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L-Theanine 100 mg

Metabolic Maintenance
4.8
★ ★ ★ ★ ★
(86 ratings)
Theanine 100 mg
Glycine 300 mg
Product Image
Score80
Suntheanine provides dependable calm-focus support, while low glycine and premium cost limit sleep depth and value.
How scoring works
Quantity:60 Capsule(s) • (60 servings)
Goals:
Productivity Boost
Brain Health
Cognitive Support
Stress Relief
Sleep Support
Mental Focus
Mood Support

Score 80

Suntheanine provides dependable calm-focus support, while low glycine and premium cost limit sleep depth and value.
How scoring works
$32.50($0.54 per serving)
iHerb
$ 32.50
Pure Formulas
$ 35.00
Report prices

Analysis

One hundred milligrams of Suntheanine offers a well-characterized L-theanine source for calm concentration and stress-related tension. The ingredient can support a relaxed cognitive state without acting as a direct stimulant.

Three hundred milligrams of glycine is compatible with the calming purpose but too low for a typical standalone sleep serving. Both active amounts are transparent, and the compact formula avoids unnecessary ingredients.

The capsule suits daytime calm or pairing with a modest caffeine source. It provides limited memory, energy, circadian, or broad stress-adaptation coverage, and its cost is premium for the two actives.

Who is it for
  • Adults seeking calm without a stimulant
  • Users prioritizing branded theanine
Best for
  • Stress-related concentration
  • Relaxed daytime focus

Pros

  • Branded Suntheanine
  • Useful theanine amount
  • Simple two-ingredient design

Cons

  • Glycine is underdosed for sleep
  • No alertness ingredient
  • Premium serving cost

Warnings

  • L-theanine may lower blood pressure; monitor for dizziness with blood-pressure medicine.
  • The calming effect may add to alcohol or sedating medicines in sensitive users.
  • Try the first dose when driving or other demanding tasks are not required.

Nutrient quality

94 Highest impact

Branded L-theanine and a focused two-active design provide strong quality confidence. The modest glycine amount is the main dose limitation.

Ingredient transparency

83 Highest impact

Every listed active has a specific amount, and no proprietary blend hides key doses. The serving count is clear, but intake directions and non-active ingredients are not supplied.

Customer satisfaction

66 High impact

Customer sentiment is exceptionally strong, and the review volume still limits certainty. No review excerpts are supplied, so repeated complaints and purpose fit cannot be verified.

Value for money

70 High impact

A well-characterized branded active provides genuine premium quality. High serving cost and modest glycine depth limit competitive value.

Report analysis

Goals

Productivity Boost
Productivity Boost
Impact
Highest effect
B+ Goal FitA Strength of SupportC CoverageA Formula Quality
Theanine · 100 mg

Branded L-theanine is provided at a useful amount for calm attention and may help reduce distraction from tension. Glycine adds a calming companion, but neither ingredient creates strong alertness on its own.

The compact formula is transparent and uses a well-characterized theanine source. It is best suited to relaxed concentration or pairing with a modest caffeine source rather than driving energy by itself.

Study evidence
Theanine Supportive 5 studies
Brain Health
Brain Health
Impact
Highest effect
B Goal FitA Strength of SupportC- CoverageA Formula Quality

Suntheanine supplies a well-characterized L-theanine source at a useful amount for calm, focused attention. Glycine adds a simple complementary calming pathway without obscuring the main active.

The formula is narrow and does not address memory, neuronal structure, or brain energy. Strong sourcing, full disclosure, and a clean two-ingredient design nevertheless make it a dependable focused option.

Study evidence
Theanine Supportive 17 studies
Cognitive Support
Cognitive Support
Impact
Highest effect
B Goal FitA- Strength of SupportC CoverageA Formula Quality
Theanine · 100 mg

Branded L-theanine at 100 mg provides focused support for calm attention without a stimulant. Glycine complements relaxation, although its amount is modest compared with typical sleep-focused use.

The formula is transparent and well constructed for one narrow cognitive state. It does not address memory, cerebral circulation, or mental energy.

Study evidence
Theanine Supportive 25 studies
Stress Relief
Stress Relief
Impact
Highest effect
B+ Goal FitB+ Strength of SupportC CoverageA Formula Quality
Glycine · 300 mgTheanine · 100 mg

Suntheanine provides a well-characterized form of L-theanine at a useful amount for calm without marked sedation. Glycine adds a compatible relaxation signal, though its amount is too modest for strong sleep support.

