Safety Profile
Known Safety Concerns
- May potentiate sedative medications at high doses
- Additive blood pressure lowering with antihypertensives
- No established UL -- long-term very high dose data limited
- Generally regarded as one of the safest supplement ingredients
Contraindications
- May potentiate sedative medications at high doses
- Additive blood pressure lowering with antihypertensives
Interactions
Information not yet available for this ingredient profile.
Evidence and Scientific Findings
Ingredient Overview
L-theanine is an amino acid found almost exclusively in tea leaves. It has a well-established safety profile at doses of 100-400 mg/day. It promotes relaxation without sedation and is commonly combined with caffeine to smooth its stimulant effects. No adverse effects have been documented at standard doses. No established UL.
Biological and Chemical Classification
- Scientific Name
- N5-ethyl-L-glutamine
Mechanism of Action
Information not yet available for this ingredient profile.
Clinical Evidence of Effectiveness
Information not yet available for this ingredient profile.
Pharmacokinetics
Information not yet available for this ingredient profile.
Recommended Dosage
Information not yet available for this ingredient profile.
SETI — Scientific Evidence Transparency Index
Executive Summary — Ingredient Assessment
- 10 studies reviewed
- 0 high-quality studies (meta-analysis or RCT)
- Main clinical benefit observed: Botanical
- Evidence consistency: High consistency across studies (100%)
- May potentiate sedative medications at high doses
- Additive blood pressure lowering with antihypertensives
- No established UL -- long-term very high dose data limited
- Generally regarded as one of the safest supplement ingredients
The available scientific evidence for L-Theanine indicates notable safety signals that warrant caution. Use should be considered carefully and monitored, particularly in sensitive populations or alongside other medications.
Total SETI Score
High risk| Evidence quality | 10/40 |
| Evidence consistency | 20/20 |
| Safety signals | 0/20 |
| Study recency | 10/10 |
| Evidence transparency | 10/10 |
Evidence Summary
- 10 studies reviewed
- 0 high-quality studies (meta-analysis or systematic review)
- 0 studies identified benefits or no safety concern (GREEN)
- 10 studies reported limited or advisory safety evidence (YELLOW)
Evidence Policy
Only peer-reviewed scientific literature indexed in PubMed or comparable databases is included in this evaluation. Commercial websites, blogs, and marketing materials are excluded. All references include direct traceable links to source documents.
Last updated: 23 მარ 2026, 18:47
Evidence Distribution
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Observational / other LOW evidence YELLOWBeneath the Surface: Root Metabolites Driving Shoot Agronomic Traits in Tea Plant (Camellia sinensis L.). ↗Huang Y et al.. Beneath the Surface: Root Metabolites Driving Shoot Agronomic Traits in Tea Plant (Camellia sinensis L.).. J Agric Food Chem. 2026. PMID:41848094.PMID 41848094 ↗Journal J Agric Food ChemYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41848094/
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Observational / other LOW evidence YELLOWClinical assessment of blood glucose responses to 300-mg dose of L-theanine, an amino acid unique to green tea, in a fixed-sequence, two-period… ↗Yamaura S et al.. Clinical assessment of blood glucose responses to 300-mg dose of L-theanine, an amino acid unique to green tea, in a fixed-sequence, two-period trial.. J Pharm Health Care Sci. 2026. PMID:41845544.PMID 41845544 ↗Journal J Pharm Health Care SciYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41845544/
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Observational / other LOW evidence YELLOWA microbial L-theanine-BCAT2 axis rewires host BCAA catabolism. ↗Fang X et al.. A microbial L-theanine-BCAT2 axis rewires host BCAA catabolism.. Sci China Life Sci. 2026. PMID:41840166.PMID 41840166 ↗Journal Sci China Life SciYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41840166/
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Observational / other LOW evidence YELLOWNew and emerging treatments for anxiety disorders. ↗Zbozinek TD et al.. New and emerging treatments for anxiety disorders.. BMJ. 2026. PMID:41839508.PMID 41839508 ↗Journal BMJYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41839508/
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Observational / other LOW evidence YELLOWCombined and Separate Pretreatments with L-Theanine and Aerobic Exercise Modulate Cognitive Decline Following Chronic Neuroinflammation in Rats Exposed to Lipopolysaccharide. ↗Hadzhipetrov GK et al.. Combined and Separate Pretreatments with L-Theanine and Aerobic Exercise Modulate Cognitive Decline Following Chronic Neuroinflammation in Rats Exposed to Lipopolysaccharide.. Int J Mol Sci. 2026. PMID:41828356.PMID 41828356 ↗Journal Int J Mol SciYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41828356/
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Observational / other LOW evidence YELLOWL-theanine as a sustainable feed additive: Evaluating impacts on animal health and production efficiency. ↗Wu S et al.. L-theanine as a sustainable feed additive: Evaluating impacts on animal health and production efficiency.. Microb Pathog. 2026. PMID:41802656.PMID 41802656 ↗Journal Microb PathogYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41802656/
