L-Theanine
Product Forms
Dose Distribution
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Claims on Labels
Top-Rated L-Theanine Products
Evidence Summary
L-theanine is a non-protein amino acid found in tea that is widely studied for its effects on sleep, anxiety, and cognitive function. Research indicates it can improve sleep quality, reduce stress-related symptoms, and enhance cognitive performance, particularly when paired with caffeine.
Evidence by Condition
Systematic reviews and meta-analyses suggest L-theanine can improve sleep outcomes and quality.
Evidence indicates L-theanine can reduce stress-related symptoms and improve mood responses to cognitive stress.
L-theanine, especially when combined with caffeine, enhances cognitive performance, alertness, and selective attention.
There is limited evidence regarding the efficiency of L-theanine in alleviating symptoms of ADHD.
Effective Doses
Studies identified doses of approximately 97 mg to 100 mg, often in combination with caffeine.
Key Findings
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness (PMID 21040626)
- L-theanine administration can reduce stress-related symptoms and improve cognitive functions in healthy adults (PMID 31623400)
- Systematic reviews and meta-analyses support the efficacy of L-theanine for improving sleep outcomes (PMID 40056718, 41176609)
Limitations
Much of the research focuses on acute effects or specific combinations with caffeine, and there is a lack of robust evidence for long-term use in pediatric or neurodevelopmental populations.
Safety & Interactions
No specific interactions or contraindications were detailed in the provided research summaries.
AI-generated summary from 37 peer-reviewed studies. Not medical advice. Always consult a healthcare provider.
Claims vs. Evidence
| Claim Type | % of Products | Evidence Required | Status |
|---|---|---|---|
| All Other | 99% | Tier D (Unclassified) | ✅ Supported |
| Structure/Function | 92% | Tier C (DSHEA Structure/Function (no pre-approval)) | ✅ Supported |
| Nutrient | 22% | Tier D (Unknown) | ✅ Supported |
| Qualified Health | 0% | Tier B (FDA Qualified Health Claim) | ✅ Supported |
| No Claim | 0% | Tier D (No claim on label) | ✅ Supported |
Research by Topic
⚠️ FDA Safety Data
Research Evidence (37)
Objective: Sleep problems are a common complaint among adults worldwide, however, the use of prescription and over-the-counter products may not always be an appropriate or desirable solution. L-theanine is a naturally occurring, non-protein amino aci...
This systematic review ansd meta-analysis aimed to evaluate the effects of L-theanine, a non-proteinogenic amino acid found in tea, on sleep outcomes. Literature searches were conducted in five electronic databases (APA PsycINFO, CINAHL, Medline, Sco...
The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo tr...
This randomized, placebo-controlled, crossover, and double-blind trial aimed to examine the possible effects of four weeks L-theanine administration on stress-related symptoms and cognitive functions in healthy adults. Participants were 30 individual...
**Innocenti et al., 2023** | Int J Mol Sci | Systematic Review Innocenti Alice, Lentini Giuliana, ... Bruni Oliviero. The Role of Supplements and Over-the-Counter Products to Improve Sleep in Children: A Systematic Review. Int J Mol Sci. 2023-Apr-25;...
CONTEXT: The bioactive compounds found in tea from Camellia sinensis, namely theanine, caffeine, and polyphenols, can potentially improve short-term and long-term health outcomes. OBJECTIVE: The aim of this study was to assess the effects of tea, the...
This randomized, placebo-controlled, crossover and double-blind study investigates the effects of RLX2™ containing alpha-s1-casein tryptic hydrolysate and L-theanine in working adults affected by poor sleep quality. The supplement or placebo was rand...
BACKGROUND: L-theanine is a non-protein-forming amino acid found in tea. Limited evidence suggests that it improves selective attention. Sleep deprivation impairs attention and psychomotor reactions, affecting automobile driving. We aimed to determin...
The aim of this study was to compare 50 mg caffeine, with and without 100 mg L-theanine, on cognition and mood in healthy volunteers. The effects of these treatments on word recognition, rapid visual information processing, critical flicker fusion th...
