Implementation Blueprint
Goal alignment: Focus, Sleep, Stress Resilience.[542,690,914, etc.]
Category
Amino Acid
Evidence Tier
HIGH
Daily Guide
100-400 mg/day
Supplement
Promotes relaxed alertness through neurotransmitter modulation.[1705,3455,3981, etc.]
Superscript reference numbers link to the Sources bibliography.
Composite Rating
Blends evidence depth, community direction, safety friction, and completeness.
Evidence Intensity
100/100
High depth from human/RCT/meta counts
Community Direction
18
Positive Lean • confidence Minimal
Safety Friction
100/100
High signal from adverse/interaction markers
Data Completeness
100%
Studies 12 • mentions 4 • links 22
Not medical advice. This product is for educational and informational purposes only. It does not diagnose, treat, cure, or prevent any disease and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.
FDA disclaimer: These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Results may vary. Not intended for use by pregnant or nursing women, individuals under 18, or those with known medical conditions without physician consultation.
If you are experiencing a medical emergency, call 911 or your local emergency number immediately.
Goal alignment: Focus, Sleep, Stress Resilience.[542,690,914, etc.]
Category
Amino Acid
Evidence Tier
HIGH
Daily Guide
100-400 mg/day
Clinical Depth
Humans: 91 • RCTs: 32 • Meta: 2
Cohort / Real-World
Cohort signals: 0
Safety Markers
Adverse signals: 69 • Interactions: 90
Freshness, trend, and study timeline for this item
Status
Trend
↑ Growing evidence base
Depth
198 total studies · 3 recent
Timeline
Animal-only studies
254
Total indexed
198
In vitro / tissue
105
Human studies
91
Interaction signals
90
Safety adverse signals
69
Weighted direction score: 18 (Positive Lean)
High when >=2 human meta-analyses, or >=5 human RCTs with substantial human literature volume.
Animal-only studies
254
Total indexed
198
In vitro / tissue
105
Human studies
91
Interaction signals
90
Safety adverse signals
69
Randomized trials
32
Meta-analyses
2
Distribution of evidence by study design strength
Evidence Strength: High
Composite of study volume, RCTs, and meta-analyses
PMID 40314930 • 2025 Oct 1
Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Nutr Rev
Open PubMedPMID 40056718 • 2025 Jun
The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis.
Sleep Med Rev
Open PubMedPMID 39213264 • 2024
Effect of matcha green tea on cognitive functions and sleep quality in older adults with cognitive decline: A randomized controlled study over 12 months.
Benefit reports: 2
Adverse reports: 1
No-effect reports: 0
Mixed reports: 1
Unclear reports: 0
Signal confidence: 0.00
Benefits
Adverse
No Effect
Highly favored as caffeine co-stack. | Step2: Insufficient empirical signal for a directional adjustment.
Reddit evidence: 0 mentions (confidence 0.00).
Amazon signal: 0 products scanned (confidence 0.00).
aggregate • benefit
Aggregate community signal: 4 directional mentions (benefit 2, adverse 1, no-effect 0, mixed 1).
Open mentionamazon
Amazon search for L-Theanine
Rating: n/a | Reviews: n/a
Open productEvidence Sources
RCT • 2020 • Adults
Adults with mild stress.
Outcome: Reduces perceived stress and improves attention in some trials.[1705,3455,3981, etc.]
PUBMED • Humans + preclinical triage
Counts aggregated from automated literature sweep and tiering rules.
Outcome: Tier HIGH; humans 91, RCTs 32, meta-analyses 2.[1705,3455,3981, etc.]
Open sourcePLoS One
PMID 36094342 • 2023 Feb 1
Nutritional Modulation of Sleep Latency, Duration, and Efficiency: A Randomized, Repeated-Measures, Double-Blind Deception Study.
Med Sci Sports Exerc
Open PubMedPMID 16930802 • 2007 Jan
L-Theanine reduces psychological and physiological stress responses.
Biol Psychol
Open PubMedPMID 33751906 • 2021 Apr
Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study.
