Amino AcidsL-Theanine

L-theanine supplementation at 200-450 mg/day supports healthy sleep in adults

A systematic review of 13 trials (n=550) found that L-theanine at 200-450 mg/day appears safe and effective for improving sleep in adults. Beneficial effects were reported on sleep latency, maintenance, efficiency, perceived satisfaction, and feelings of refreshment upon waking.

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. Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trials.

observational

Cotter J, Caddick CE, Harper JL, Ebajemito JK · Nutritional neuroscience (2026)

Participants: N/A
Duration: N/A
Intervention: L-theanine dietary supplementation (50-900 mg/day) as a standalone intervention
Outcome: Sleep-related outcome measures including sleep latency, maintenance, efficiency, perceived sleep satisfaction, and feelings of refreshment and recovery on waking
Effect Size: N/A
Population: Adults (general population, not specifically clinical insomnia patients)

Result:

PubMed: 41176609DOI: 10.1080/1028415X.2025.2556925

Mechanism Graph

L-theanine is a non-protein amino acid from tea leaves
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Previous studies show it aids relaxation without sedation
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Pre-clinical studies suggest calming effects
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Result: Supports healthy sleep in adults

Limitations

  • ⚠Only 13 trials with small total sample size (n=550)
  • ⚠No high-quality trials specifically in clinical insomnia populations
  • ⚠Limited use of objective sleep measures in some trials

Frequently Asked Questions

What is the recommended dose of L-theanine for sleep?▼

Based on this review, 200-450 mg/day appears safe and effective for supporting healthy sleep in adults.

Does L-theanine cause sedation or affect cognitive function?▼

No, previous studies report that L-theanine aids relaxation without causing sedation or adversely impacting cognitive function.

What sleep outcomes does L-theanine improve?▼

It improves sleep latency, maintenance, efficiency, perceived sleep satisfaction, and feelings of refreshment and recovery on waking.

Is L-theanine effective for people with clinical insomnia?▼

The review did not specifically study clinical insomnia patients; further high-quality trials in that population are needed.

Products

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References

  1. 1.Cotter J, Caddick CE, Harper JL, Ebajemito JK. "Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trials.." Nutritional neuroscience, 2026. PMID: 41176609 DOI: 10.1080/1028415X.2025.2556925
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.