The focused two-ingredient design is transparent and easy to assess. Evidence and formulation quality are strongest for theanine, making the product better suited to acute calm than broad stress adaptation.

Study evidence
Glycine Supportive 1 study
Theanine Supportive 16 studies
Sleep Support
Sleep Support
Impact
High effect
B+ Goal FitB Strength of SupportC CoverageA+ Formula Quality
Theanine · 100 mgGlycine · 300 mg

Branded theanine directly supports relaxation, and glycine adds a complementary calming amino acid. The two-ingredient formula is transparent and simple.

Theanine uses a practical lower amount, while glycine is far below the amount commonly used in sleep studies. The formula may support winding down but lacks circadian or mineral coverage.

Study evidence
Glycine Supportive 3 studies
Theanine Supportive 8 studies
Mental Focus
Mental Focus
Impact
High effect
C+ Goal FitA- Strength of SupportD CoverageA- Formula Quality
Theanine · 100 mg

Branded Suntheanine provides a well-characterized L-theanine form that may support calm concentration during stress. The disclosed amount is practical and the small glycine addition keeps the formula simple.

L-theanine alone is less likely to improve alertness than a balanced pairing with caffeine. Glycine is too modest to add meaningful cognitive breadth, so the formula remains narrowly focused.

Study evidence
Theanine Supportive 19 studies
Mood Support
Mood Support
Impact
High effect
C Goal FitB+ Strength of SupportD+ CoverageA Formula Quality

Suntheanine may support a calmer emotional state and reduce tension without marked sedation. Glycine is compatible but too modest to provide meaningful mood depth.

The branded theanine source and exact dosing offer strong quality confidence. The formula is useful for stress-related irritability or tension but does not address broader mood pathways such as serotonin production or adaptation.

Study evidence
Glycine Mixed 3 studies
Theanine Supportive 12 studies

Ingredients

IngredientAmount per serving
L-Theanine Suntheanine
100 mg
Glycine
300 mg
Gluten Free Adults 18–50 Dairy Free
Report overview
Theanine · 100 mg OverallScore90
A+ Active Ingredient Quality & BioavailabilityA+ Dose, Safety & Label TransparencyD+ Value

Explicit L-theanine identity and Suntheanine branding provide strong isomer and purity confidence. The clearly disclosed amount falls within the optimal range for calm and focused support. Suntheanine adds a strong purity signal, while dose-adjusted cost remains premium.

View ingredientView products
Glycine · 300 mg OverallScore64
C Active Ingredient Quality & BioavailabilityC+ Dose, Safety & Label TransparencyB- Value

The glycine amount is clear, but no premium grade, branded source, or purity certification is provided. Its 300 mg contribution is modest alone but works as part of the theanine relaxation formula. Other well-chosen actives improve formula-level value despite weak glycine-only economics.

View ingredientView products
Loading alternative details
84 Performance

Suntheanine L-Theanine 125 mg

Natural Factors Stress-Relax
<p>Branded Suntheanine at a somewhat larger amount strengthens relaxation and calm-focus coverage while preserving ingredient assurance. The single-active design is easy to assess and avoids the original token glycine addition.</p>
85 Performance

L-Theanine 150 mg

Solgar
<p>A larger Suntheanine serving offers stronger calm-focus support with the same well-characterized source quality. The streamlined formula avoids unrelated actives and maintains clear purpose.</p>
87 Performance

L-Theanine 200 mg Double Strength

Swanson
<p>A substantial branded Suntheanine amount improves potency for relaxation and focused calm. The focused capsule retains strong ingredient assurance without relying on a token glycine dose.</p>
85 Budget

Double Strength L-Theanine 200 mg

NOW
<p>A larger clearly disclosed L-theanine amount offers strong calm-focus support at a much lower serving cost. Generic sourcing has less purity assurance than Suntheanine, and the small inositol amount adds little.</p>
85 Budget

L-Theanine 200 mg

California Gold Nutrition
<p>A larger L-theanine amount supports relaxation and stress-related focus at a lower recurring cost. No branded source or purity marker is supplied, so ingredient assurance is weaker than the original Suntheanine.</p>
82 Budget

Theanine 100 mg

Jarrow Formulas
<p>The same practical L-theanine amount provides moderate daily support at a lower serving cost. Source and purity markers are missing, making raw-material assurance weaker than the original branded active.</p>
87 Value

