L-theanine supplementation improves subjective sleep quality, reduces sleep onset latency, and decreases daytime dysfunction.
A systematic review and meta-analysis of 19 RCTs (N=897 participants) 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.
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 supplementation improves subjective sleep quality, reduces sleep onset latency, and decreases daytime dysfunction. The current body of evidence comprises 1 study and 1 meta-analysis. EvidenceHub rates the overall confidence at 53/100 (low).
The Claim
L-theanine supplementation improves subjective sleep quality, reduces sleep onset latency, and decreases daytime dysfunction.
This conclusion is most relevant to: Humans of all ages and health status.
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis. (Sleep medicine reviews, 2025) —
How It Works
The proposed biological pathway:
- ▸L-theanine is a non-proteinogenic amino acid found in tea
- ▸It may promote relaxation by increasing GABA, serotonin, and dopamine levels
- ▸It reduces stress and anxiety, which can interfere with sleep
- ▸Result: Improved subjective sleep quality and reduced sleep onset latency
Who Might Benefit
Evidence fit by population:
- ▸Humans of all ages and health status
Recommended Dose
N/A (not specified in abstract; requires further investigation)
Limitations & Caveats
Important context when interpreting this evidence:
- ▸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 and where is it found?▼
L-theanine is a non-proteinogenic amino acid primarily found in tea leaves, especially green tea. It is known for its calming effects.
How does L-theanine improve sleep?▼
L-theanine may improve sleep by promoting relaxation through modulation of neurotransmitters like GABA, serotonin, and dopamine, and by reducing stress and anxiety.
What sleep outcomes did L-theanine improve in this meta-analysis?▼
The meta-analysis showed significant improvements in subjective sleep onset latency, daytime dysfunction, and overall subjective sleep quality score.
Is L-theanine safe for all populations?▼
The abstract included participants of all ages and health status, but specific safety data and optimal dosing were not provided, so caution is warranted, especially for clinical populations.
References
- 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