J Med Food
Open PubMedPMID 35215501 • 2022 Feb 18
Use of Nutritional Supplements Based on L-Theanine and Vitamin B6 in Children with Tourette Syndrome, with Anxiety Disorders: A Pilot Study.
Nutrients
Open PubMedPMID 37815006 • 2023 Dec
Effect of single or combined caffeine and L-Theanine supplementation on shooting and cognitive performance in elite curling athletes: a double-blind, placebo-controlled study.
J Int Soc Sports Nutr
Open PubMedPMID 36862943 • 2023 Dec
International society of sports nutrition position stand: energy drinks and energy shots.
J Int Soc Sports Nutr
Open PubMedPMID 37603263 • 2023 Sep
Over the Counter Supplements for Memory: A Review of Available Evidence.
CNS Drugs
Open PubMedPMID 37175525 • 2023 Apr 25
The Role of Supplements and Over-the-Counter Products to Improve Sleep in Children: A Systematic Review.
Int J Mol Sci
Open PubMedPMID 31758301 • 2020 Mar
The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.
Plant Foods Hum Nutr
Open PubMedGNC signal: 0 products scanned (confidence 0.00) [BLOCKED].
PerimeterX / captcha block encountered.
Search fetch failed: Failed to fetch after retries: https://old.reddit.com/search.json?raw_json=1&sort=relevance&t=year&limit=12&q=%22l-theanine%22%20(supplement%20OR%20dosage%20OR%20stack%20OR%20side%20effects%20OR%20review)%20(subreddit%3ASupplements%20OR%20subreddit%3ANootropics%20OR%20subreddit%3ABiohackers%20OR%20subreddit%3Alongevity%20OR%20subreddit%3ANutrition%20OR%20subreddit%3AHubermanLab%20OR%20subreddit%3ASleep%20OR%20subreddit%3AFitness%20OR%20subreddit%3Aketoscience%20OR%20subreddit%3AStackAdvice)
Fallback search failed: Failed to fetch after retries: https://old.reddit.com/search.json?raw_json=1&sort=comments&t=all&limit=16&q=%22l-theanine%22%20(supplement%20OR%20capsule%20OR%20powder%20OR%20experience%20OR%20results%20OR%20side%20effects)
Broad search failed: Failed to fetch after retries: https://old.reddit.com/search.json?raw_json=1&sort=new&t=all&limit=16&q=l-theanine
Use adverse/interactions PubMed signal counts for screening; perform clinician review before high-dose or multi-drug stack use.
Imported legacy community score: 9.0/10 (heuristic mapping confidence 1.00).
Imported legacy monthly cost signal: ~$12.00.
Legacy community note: One of the most beloved supplements in nootropic and anxiety communities. "Caffeine + L-theanine" is considered the foundational nootropic stack. Users describe it as "calm focus" and "anxiety without the edge."
Community Sources
PUBMED • 2025 • Human evidence curation set
PMID 40314930 from Nutr Rev.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2025 • Human evidence curation set
PMID 40056718 from Sleep Med Rev.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2024 • Human evidence curation set
PMID 39213264 from PLoS One.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2023 • Human evidence curation set
PMID 36094342 from Med Sci Sports Exerc.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2007 • Human evidence curation set
PMID 16930802 from Biol Psychol.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2021 • Human evidence curation set
PMID 33751906 from J Med Food.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2022 • Human evidence curation set
PMID 35215501 from Nutrients.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2023 • Human evidence curation set
PMID 37815006 from J Int Soc Sports Nutr.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2023 • Human evidence curation set
PMID 36862943 from J Int Soc Sports Nutr.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2023 • Human evidence curation set
PMID 37603263 from CNS Drugs.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2023 • Human evidence curation set
PMID 37175525 from Int J Mol Sci.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open sourcePUBMED • 2020 • Human evidence curation set
PMID 31758301 from Plant Foods Hum Nutr.
Outcome: See linked PubMed abstract for methods and outcomes.[1705,3455,3981, etc.]
Open source