Amino AcidsL-Theanine

L-theanine supplementation significantly improves subjective sleep quality, sleep onset latency, and daytime dysfunction.

This systematic review and meta-analysis of 19 RCTs (N=897) found that L-theanine significantly improved subjective sleep onset latency (SMD=0.15, 95% CI [0.01, 0.29], p=0.04), subjective daytime dysfunction (SMD=0.33, 95% CI [0.16, 0.49], p<0.001), and overall subjective sleep quality score (SMD=0.43, 95% CI [0.04, 0.83], p=0.03). The findings suggest potential use for managing sleep disturbances, but further research is needed on pure L-theanine and optimal dosing.

Last updated: Aug 26, 2026•0 RCTs•1 Meta-analyses•📖 Read as article →

Evidence Score

Evidence Score53/100
Human RCT☆☆☆☆☆
Meta-analysis★★★☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis.

observational

Bulman A, D'Cunha NM, Marx W, Turner M, McKune A, Naumovski N · Sleep medicine reviews (2025)

Participants: N/A
Duration: N/A (varies across included studies)
Intervention: L-theanine supplementation (various doses and durations across included studies)
Outcome: Subjective sleep onset latency, subjective daytime dysfunction, overall subjective sleep quality score (measured via validated questionnaires)
Effect Size: SMD=0.43 for overall sleep quality; SMD=0.15 for sleep onset latency; SMD=0.33 for daytime dysfunction
Population: Humans of all ages and health status (N=897 participants across 19 studies)

Result:

PubMed: 40056718DOI: 10.1016/j.smrv.2025.102076

Mechanism Graph

L-theanine crosses the blood-brain barrier
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Increases levels of GABA, serotonin, and dopamine
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Promotes alpha brain wave activity associated with relaxation
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Result: Reduced sleep onset latency and improved sleep quality

Limitations

  • ⚠Lack of studies on 'pure' L-theanine (many studies may have used combination products)
  • ⚠Insufficient data to determine adequate dose and duration for improving sleep quality

Frequently Asked Questions

What is L-theanine?▼

L-theanine is a non-proteinogenic amino acid found naturally in tea, known for its relaxing effects.

How much L-theanine should I take for sleep?▼

The abstract does not specify a recommended dose; further studies are needed to determine optimal dosing.

Is L-theanine effective for all types of sleep problems?▼

The meta-analysis showed improvements in subjective sleep onset latency, daytime dysfunction, and overall sleep quality, but more research is needed for specific populations.

Are there any side effects of L-theanine?▼

The abstract does not discuss side effects; consult a healthcare provider for safety information.

Products

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References

  1. 1.Bulman A, D'Cunha NM, Marx W, Turner M, McKune A, Naumovski N. "The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis.." Sleep medicine reviews, 2025. PMID: 40056718 DOI: 10.1016/j.smrv.2025.102076
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.