Amino AcidsL-Theanine

L-theanine improves sleep quality and reduces stress markers in individuals with mild to moderate sleep disturbances

This study protocol describes a randomized, double-blind, placebo-controlled trial evaluating the effects of L-theanine (100mg, 200mg, 400mg) on sleep and stress markers in 60 healthy adults aged 18-65 with mild to moderate sleep disturbances. The primary outcomes are changes in objective and subjective sleep quality parameters and secondary outcomes include biochemical, physiological, and subjective stress markers after a 14-day intervention. The trial aims to determine the optimal dose of L-theanine for improving sleep and stress.

Last updated: Aug 26, 2026•1 RCTs•📖 Read as article →

Evidence Score

Evidence Score42/100
Human RCT★★☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. The effect of green tea amino acid L-theanine formulation on markers of stress and quality of sleep (THESleep project) - a study protocol for a pilot randomised control trial.

observational

Bulman A, McKune A, Georgousopoulou E, Sergi D, Naumovski N · Contemporary clinical trials (2026)

Participants: N/A
Duration: 14 days
Intervention: L-theanine in a functional beverage sachet at doses of 100mg, 200mg, or 400mg consumed daily for 14 days
Outcome: Objective and subjective sleep quality parameters, biochemical, physiological, and subjective stress markers
Effect Size: N/A
Population: Healthy adults aged 18-65 with mild to moderate sleep disturbances

Result:

PubMed: 41991056DOI: 10.1016/j.cct.2026.108306

Mechanism Graph

L-theanine crosses the blood-brain barrier
↓
Increases alpha brain wave activity
↓
Modulates neurotransmitters like GABA and serotonin
↓
Result: Reduced stress and improved sleep quality

Limitations

  • ⚠This is a study protocol, not results; no data on actual effects are reported
  • ⚠Small sample size (n=60) may limit generalizability
  • ⚠Short intervention period (14 days) may not capture long-term effects

Frequently Asked Questions

What is L-theanine?▼

L-theanine is a non-proteinogenic amino acid found primarily in tea leaves (Camellia sinensis) and is known for potential nootropic effects.

What doses of L-theanine are being tested?▼

The study tests three doses: 100mg, 200mg, and 400mg per day in a functional beverage.

Who can participate in this study?▼

Healthy adults aged 18-65 with mild to moderate sleep disturbances are eligible.

What outcomes are being measured?▼

The study measures objective and subjective sleep quality, as well as biochemical, physiological, and subjective stress markers.

Products

Affiliate links coming soon. We only recommend products that match the doses and forms used in the cited research.

References

  1. 1.Bulman A, McKune A, Georgousopoulou E, Sergi D, Naumovski N. "The effect of green tea amino acid L-theanine formulation on markers of stress and quality of sleep (THESleep project) - a study protocol for a pilot randomised control trial.." Contemporary clinical trials, 2026. PMID: 41991056 DOI: 10.1016/j.cct.2026.108306
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.