L-Theanine 100 mg

California Gold Nutrition
<p>AlphaWave L-theanine matches the original practical amount while providing another characterized source at much stronger serving value. The focused formula leaves out glycine, which was too modest in the original to add much effect.</p>
85 Value

Glycine Powder

Metabolic Maintenance
<p>A single-ingredient powder can scale to meaningful multi-gram glycine use at favorable recurring value. No premium purity grade is stated, and it does not provide the original L-theanine support.</p>
82 Value

Advanced Magnesium Complex

AOR Advanced Orthomolecular Research Advanced
<p>Absorbable magnesium forms with a substantial glycine yield provide broader stress-related mineral support at favorable value. Elemental magnesium is not separated by form, and sensitive users may experience loose stools.</p>
Report alternatives

Sources

Published studies used for the product analysis and the top-ranked studies for each ingredient and goal.

  1. The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review.
    Soh J; Raventhiran S; Lee JH; Lim ZX; Goh J; Kennedy BK; Maier AB · GeroScience · 2024
    Systematic reviewSleep Support forGlycine
  2. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers.
    Bannai M; Kawai N; Ono K; Nakahara K; Murakami N · Frontiers in neurology · 2012
    Clinical trial7 participantsSleep Support forGlycine
  3. The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.
    Williams JL; Everett JM; D'Cunha NM; Sergi D; Georgousopoulou EN; Keegan RJ; McKune AJ; Mellor DD; Anstice N; Naumovski N · Plant foods for human nutrition (Dordrecht, Netherlands) · 2020
    Systematic review9 studies pooledStress Relief Mood Support forTheanine
  4. L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.
    Sarris J; Byrne GJ; Cribb L; Oliver G; Murphy J; Macdonald P; Nazareth S; Karamacoska D; Galea S; Short A; Ee C; Birling Y; Menon R; Ng CH · Journal of psychiatric research · 2020
    Randomized trial46 participantsStress Relief Sleep Support forTheanine
  5. Promising, but Not Completely Conclusive-The Effect of l-Theanine on Cognitive Performance Based on the Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Clinical Trials.
    Mátyus RO; Szikora Z; Bodó D; Vargáné Szabó B; Csupor É; Csupor D; Tóth B · Journal of clinical medicine · 2025
    Meta-analysis148 participants5 studies pooledMental Focus Cognitive Support forTheanine
  6. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial.
    Hidese S; Ogawa S; Ota M; Ishida I; Yasukawa Z; Ozeki M; Kunugi H · Nutrients · 2020
    Randomized trial30 participantsBrain Health Cognitive Support Sleep Support forTheanine
  7. A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave® L-Theanine on Stress in a Healthy Adult Population.
    Evans M; McDonald AC; Xiong L; Crowley DC; Guthrie N · Neurology and therapy · 2021
    Randomized trialBrain Health Stress Relief forTheanine
  8. 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.
    Payne ER; Aceves-Martins M; Dubost J; Greyling A; de Roos B · Nutrition reviews · 2025
    Meta-analysis50 studies pooledBrain Health Cognitive Support Mental Focus forTheanine
  9. Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task.
    Foxe JJ; Morie KP; Laud PJ; Rowson MJ; de Bruin EA; Kelly SP · Neuropharmacology · 2012
    Randomized trial27 participantsBrain Health Cognitive Support forTheanine
  10. Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study.
    Baba Y; Inagaki S; Nakagawa S; Kaneko T; Kobayashi M; Takihara T · Journal of medicinal food · 2021
    Randomized trialBrain Health Mental Focus Productivity Boost forTheanine
  11. Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study.
    Dassanayake TL; Wijesundara D; Kahathuduwa CN; Weerasinghe VS · Nutritional neuroscience · 2023
    Randomized trial32 participantsCognitive Support forTheanine
  12. Acute effects of theanine, caffeine and theanine-caffeine combination on attention.
    Kahathuduwa CN; Dassanayake TL; Amarakoon AMT; Weerasinghe VS · Nutritional neuroscience · 2018
    Clinical trial20 participantsCognitive Support Mental Focus forTheanine
  13. Safety and Efficacy of AlphaWave® L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled Trial.
    Moulin M; Crowley DC; Xiong L; Guthrie N; Lewis ED · Neurology and therapy · 2024
    Randomized trial30 participantsMental Focus Productivity Boost Stress Relief forTheanine
  14. Effect of L-theanine on selective attention in a traffic-related reaction task in sleep-deprived young adults: a double-blind placebo-controlled, crossover study.
    Karunaratne UW; Dassanayake TL · Nutritional neuroscience · 2025
    Randomized trial24 participantsMental Focus forTheanine
  15. [Augmentation of antipsychotics with glycine may ameliorate depressive and extrapyramidal symptoms in schizophrenic patients--a preliminary 10-week open-label study].
    Strzelecki D; Kropiwnicki P; Rabe-Jabłońska J · Psychiatria polska · 2014
    Single-arm trial29 participantsMood Support forGlycine
  16. Markers of glutamate signaling in cerebrospinal fluid and serum from patients with bipolar disorder and healthy controls.
    Pålsson E; Jakobsson J; Södersten K; Fujita Y; Sellgren C; Ekman CJ; Ågren H; Hashimoto K; Landén M · European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology · 2015
    Cross-sectional study327 participantsMood Support forGlycine
  17. Erythrocyte glycine in depressed, hypomanic, and euthymic bipolar patients treated with lithium carbonate.
    Peselow ED; Deutsch SI; Stanley M; Banay-Schwartz M; Virgilio J; Fieve RR · Psychopharmacology · 1983
    Cross-sectional study27 participantsMood Support forGlycine
  18. l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial.
    Shamabadi A; Kafi F; Arab Bafrani M; Asadigandomani H; A Basti F; Akhondzadeh S · Journal of affective disorders · 2023
    Randomized trial60 participantsMood Support forTheanine
  19. L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study.
    Ritsner MS; Miodownik C; Ratner Y; Shleifer T; Mar M; Pintov L; Lerner V · The Journal of clinical psychiatry · 2011
    Randomized trial60 participantsMood Support Stress Relief forTheanine
  20. 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.
    Deshpande SS; Kurdi M; Baiju A; Athira AS; Sarasamma AG; Gangadharan AK · Journal of anaesthesiology, clinical pharmacology · 2025
    Randomized trial168 participantsMood Support Stress Relief forTheanine
  21. Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stress.
    Unno K; Tanida N; Ishii N; Yamamoto H; Iguchi K; Hoshino M; Takeda A; Ozawa H; Ohkubo T; Juneja LR; Yamada H · Pharmacology, biochemistry, and behavior · 2014
    Randomized trial20 participantsMood Support forTheanine
  22. Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials.
    Gerolymos C; Saddier E; Boyer L; Fond G · Molecular psychiatry · 2026
    Meta-analysis1,168 participants31 studies pooledProductivity Boost forTheanine
  23. Effects of L-theanine on cognition, mood and sleep: evidence from human trials.
    Cotter J; Kilpatrick HE · Frontiers in nutrition · 2026
    Narrative reviewProductivity Boost forTheanine
  24. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together.
    Rogers PJ; Smith JE; Heatherley SV; Pleydell-Pearce CW · Psychopharmacology · 2008
    Randomized trial48 participantsProductivity Boost forTheanine
  25. New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep.
    Bannai M; Kawai N · Journal of pharmacological sciences · 2012
    Narrative reviewSleep Support forGlycine
  26. 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.
    Kurdi MS; As A; Ladhad DA; Mitragotri MV; Baiju A · Indian journal of palliative care · 2024
    Randomized trial120 participantsSleep Support forTheanine
  27. The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis.
    Bulman A; D'Cunha NM; Marx W; Turner M; McKune A; Naumovski N · Sleep medicine reviews · 2025
    Meta-analysis897 participants19 studies pooledSleep Support forTheanine
  28. In Search of a Safe Natural Sleep Aid.
    Rao TP; Ozeki M; Juneja LR · Journal of the American College of Nutrition · 2016
    Narrative reviewSleep Support forTheanine
  29. Oral supplementation with glycine reduces oxidative stress in patients with metabolic syndrome, improving their systolic blood pressure.
    Díaz-Flores M; Cruz M; Duran-Reyes G; Munguia-Miranda C; Loza-Rodríguez H; Pulido-Casas E; Torres-Ramírez N; Gaja-Rodriguez O; Kumate J; Baiza-Gutman LA; Hernández-Saavedra D · Canadian journal of physiology and pharmacology · 2014
    Randomized trial60 participantsStress Relief forGlycine
  30. Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial.
    White DJ; de Klerk S; Woods W; Gondalia S; Noonan C; Scholey AB · Nutrients · 2016
    Randomized trial34 participantsStress Relief forTheanine