L-Theanine
Amino Acid ·Exploratory record · not publication-reviewed ·Updated July 13, 2026
Unique amino acid found primarily in green tea. Promotes calm alertness without drowsiness. Synergizes exceptionally well with caffeine for focused energy.
Exploratory record, not a reviewed medical publication.
See the editorial and medical-review policies for the publication gate.
This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.
What the research says.
A quick, data-only summary. The full evidence, dosing, and sources are below.
L-Theanine is an amino acid most often used for calm focus, stress-response support, sleep-quality research. NutriStack rates the overall evidence as moderate. A typical adult dose is 100–400 mg daily, commonly taken as l-theanine (suntheanine is a patented pure form). This profile indexes 22 sources.
The bottom line
Evidence rating moderate. Most-documented uses: calm focus, stress-response support, sleep-quality research. 22 sources indexed (2006–2025), with 0 interaction records on file.
How it works, mechanistically.
Core mechanism
Crosses the blood-brain barrier and increases alpha brain wave activity (associated with relaxed focus). Modulates GABA, serotonin, and dopamine levels. Weakly binds AMPA/kainate glutamate receptors (80- to 30,000-fold less affinity than glutamate). Enhances BDNF production.18,5
Dosing & protocol.
Stack with caffeine (2:1 theanine:caffeine) for ideal focused energy; can take any time3,5
What it actually costs.
Real-world pricing across three quality tiers. Assumes L-Theanine.
Assumes about 200 mg/day. Branded forms and combo sleep products are what usually push this into premium pricing. Updated 2026-04-02.
The same dose, as food.
How much you'd eat to match a supplemental dose.
Tea theanine varies by tea type, growing conditions, and brewing strength.
Full safety detail.
Side effects
- Very well tolerated
- Mild headache (rare)
- Drowsiness at high doses
Contraindications
- Blood pressure medications (may lower BP further)
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
3- 1Effects 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.PMIDPayne ER, Aceves-Martins M, Dubost J et al. · Nutrition Reviews · 2025
L-theanine improved attention and reaction time, particularly when combined with caffeine. L-theanine alone showed benefits for sleep quality.
- 2Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis.PMIDZhang W, Yan Y, Wu Y et al. · Pharmacological Research · 2022
L-theanine was among the medicinal herbs showing significant anxiolytic effects in a network meta-analysis of randomized controlled trials.
- 3Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysisPMIDCamfield DA et al. · Nutr Rev · 2014
Moderate effect sizes for combined caffeine and L-theanine on alertness, attentional switching accuracy in first 2 hours post-dose
Randomized controlled trials
11- 4Comparison of the effects of two amino acids, Gamma-aminobutyric acid (GABA) and L-theanine, on sedation, anxiety, and cognition in preoperative surgical patients - A randomized controlled studyPMIDDeshpande SS, Kurdi M, Baiju A et al. · Journal of anaesthesiology, clinical pharmacology · 2025
Deshpande SS, Kurdi M, Baiju A et al.. Comparison of the effects of two amino acids, Gamma-aminobutyric acid (GABA) and L-theanine, on sedation, anxiety, and cognition in preoperative surgical patients - A randomized controlled study. Journal of anaesthesiology, clinical pharmacology. 2025
- 5Safety and Efficacy of AlphaWave(®) L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled TrialPMIDMoulin M, Crowley DC, Xiong L et al. · Neurology and therapy · 2024
Moulin M, Crowley DC, Xiong L et al.. Safety and Efficacy of AlphaWave(®) L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled Trial. Neurology and therapy. 2024
- 6Comparison Between Efficacy of Oral Melatonin and Oral L-theanine in Improving Sleep in Cancer Patients Suffering From Insomnia: A Randomised Double-blinded Placebo-controlled StudyPMIDKurdi MS, As A, Ladhad DA et al. · Indian journal of palliative care · 2024
Kurdi MS, As A, Ladhad DA et al.. Comparison Between Efficacy of Oral Melatonin and Oral L-theanine in Improving Sleep in Cancer Patients Suffering From Insomnia: A Randomised Double-blinded Placebo-controlled Study. Indian journal of palliative care. 2024
- 7Dietary supplementation with Lactium and L-theanine alleviates sleep disturbance in adults: a double-blind, randomized, placebo-controlled clinical studyPMIDLim SE, Kim HS, Lee S et al. · Frontiers in nutrition · 2024