A systematic review and meta-analysis was conducted on 11 randomized placebo-controlled human studies of acute effects of tea constituents L-theanine and epigallocatechin gallate, administered alone or in combination with caffeine, on cognitive funct...
BACKGROUND: Tourette syndrome (TS) is a neurodevelopmental disorder characterized by tics and co-occurring disorders. It has been suggested that anxiety occurs in 2-45% patients affected by Tourette syndrome. Despite dietary and nutritional factors h...
l-Theanine, the most abundant amino acid component in green tea, has anti-stress effects and refreshes the mental state. A recent study demonstrated that l-arginine, the second most abundant amino acid in green tea, might enhance the anti-stress effe...
**Al et al., 2025** | Nutrients | Systematic Review Al Shahab Shatha, Al Balushi Rawan, ... Jahrami Haitham. Efficiency of Different Supplements in Alleviating Symptoms of ADHD with or Without the Use of Stimulants: A Systematic Review. Nutrients. 20...
L-theanine (γ-glutamylethylamide) is an amino acid found primarily in the green tea plant. This study explored the effects of an L-theanine-based nutrient drink on mood responses to a cognitive stressor. Additional measures included an assessment of ...
**Mancini et al., 2017** | Phytomedicine | Systematic Review Mancini Edele, Beglinger Christoph, ... Borgwardt Stefan. Green tea effects on cognition, mood and human brain function: A systematic review. Phytomedicine. 2017-Oct-15;34:26-37. doi:10.101...
Objective: The research has shown an association with sensorimotor integration and symptomology of Autism Spectrum Conditions (ASC). Specific areas of the brain that are involved in sensorimotor integration, such as the cerebellum and basal ganglia, ...
The green tea amino acid, L-theanine (L-THE) is associated with several health benefits, including improvements in mood, cognition and a reduction of stress and anxiety-like symptoms. This systematic review evaluated the effect of pure L-THE intake, ...
L-theanine, an amino acid found in tea, and caffeine, found in tea and coffee, are claimed to enhance attention. We conducted a double-blind, placebo-controlled, counterbalanced, two-way crossover trial to determine the acute effects of a high-dose L...
**Moshfeghinia et al., 2024** | BMC Psychiatry | Systematic Review Moshfeghinia Reza, Sanaei Erfan, ... Ayano Getinet. The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review. BMC Psychiatry. 2...
**Anand et al., 2017** | Paediatr Drugs | Systematic Review Anand Shweta, Tong Henry, ... Wong Ian C K. Safety, Tolerability and Efficacy of Drugs for Treating Behavioural Insomnia in Children with Attention-Deficit/Hyperactivity Disorder: A Systemat...
**Shojaei-Zarghani et al., 2021** | Phytother Res | Systematic Review Shojaei-Zarghani Sara, Rafraf Maryam, Yari-Khosroushahi Ahmad. Theanine and cancer: A systematic review of the literature. Phytother Res. 2021-Sep;35(9):4782-4794. doi:10.1002/ptr....
Primary dysmenorrhea is one of the most common complaints among young women. This study aimed to evaluate the effects of chamomile and 1-theanine beverage intake on menstrual symptoms, pain intensity, mood, and sleep quality in young adult females wi...
l-theanine (γ-glutamylethylamide), an amino acid in green tea, has been shown to affect brain functions by relieving stress disorders, improving mood, and maintaining normal sleep. However, the cognitive functions for which theanine is effective are ...
The effect of a combination of magnesium, vitamins B6, B9, B12, rhodiola and green tea/L-theanine (Mg-Teadiola) on stress was evaluated in chronically stressed, otherwise healthy individuals. Effects on stress-related quality-of-life parameters (slee...
Sleep is a crucial component of health, and insomnia is among the most common and vexing of life-habit-related disorders. While dietary sleep-support supplements can improve sleep, choosing an effective dietary supplement can be challenging for users...
**Rocha et al., 2023** | Rev Paul Pediatr | Systematic Review Rocha Nathalia Sena, Correa Rogério do Espírito Santo Amorim, ... Bueno Cláudia Dizioli Franco. Association between sleep pattern and pharmacological treatment in children with attention d...
