Theanine
15 benefits mapped to clinical evidence across supplements.
Dose per serving from products
4,937 products in our catalogue print how much Theanine a serving holds.
Most common: 100 mg to 250 mg, 38% of 4,937 products.
| Dose per serving | Products |
|---|---|
| 10 mg or less | 149 |
| 10 mg to 25 mg | 226 |
| 25 mg to 50 mg | 780 |
| 50 mg to 100 mg | 1,482 |
| 100 mg to 250 mg | 1,856 |
| 250 mg to 500 mg | 389 |
| over 500 mg | 55 |
Dose per serving from research
40 study groups in 31 studies say how much Theanine participants took a day.
These are the doses the studies gave. They are not a recommendation.
Most common: 100 mg to 250 mg, 40% of 40 study groups.
| Daily dose | Study groups |
|---|---|
| 25 mg or less | 1 |
| 25 mg to 50 mg | 3 |
| 50 mg to 100 mg | 6 |
| 100 mg to 250 mg | 16 |
| 250 mg to 500 mg | 11 |
| 500 mg to 1 g | 3 |
Commonly used together
17 of 33 study groups took Theanine with something else. Shown: what 3 or more different studies gave.
What was given together, not what works together.
| Taken with | Study groups |
|---|---|
| Caffeine | 5 |
| Cystine | 3 |
Benefit Evidence
Anxiety, sAA ↓
BP stress response ↓
Cortisol, anxiety ↓
Anxiety↓; sAA↓
Stress markers↓; BP↓
Anxiety↓; HR↓
Mood: +
Anxiety/stress: −
Lower anxiety/stress
Mood lift +56%
Less stress markers
↓ physiological stress
↓ anxiety/stress -17 to 22
↓ cortisol/HRV response
Lower anxiety/stress markers
Reduced stress response
Sleep quality + duration
Deep sleep +50%
Sleep onset −24 min
Sleep quality improved
Attention speed+accuracy
Fatigue/stress down
Attention + fast RT
Working memory + accuracy
Alertness, -tiredness
Attention/working memory up
+1.8 memory points
Caffeine combo boosts memory
Attention/working memory ↑
Memory recall modest ↑
Faster attention RTs
Better ERP attention
+38 ms
faster, sharper attention
−30 to −150 ms
Alertness/attention +accuracy
Fatigue/stress - sAA, +sleep
Alertness, less fatigue
Reaction time, +15–20 ms
Anxiety, sAA ↓
BP stress response ↓
Cortisol, anxiety ↓
Anxiety↓; sAA↓
Stress markers↓; BP↓
Anxiety↓; HR↓
Mood: +
Anxiety/stress: −
Lower anxiety/stress
Mood lift +56%
Less stress markers
↓ physiological stress
↓ anxiety/stress -17 to 22
↓ cortisol/HRV response
Lower anxiety/stress markers
Reduced stress response
Sleep quality + duration
Deep sleep +50%
Sleep onset −24 min
Sleep quality improved
Attention speed+accuracy
Fatigue/stress down
Attention + fast RT
Working memory + accuracy
Alertness, -tiredness
Attention/working memory up
+1.8 memory points
Caffeine combo boosts memory
Attention/working memory ↑
Memory recall modest ↑
Faster attention RTs
Better ERP attention
+38 ms
faster, sharper attention
−30 to −150 ms
Alertness/attention +accuracy
Fatigue/stress - sAA, +sleep
Alertness, less fatigue
Reaction time, +15–20 ms
Research sources
Stress & Anxiety (13)
- Effect of Combined Ingestion of L-Theanine and L-Arginine for Short-Term Psychological Stress in Young Adults: A Randomized Placebo-Controlled Study
PubMed ID: 36596553
Acute randomized study: single-dose theanine (±arginine) significantly reduced sAA vs placebo after a stressor (robust physiologic evidence).
- l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 37084960
Adjunctive improvement in depressive symptoms may reduce worry and rumination.
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Dose–response study showed improved sustained-attention and visuomotor RTs with L-theanine; supports reduced task-related stress/strain (behavioral evidence).
- Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study
PubMed ID: 35565828
Large multi-ingredient RCT including theanine produced clinically relevant reductions in self-reported stress (attribution partial).
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
Decreases in trait anxiety and depressive symptoms indicate reduced everyday worry over 4 weeks.