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Observational / other LOW evidence YELLOWPharmacological effects and molecular targets of L-theanine in cardiovascular diseases and comorbidities. ↗Garcu00eda-Niu00f1o WR et al.. Pharmacological effects and molecular targets of L-theanine in cardiovascular diseases and comorbidities.. Eur J Pharmacol. 2026. PMID:41796839.PMID 41796839 ↗Journal Eur J PharmacolYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41796839/
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Observational / other LOW evidence YELLOWComparative evaluation of l-theanine synthetases coupled with PPK2 based ATP regeneration under buffer-free and Mn(2u202f+) optimized conditions. ↗Yu K et al.. Comparative evaluation of l-theanine synthetases coupled with PPK2 based ATP regeneration under buffer-free and Mn(2u202f+) optimized conditions.. Enzyme Microb Technol. 2026. PMID:41762940.PMID 41762940 ↗Journal Enzyme Microb TechnolYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41762940/
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Observational / other LOW evidence YELLOWAntidepressant Mechanisms of L-Theanine in Tea Based on Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulations. ↗Shi Y et al.. Antidepressant Mechanisms of L-Theanine in Tea Based on Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulations.. Foods. 2026. PMID:41683141.PMID 41683141 ↗Journal FoodsYear 2026Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41683141/
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Observational / other LOW evidence YELLOWKiperin Mind Focus supplement mitigates chronic stress-induced neuroinflammation and molecular dysregulation and improves stress-related affective and exploratory behaviors in rats. ↗Karcioglu Batur L et al.. Kiperin Mind Focus supplement mitigates chronic stress-induced neuroinflammation and molecular dysregulation and improves stress-related affective and exploratory behaviors in rats.. Front Integr Neurosci. 2025. PMID:41695889.PMID 41695889 ↗Journal Front Integr NeurosciYear 2025Study type Observational / otherEvidence strength LOW evidencePubMed link https://pubmed.ncbi.nlm.nih.gov/41695889/
Score Transparency
0 of 10 approved references (score saturates at 10). More peer-reviewed studies = stronger evidence base.
Method: Q = number of approved references ÷ 10 (capped at 1.0)
Limited — mostly case reports or animal studies
Method: L = mean study-level weight across approved references. Level 1 (meta-analysis / systematic review) = 1.0; Level 2 (RCT) = 0.8; Level 3 (cohort/case-control) = 0.6; Level 4 (case report) = 0.4; Level 5 (animal / in-vitro) = 0.2.
Mixed or neutral — roughly equal benefit and risk signals
Method: D = (sum of risk-scored references − sum of benefit-scored references) ÷ total evidence score, then scaled from [−1, 1] to [0, 1]. 0.0 = pure benefit; 0.5 = neutral; 1.0 = pure risk.
One or more monitoring-level safety signals active
Method: S = 0.5 (neutral baseline) + sum of active signal severity deltas ÷ 10. Severity deltas: Critical = +2.0, High = +1.5, Moderate = +1.0, Low = +0.5. Capped at 1.0.
Final GIRI Score for L-Theanine. Risk level thresholds: Low 0–3.0 · Moderate 3.0–5.5 · High 5.5–7.5 · Critical 7.5–10.
Full methodology & data sources
The GIRI Score is computed entirely from structured data — no editorial scoring or subjective weighting is applied at any step.
- References: Only approved references are counted. Each reference is assigned an evidence level (L1–L5) and a direction (risk / neutral / benefit) by the reference manager or AI classifier.
- Safety Signals: Sourced from regulatory agencies (FDA, EMA, Health Canada, TGA, and others) and pharmacovigilance databases. Only active signals count toward the score.
- Formula version: GIRI Score v3.7.0 — Q × L × D × S × 10.
- Limitations: The score reflects published evidence and recorded signals as of the last update date. It is not a clinical risk assessment and should not replace advice from a qualified healthcare professional.
Risk Level Classification
Based on available regulatory signals and scientific evidence, this ingredient presents a low safety concern under normal conditions of use.
0–3.0
3.0–5.5
5.5–7.5
7.5–10
The score pin shows exactly where this ingredient falls on the fixed risk scale.
What drove the Low classification for L-Theanine
A score of 1.5 places this ingredient in the Low band. Thresholds: Low 0–3.0 · Moderate 3.0–5.5 · High 5.5–7.5 · Critical 7.5–10.
0 approved references.
Limited — mostly case reports or animal studies (Level 4–5).
Neutral or mixed — benefit and risk signals roughly balanced.
No active signals — S component is at neutral baseline (0.5), contributing no extra risk weight.
No major regulatory restrictions or advisories recorded across monitored jurisdictions (FDA, EMA, Health Canada, TGA, and others).
How are the Low / Moderate / High / Critical thresholds defined?
The four risk levels are fixed score bands. A score is assigned to exactly one level based on where it falls:
| Level | Score | Meaning |
|---|---|---|
| LOW | 0.0 – 2.9 | Sparse or predominantly beneficial evidence. No active safety alerts. |
| MODERATE | 3.0 – 5.4 | Mixed signals — some risk alongside benefit. Caution at high doses or in sensitive groups. |
| HIGH | 5.5 – 7.4 | Multiple studies or regulatory alerts documenting adverse effects. Professional oversight recommended. |
| CRITICAL | 7.5 – 10 | Regulatory restrictions in one or more major jurisdictions. Serious documented harm. Avoid without specialist supervision. |
Thresholds are fixed constants (GIRI_Score_Utils::LEVEL_THRESHOLDS). They do not change per ingredient and are never subject to editorial adjustment.