Supplement
GABA (Gamma-Aminobutyric Acid)
Sleep quality, mood and heart-rate variability in one 90-day trial of 30 overweight women starting an exercise program; a 2020 systematic review A review that searches for every study on a question using a method set in advance, then assesses them together. rates the evidence for stress limited and for sleep very limited; whether oral GABA reaches the brain is disputed.
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
GABA is a calming chemical in the brain, also sold as a pill. In one 90-day study of 30 women starting an exercise program, GABA was linked to better sleep and mood. A review rated the evidence for stress as limited and for sleep as very limited.
- Dose studied
- 200 mg/day
- Form graded
- Pharma-GABA / synthetic GABA
- Cited PMIDs PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed.
- PMID 38321713 →
A letter describes the human evidence, not the product, the manufacturer, or the ingredient's worth.
See the full evidence record →Who responds: this record's trial reading reports no subgroup that identifies who responds.
Sleep quality, mood and heart-rate variability on small trials, self-reported and surrogate measures.
How this letter has changed · latest: October 2026 · Corrected
The ref said Guimarães 2024 (PMID 38321713) affected stress measures; its abstract reports sleep quality, negative affect, depression scores and heart-rate variability, with no stress result, in 30 overweight women who were also starting an exercise program, and the record now says so. Added: Hepsomali 2020 (PMID 33041752), the systematic review of 14 placebo-controlled trials that rates the stress evidence limited and the sleep evidence very limited; Byun 2018 (PMID 29856155), the one trial with polysomnography, reporting within-group change only. Letter unchanged.PMID 38321713 PMID 33041752 PMID 29856155
Every change to a letter on this site is dated and published. The full evidence log →
Commercial disclosure
EBL earns no commission on any supplement it grades. A purchase made through the dispensary link below pays EBL nothing, the practitioner discount goes to you in full. The dispensary is Fullscript, a practitioner dispensary, and many of the professional-grade brands in it are sold mainly through practitioners rather than in health food stores. Grades are assigned by published rubric before any commercial relationship exists and are never influenced by one. Full disclosure.
No dose is published here. This record carries no authored dose, because the cited trials do not converge on a single figure. Each trial cited on this page states the dose it used, and EBL has not turned those into a recommendation.
Standardized extracts/forms were used in the cited trials; product quality varies.
The cited trial gave 200 mg once daily (PMID 38321713). Its summary does not state a time of day.
Checked against the published summary; the full paper could not be read. What the cited trials did, not a schedule. Every supplement, by trial timing →
Pregnancy. Anyone already sedated by medication.
Sedatives, benzodiazepines, alcohol and antihypertensives: additive effect is the concern. It is worth stating the limit of that concern, because oral GABA crosses the blood-brain barrier poorly and how much of any effect is central at all remains unsettled.
The limit the record puts on its own warning is the documented part. The record warns about additive sedation with sedatives, benzodiazepines and alcohol, then says the concern is limited because oral GABA crosses the blood-brain barrier poorly and how much of any effect is central remains unsettled. That second half is the part with human evidence behind it. A systematic review of oral GABA administration in humans found the trials on stress and sleep to be mixed, small, and frequently confounded by co-administered ingredients, with no established central mechanism for orally administered GABA. No study has given oral GABA together with a sedative drug, so the additive concern remains pharmacological reasoning about a compound whose central effects are themselves unproven. Hepsomali et al. (Front Neurosci, 2020;14:923; PMID 33041752): systematic review of the effects of oral gamma-aminobutyric acid administration on stress and sleep in humans.
Sleep onset latency and subjective sleep quality using the PSQI at baseline and 4 weeks. For anxiety, use the GAD-7 at baseline and 4 weeks. The mechanism of oral GABA's central effects is debated: both objective sleep metrics (wearable) and subjective reports, which together show whether a response is occurring.
Primary evidenceThree papers, each linked to its PubMed record.
Guimarães et al. (J Diet Suppl, 2024; PMID 38321713): randomized double-blind placebo-controlled trial, 30 sedentary women with overweight or obesity who were also starting an exercise program, 200 mg/day for 90 days; Pittsburgh Sleep Quality Index, negative affect and DASS-21 depression scores improved and heart-rate variability rose; the abstract reports no stress result. Hepsomali et al. (Front Neurosci, 2020; PMID 33041752): systematic review of 14 placebo-controlled trials of natural or biosynthetic oral GABA; limited evidence for stress and very limited evidence for sleep; first author at a consumer-goods company's research arm. Byun et al. (J Clin Neurol, 2018; PMID 29856155): the one polysomnography trial, 40 adults with insomnia symptoms randomized 3:1 to 300 mg/day rice-germ GABA or placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received. for 4 weeks; sleep latency fell and sleep efficiency rose within the GABA group, with the abstract reporting within-group change rather than a between-group difference. Grade C: small trials on self-report and surrogate endpoints A lab value or measurement used in place of the outcome that matters, such as LDL cholesterol standing in for heart attacks. Moving a surrogate does not always move the outcome., with the only objective-outcome trial reporting within-group change; oral GABA's passage into the brain is debated.
Educational use only · Not medical advice · Starting, stopping or changing any supplement or medication is a decision for your physician
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. The grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
This page carries a letter. EBL takes no commission, referral fee or payment of any kind on anything it grades. No letter has been bought and none is for sale.
How this is enforced
That is not a promise, it is a build condition. Two checks run on every deploy: one refuses to publish if a commission is claimed on anything graded, the other refuses if a page names a commercial relationship that is not declared in the register. If either fails, this page does not go live. You can read how the checks work, and what they do not cover, on the evidence integrity page.
How EBL searched for the trials (1 search)
The search that was run, what it returned, and what was left out and why, so the absence of evidence can be checked as well as its presence.
("gamma-aminobutyric acid"[tiab] OR GABA[tiab]) AND (supplement*[tiab] OR oral[tiab]) AND (stress[tiab] OR sleep[tiab]) AND (randomized controlled trial[pt] OR systematic review[pt])Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →