10].
- Sources
- [10]
- Caveats
- All three arms received GABA, so there was no placebo comparison. It tested a pharmaceutical formulation (Remygen) in people with diabetes [10].
Blood pressure drop and blood pressure medicines
Limited evidence: USP reports some studies with a brief blood pressure drop under 10%, and states that blood pressure medicines could conceivably add to it.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Some studies showed a transient, moderate fall in blood pressure of less than 10%. The USP reviewers state that use alongside blood pressure medicines could conceivably raise the risk of low blood pressure [6].
- Population
- Clinical studies reviewed by USP [6].
- Sources
- [6]
- Caveats
- The interaction is inferred from the blood pressure findings, not observed in a study [6].
Checked, no increase found1
Adverse events in trials and reports
Limited evidence: USP found no serious adverse events in short trials and no case reports linked to GABA.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- USP found no serious adverse events at up to 18 g a day for 4 days, or at 120 mg a day for 12 weeks. It found no case reports or spontaneous adverse event reports linked to GABA [6]. The Chlorella trial reported no adverse events or abnormal lab findings over 12 weeks [5].
- Population
- Clinical studies and adverse event databases reviewed by USP [6]. 80 adults [5].
- Sources
- [5], [6]
- Caveats
- Most trials were short. USP found no studies in pregnancy or lactation, and noted that GABA can raise growth hormone and prolactin levels [6].
Sources
- Hepsomali P, Groeger JA, Nishihira J, et al. Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Frontiers in Neuroscience. 2020. https://doi.org/10.3389/fnins.2020.00923
- Yoto A, Murao S, Motoki M, et al. Oral intake of γ-aminobutyric acid affects mood and activities of central nervous system during stressed condition induced by mental tasks. Amino Acids. 2012. https://doi.org/10.1007/s00726-011-1206-6
- Hara Y, Nakamura U, Koga K, et al. γ-Aminobutyric Acid Intake Improves Psychological State and Performance in Esports: A Randomized, Placebo-Controlled, Double-Blind Crossover Study. Nutrients. 2025. https://doi.org/10.3390/nu17111870
- Yamatsu A, Yamashita Y, Pandharipande T, et al. Effect of oral γ-aminobutyric acid (GABA) administration on sleep and its absorption in humans. Food Science and Biotechnology. 2016. https://doi.org/10.1007/s10068-016-0076-9
- Shimada M, Hasegawa T, Nishimura C, et al. Anti-Hypertensive Effect of γ-Aminobutyric Acid (GABA)-Rich Chlorella on High-Normal Blood Pressure and Borderline Hypertension in Placebo-Controlled Double Blind Study. Clinical and Experimental Hypertension. 2009. https://doi.org/10.1080/10641960902977908
- Oketch-Rabah HA, Madden EF, Roe AL, et al. United States Pharmacopeia (USP) Safety Review of Gamma-Aminobutyric Acid (GABA). Nutrients. 2021. https://doi.org/10.3390/nu13082742
- Powers ME, Yarrow JF, McCoy SC, et al. Growth Hormone Isoform Responses to GABA Ingestion at Rest and after Exercise. Medicine & Science in Sports & Exercise. 2008. https://doi.org/10.1249/mss.0b013e318158b518
- Sakashita M, Nakamura U, Horie N, et al. Oral Supplementation Using Gamma-Aminobutyric Acid and Whey Protein Improves Whole Body Fat-Free Mass in Men After Resistance Training. Journal of Clinical Medicine Research. 2019. https://doi.org/10.14740/jocmr3817
- de Medeiros Pires LV, de Barros Martins A, Trindade CMO, et al. Effects of combined gamma aminobutyric acid supplementation and exercise training on the body composition of women: A randomized double-blind trial. Clinical Nutrition ESPEN. 2025. https://doi.org/10.1016/j.clnesp.2025.04.028
- Hill H, Lundkvist P, Tsatsaris G, et al. Long-term gamma-aminobutyric acid (GABA) treatment fails to regain beta-cell function in longstanding type 1 diabetes in a randomized trial. Scientific Reports. 2025. https://doi.org/10.1038/s41598-025-95751-y