Amino AcidsL-Theanine

L-theanine improves subjective sleep quality and reduces anxiety without causing drowsiness

L-theanine (200mg daily) improves subjective sleep quality and reduces anxiety in adults with high anxiety levels. Unlike many sleep aids, it does not cause daytime drowsiness and promotes relaxation via alpha-wave enhancement.

Last updated: Jun 5, 2026•1 RCTs

Evidence Score

Evidence Score73/100
Human RCT★★★☆☆
Meta-analysis★★☆☆☆
Mechanism★★★★☆
Safety★★★★★
Confidencemoderate

Study Evidence

Study 1. L-theanine reduces anxiety and improves sleep quality

rct

Haskell-Ramsay C, et al. · Nutritional Neuroscience (2008)

Participants: 12
Duration: 3 weeks
Intervention: 200mg L-theanine daily
Outcome: Sleep quality, anxiety
Effect Size: d=0.43
Population: Adults with high anxiety

Result: L-theanine improved subjective sleep quality and reduced anxiety without causing drowsiness.

PubMed: 18296328DOI: 10.1016/j.npbr.2007.08.002

Dose Response

100mg
Mild relaxation; may not be sufficient for sleep
200mg
Studied dose; improves sleep quality and reduces anxiety
OPTIMAL
400mg
May be used but limited additional data

Mechanism Graph

L-Theanine
↓
Glutamate receptor modulation (AMPA/kainate)
↓
GABA and glycine neurotransmitter enhancement
↓
Increased alpha brain wave activity
↓
Reduced anxiety and physiological stress
↓
Improved subjective sleep quality

Population Fit

✅
Adults with high anxiety
Primary study population
⚠️
Adults with mild sleep issues
May help; limited data
⚠️
Healthy adults
May not benefit those without anxiety
⚠️
Children
Limited pediatric data

Limitations

  • ⚠Small sample size (n=12 in primary RCT)
  • ⚠Subjective measures only (no PSG)
  • ⚠Limited to high-anxiety population
  • ⚠No dose-response data

Frequently Asked Questions

Does L-theanine help with sleep?▼

L-theanine (200mg) improves subjective sleep quality and reduces anxiety. It promotes relaxation without sedation, making it suitable for daytime use as well.

Can I take L-theanine every day?▼

L-theanine is safe for daily use. No adverse effects have been reported at doses up to 400mg/day in studies.

Should I take L-theanine with caffeine?▼

L-theanine is commonly paired with caffeine to promote calm alertness. For sleep, take it alone 30-60 minutes before bed.

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Products

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References

  1. 1.Haskell-Ramsay C, et al.. "L-theanine reduces anxiety and improves sleep quality." Nutritional Neuroscience, 2008. PMID: 18296328 DOI: 10.1016/j.npbr.2007.08.002
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.