Lim SE, Kim HS, Lee S et al.. Dietary supplementation with Lactium and L-theanine alleviates sleep disturbance in adults: a double-blind, randomized, placebo-controlled clinical study. Frontiers in nutrition. 2024
- 8l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trialPMIDShamabadi A, Kafi F, Arab Bafrani M et al. · Journal of affective disorders · 2023
Shamabadi A, Kafi F, Arab Bafrani M et al.. l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial. Journal of affective disorders. 2023
- 9GABA and l-theanine mixture decreases sleep latency and improves NREM sleepPMIDKim S et al. · Pharm Biol · 2019
GABA/L-theanine mixture has positive synergistic effect on sleep quality and duration vs either component alone
- 10L-Theanine as a functional food additive: effects on cognition, stress, and sleep qualityHidese S, Ogawa S, Ota M et al. · Nutrients · 2019
- 11Anti-stress effect of L-theanine on students during pharmacy practice: a randomized controlled trialUnno K, Tanida N, Ishii N et al. · Pharmacol Biochem Behav · 2013
- 12The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertnessPMIDOwen GN et al. · Nutr Neurosci · 2010
97 mg L-theanine + 40 mg caffeine significantly improved task-switching accuracy and self-reported alertness while reducing tiredness
- 13Effects of L-theanine on attention and reaction time response in healthy adultsNobre AC, Rao A, Owen GN · Asia Pac J Clin Nutr · 2008
- 14The acute effects of L-theanine on stress and anxiety: a double-blind, placebo-controlled crossover trialKimura K, Ozeki M, Juneja LR et al. · Biol Psychol · 2007
Reviews & position papers
5- 15Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trialsPMIDWilliams JL et al. · J Am Nutr Assoc · 2025
200-450 mg/day of L-theanine is safe and effective for supporting healthy sleep through anxiolysis rather than sedation
- 16The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic ReviewPMIDEverett JM et al. · Plant Foods Hum Nutr · 2020
Review suggests 200-400 mg/day L-theanine may support stress-related symptoms in people exposed to stressful conditions; this should not be framed as anxiety treatment.
- 17Synergistic effects of L-theanine and caffeine on cognitive performance: a systematic reviewCamfield DA, Stough C, Farber J et al. · Nutr Rev · 2014
- 18L-theanine, a natural constituent in tea, and its effect on mental statePMIDNobre AC et al. · Asia Pac J Clin Nutr · 2008
L-theanine increases alpha brain wave activity associated with relaxed alertness without drowsiness
- 19The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agentPMIDNathan PJ et al. · J Herb Pharmacother · 2006
L-theanine increases brain serotonin, dopamine, GABA levels and has micromolar affinities for AMPA, Kainate and NMDA receptors
Mechanistic & preclinical
1- 20L-Theanine prevents long-term affective and cognitive side effects of adolescent delta-9-tetrahydrocannabinol exposureMurphy M, Mills S, Winstone J et al. · Front Behav Neurosci · 2017
Reference material
2- 21Bulman A, D'Cunha NM, Marx W et al.. The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis. Sleep medicine reviews. 2025Source linkedPMID
- 22Moshfeghinia R, Sanaei E, Mostafavi S et al.. The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review. BMC psychiatry. 2024Source linkedPMID
Common questions.
Quick answers about L-Theanine, drawn from the data on this page.
What is L-Theanine?
Unique amino acid found primarily in green tea. Promotes calm alertness without drowsiness. Synergizes exceptionally well with caffeine for focused energy.
What is L-Theanine used for?
Commonly cited benefits of L-Theanine include: Calm focus; Stress-response support; Sleep-quality research; Caffeine synergy. NutriStack rates the overall evidence as moderate.
What is a typical dose of L-Theanine?
A typical adult dose of L-Theanine is 100–400 mg daily. The commonly recommended form is L-theanine (Suntheanine is a patented pure form). These are general ranges, not personalized advice; confirm the right dose with a clinician.
What are the side effects of L-Theanine?
Reported side effects include very well tolerated, mild headache (rare), drowsiness at high doses. This is educational information; check with a healthcare professional before use.
How strong is the evidence for L-Theanine?
NutriStack rates this as Moderate, meaning several aligned RCTs or one large RCT plus supporting reviews. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
Deep dives & adjacent profiles.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
Use this with your stack
L-Theanine in NutriStack.
Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.