PURPOSE: Previous studies have investigated the effect of single or combined caffeine (CAF) and L-theanine (THE) intake on attention performance. However, its effect on shooting performance and cognitive performance in a sport is unknown. The aim of ...
**Barrett et al., 2013** | J Child Adolesc Psychopharmacol | Systematic Review Barrett Jessica R, Tracy Derek K, Giaroli Giovanni. To sleep or not to sleep: a systematic review of the literature of pharmacological treatments of insomnia in children a...
We examined the acute effects of L-theanine, caffeine and their combination on sustained attention, inhibitory control and overall cognition in boys with attention deficit hyperactivity disorder (ADHD). L-Theanine (2.5 mg/kg), caffeine (2.0 mg/kg), t...
Ingestion of L-theanine and L-tyrosine has been shown to reduce salivary stress biomarkers and improve aspects of cognitive performance in response to stress. However, there have been no studies to concurrently examine the impact of both L-theanine a...
INTRODUCTION: The purpose of this study was to investigate the efficacy and safety of L-theanine as an aid to the improvement of objectively measured sleep quality in a population of 98 male children formally diagnosed with attention-deficit/hyperact...
**NCT ID**: NCT06621797 **Phase**: NA **Status**: COMPLETED **Enrollment**: 15 **Completion**: 2024-09-26
Adaptogens are a group of substances capable to increase the nonspecific resistance of the organism to a wide range of harmful effects and stress. However, only limited data exist on their use in the composition of foods for special dietary uses. The...
In this randomised, placebo-controlled trial, adults with impaired sleep (Pittsburgh Sleep Quality Index ≥ 5) were randomly assigned using a minimization algorithm to receive a formulation containing L-theanine plus lemon balm, valerian, and saffron ...
BACKGROUND: Caffeine is a well-known ergogenic aid that can enhance physical and cognitive performance. However, it often induces side effects, such as anxiety and overstimulation, which can be problematic in high-pressure sports like wrestling. L-th...
Chronic stress-induced sleep disorders are characterized by disrupted sleep architecture and a significant reduction in slow-wave sleep (SWS). These disorders represent a major public health challenge and are mechanistically linked to the hyperactiva...
**Source**: FDA Center for Food Safety and Applied Nutrition (CFSAN) Adverse Event Reporting System **Total Events**: 5 **Serious Events**: 1 **Date Range**: 20170207 to 20241115 - **Fatigue**: 2
Details
L-Theanine
Overview
L-Theanine is a bioactive compound tracked in the biomedical knowledge base.
Also known as: theanine, gamma-glutamylethylamide, suntheanine
Role in Health
Detailed overview pending — this entity has sources compiled across multiple verticals.
Related Verticals
See sources-index for all verified sources referencing L-Theanine.
Safety Considerations
Safety data extraction pending.
Sources
See linked source pages for full provenance.
Related Supplements
Frequently Asked Questions
What is L-theanine and what are its main benefits?
L-theanine is a non-protein amino acid naturally found in tea. There is strong evidence that it can improve sleep quality and moderate evidence that it helps reduce stress and enhance focus.
Does L-theanine help with sleep?
Yes, there is strong evidence from systematic reviews and meta-analyses suggesting that L-theanine can improve sleep outcomes and overall sleep quality.
Can L-theanine reduce anxiety and stress?
There is moderate evidence that L-theanine can reduce stress-related symptoms. It has also been shown to improve mood responses to cognitive stress.
Will L-theanine help me focus or stay alert?
There is moderate evidence that L-theanine enhances cognitive performance, alertness, and selective attention. This effect is particularly effective when L-theanine is paired with caffeine.
What is the effective dose of L-theanine?
Research has identified effective doses of approximately 97 mg to 100 mg. These doses are often studied in combination with caffeine to improve cognitive performance.
Is L-theanine safe and are there any drug interactions?
No specific side effects, contraindications, or groups that should avoid L-theanine were identified in the research. Additionally, there are no documented drug interactions for this supplement.
Does L-theanine help with ADHD symptoms?
There is currently insufficient evidence to determine if L-theanine is effective in alleviating symptoms of ADHD.
Answers generated from research evidence. Not medical advice.