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.
This article is automatically generated from the structured evidence profile behind the claim above. Scores reflect the quality and quantity of available research, not clinical advice.
L-theanine improves sleep quality and reduces stress markers in individuals with mild to moderate sleep disturbances The current body of evidence comprises 1 study, including 1 randomized controlled trial. EvidenceHub rates the overall confidence at 42/100 (low).
The Claim
L-theanine improves sleep quality and reduces stress markers in individuals with mild to moderate sleep disturbances
This conclusion is most relevant to: Healthy adults aged 18-65 with mild to moderate sleep disturbances.
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸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) —
How It Works
The proposed biological pathway:
- ▸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
Who Might Benefit
Evidence fit by population:
- ▸Healthy adults aged 18-65 with mild to moderate sleep disturbances
Recommended Dose
N/A
Limitations & Caveats
Important context when interpreting this evidence:
- ▸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.
References
- 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