Amino AcidsL-Theanine

Combined GABA and L-theanine supplementation improves sleep quality in adults with sleep problems

A 4-week single-arm study of 19 adults with sleep problems found that combined intake of 700 mg/day GABA and 200 mg/day L-theanine significantly improved total PSQI score from 9.42 to 6.26 (mean difference -3.15, 95% CI -4.01 to -2.31, p < 0.001). Sleep recovery scores and heart rate during sleep also showed significant improvements.

Last updated: Aug 26, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score32/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Effects of combined GABA and L-theanine supplementation on sleep quality: an exploratory study.

observational

Konno H, Naganuma K, Kamada Y · European review for medical and pharmacological sciences (2026)

Participants: N/A
Duration: 4 weeks
Intervention: Combined oral supplementation of GABA (700 mg/day) and L-theanine (200 mg/day) for 4 weeks
Outcome: Sleep quality measured by Pittsburgh Sleep Quality Index (PSQI) total score, sleep recovery score (25-point score from heart rate and turning over), and heart rate during sleep
Effect Size: N/A
Population: Adults with sleep problems (self-reported or diagnosed, not further specified)

Result:

PubMed: 41636292DOI: 10.26355/eurrev_202601_37647

Mechanism Graph

GABA acts as an inhibitory neurotransmitter to promote relaxation
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L-theanine increases alpha brain waves and reduces stress
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Combined intake may synergistically enhance sleep-promoting effects
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Result: Improved subjective and objective sleep quality metrics

Limitations

  • ⚠Single-arm design without placebo control group limits causal inference
  • ⚠Small sample size (n=19) reduces generalizability and statistical power
  • ⚠Exploratory nature of the study requires confirmation by randomized controlled trials

Frequently Asked Questions

What doses of GABA and L-theanine were used in this study?▼

The study used 700 mg/day of GABA and 200 mg/day of L-theanine, taken simultaneously for 4 weeks.

How was sleep quality measured in this study?▼

Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI) and Fitbit Charge 5 data, including sleep recovery scores and heart rate during sleep.

Did the combined supplement significantly improve sleep?▼

Yes, the total PSQI score improved significantly from 9.42 to 6.26 (mean difference -3.15, p < 0.001), and sleep recovery scores also improved significantly (p = 0.042).

Is this study conclusive for recommending GABA and L-theanine for sleep?▼

No, this is an exploratory single-arm study. The authors state that further randomized controlled trials are needed to confirm the findings.

Products

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References

  1. 1.Konno H, Naganuma K, Kamada Y. "Effects of combined GABA and L-theanine supplementation on sleep quality: an exploratory study.." European review for medical and pharmacological sciences, 2026. PMID: 41636292 DOI: 10.26355/eurrev_202601_37647
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.