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GABA and sleep quality: grade C

Limited evidence. Direction: No effect.

C LimitedShort-term only

Educational guidance, not medical advice

Why this grade

Rubric condition met: Mixed small RCTs; not N under the rubric (no adequately sized null trial on a primary sleep-quality outcome)

In a 90-day trial of 30 sedentary women with overweight or obesity, the GABA group (200 mg a day) showed better habitual sleep efficiency on the Pittsburgh Sleep Quality Index; the abstract gives no comparison with placebo. In the supplier-funded 75 mg insomnia trial, questionnaire scores improved in both the GABA and placebo groups, and in the 300 mg trial a group-by-time interaction was found only for sleep latency. In 52 adults with prediabetes taking 500 mg three times a day for 95 days, self-reported sleep quality was a secondary outcome and showed no significant effect after correction for multiple testing. The direction is mixed, so the proposal is C with direction none.

How we grade evidence

Studies this grade rests on

EffectMixedNo effectSize shows participants (n)201520202025Meta-analysisRCTYoon 2022, 2022: RCT, n = 54, result not recordedEffects of γ-aminobutyric acid 2023, 2023: RCT, n = 52, result not recordedByun 2018, 2018: RCT, n = 40, result not recordedGuimar 2024, 2024: RCT, n = 30, result not recordedHepsomali 2020, 2020: meta-analysis, n not recorded, result not recorded
each study this grade rests on, by publication year and design. Solid: effect versus the comparator; half-filled: mixed; hollow: no effect; dashed: result not recorded yet. Larger marks had more participants.
Show the numbers
StudyYearDesignParticipantsResult
Byun 20182018RCT40result not recorded
Hepsomali 20202020meta-analysisnot recordedresult not recorded
Yoon 20222022RCT54result not recorded
Effects of γ-aminobutyric acid 20232023RCT52result not recorded
Guimar 20242024RCT30result not recorded

Effects of γ-aminobutyric acid supplementation on glucose control in adults with prediabetes: A double-blind, randomized, placebo-controlled trial.

de Bie TH, Witkamp RF, Balvers MG. Effects of γ-aminobutyric acid supplementation on glucose control in adults with prediabetes: A double-blind, randomized, placebo-controlled trial Am J Clin Nutr, 2023. PMID 37495019

Result not recorded
Design
Randomized, double-blind, placebo-controlled, parallel-arm trial
Sample
n = 52
Population
Adults aged 50 to 70 with prediabetes (clinical population)
Funding
Topsector Agri & Food; Dutch Ministry of Economic Affairs (Crossref funder list)

GABA Supplementation, Increased Heart-Rate Variability, Emotional Response, Sleep Efficiency and Reduced Depression in Sedentary Overweight Women Undergoing Physical Exercise: Placebo-Controlled, Randomized Clinical Trial.

Guimarães AP, Seidel H, Pires LVM. GABA Supplementation, Increased Heart-Rate Variability, Emotional Response, Sleep Efficiency and Reduced Depression in Sedentary Overweight Women Undergoing Physical Exercise: Placebo-Controlled, Randomized Clinical Trial J Diet Suppl, 2024. PMID 38321713

Result not recorded
Design
Randomized, double-blind, placebo-controlled trial
Sample
n = 30
Population
Sedentary women with overweight or obesity taking part in an exercise program
Funding
not stated in the PubMed or Crossref record; full text not read

Efficacy and Safety of Low-Dose Gamma-Aminobutyric Acid From Unpolished Rice Germ as a Health Functional Food for Promoting Sleep: A Randomized, Double-Blind, Placebo-Controlled Trial.

Yoon S, Byun JI, Shin WC. Efficacy and Safety of Low-Dose Gamma-Aminobutyric Acid From Unpolished Rice Germ as a Health Functional Food for Promoting Sleep: A Randomized, Double-Blind, Placebo-Controlled Trial J Clin Neurol, 2022. PMID 35796273

Result not recorded
Design
Randomized, double-blind, placebo-controlled trial (letter)
Sample
n = 54
Population
Adults with insomnia (clinical population)
Funding
Natural Way Co., Ltd, which supplied the GABA

Safety and Efficacy of Gamma-Aminobutyric Acid from Fermented Rice Germ in Patients with Insomnia Symptoms: A Randomized, Double-Blind Trial.

Byun JI, Shin YY, Chung SE. 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. PMID 29856155

Result not recorded
Design
Randomized, double-blind, placebo-controlled trial (3:1 allocation)
Sample
n = 40
Population
Adults with insomnia symptoms (clinical population)
Funding
Natural Way Co. Ltd, which supplied the GABA

Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review.

Hepsomali P, Groeger JA, Nishihira J. Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review Front Neurosci, 2020. PMID 33041752

Result not recorded
Design
Systematic review of 14 placebo-controlled human trials (no meta-analysis)
Population
Healthy adults and poor sleepers in trials of natural or fermentation-produced oral GABA
Funding
Unilever UK Central Resources Limited paid open-access fees; first author employed by Unilever

Search and history

Search (): (gaba[ti] OR aminobutyric[ti]) AND (insomnia[tiab] OR sleep quality[tiab] OR polysomnograph*[tiab]) AND oral[tiab]

  • Graded C (proposed): Proposed in the monograph draft
  • C to C (approved): Editor sign-off November 13, 2026: grade matches the editor-approved final page