- 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
PubMed ID: 21208586
8-week augmentation reduced anxiety scores in patients with schizophrenia/schizoaffective disorder.
- Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
PubMed ID: 26797633
200 mg reduced subjective stress at 1 h and lowered salivary cortisol at 3 h (double-blind crossover).
- Serum levels of brain-derived neurotrophic factor and cortisol to sulfate of dehydroepiandrosterone molar ratio associated with clinical response to L-theanine as augmentation of antipsychotic therapy in schizophrenia and schizoaffective disorder patients
PubMed ID: 21617527
L-theanine augmentation correlated clinical symptom improvements (dysphoria/anxiety) with biomarker changes (BDNF, cortisol:DHEAS).
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
L-theanine+caffeine reduced anxiety and improved attention versus placebo in sleep-deprived adults, consistent with reduced jitteriness.
- Effect of matcha green tea on cognitive functions and sleep quality in older adults with cognitive decline: A randomized controlled study over 12 months
PubMed ID: 39213264
12-month matcha (contains theanine) significantly improved social acuity/emotion-recognition performance in older adults with early cognitive decline.
- Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together
PubMed ID: 17891480
Theanine antagonised caffeine's blood‑pressure increase in 48 adults, indicating mitigation of a physiological 'jitter' marker.
- Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials
PubMed ID: 30308973
Matcha reduced STAI anxiety and sAA vs placebo (human RCT with biochemical marker).
- L-theanine combination therapy with fluvoxamine in moderate-to-severe obsessive-compulsive disorder: A placebo-controlled, double-blind, randomized trial
PubMed ID: 37169515
Significant reduction in obsession severity (OCD) suggests benefit for pathological worry/rumination.
Mood balance (13)
- L-theanine combination therapy with fluvoxamine in moderate-to-severe obsessive-compulsive disorder: A placebo-controlled, double-blind, randomized trial
PubMed ID: 37169515
Adjunctive benefit for OCD obsession severity and reduced total Y-BOCS suggests broader mental-health benefit.
- Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials
PubMed ID: 30308973
Matcha (high-theanine) reduced STAI anxiety and salivary stress enzyme in randomized study (moderate N, food matrix).
- 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
PubMed ID: 21208586
400 mg/day adjunct reduced anxiety and some psychopathology in patients on antipsychotics.
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
4-week 200 mg/day L-theanine RCT reduced anxiety and depression scores vs placebo (direct mood effect).
- Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study
PubMed ID: 35565828
Multi-ingredient product including theanine reduced perceived stress (large RCT) — attribution partial.
- Use of Nutritional Supplements Based on L-Theanine and Vitamin B6 in Children with Tourette Syndrome, with Anxiety Disorders: A Pilot Study
PubMed ID: 35215501
Open-label L-theanine + B6 trial in children showed large tic/anxiety drops (unblinded, combined supplement).
- l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 37084960
Adjunctive 200 mg/day L-theanine with sertraline produced clinically meaningful reductions in depressive symptoms vs placebo.
- L-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients: a randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 37697164
Adjunctive improvements in negative and general psychopathology in schizophrenia support improved mental-health status.
- [Clinical evaluation of the efficacy of innovative spread of a given fatty acid composition enriched by adaptogens]
PubMed ID: 37801460
Enriched spread increased general well‑being (SAN) scores in a randomized trial (combination product including theanine).
- Effect of Combined Ingestion of L-Theanine and L-Arginine for Short-Term Psychological Stress in Young Adults: A Randomized Placebo-Controlled Study
PubMed ID: 36596553
Acute theanine reduced sAA stress response after mental task (physiologic correlate of reduced stress/anxiety).
- Effects of chamomile and -theanine beverage on menstrual pain, menstrual symptoms, mood, and sleep quality in young women experiencing primary dysmenorrhea: A randomized, double-blind, placebo-controlled study
PubMed ID: 41525193
Chamomile + L-theanine beverage produced marked reductions in menstrual pain and clear mood improvements (large RCT effect, but combo product).
- Serum levels of brain-derived neurotrophic factor and cortisol to sulfate of dehydroepiandrosterone molar ratio associated with clinical response to L-theanine as augmentation of antipsychotic therapy in schizophrenia and schizoaffective disorder patients
PubMed ID: 21617527
Clinical symptom improvements associated with neurotrophic and steroidal biomarkers point to broad well-being effects.
- Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
PubMed ID: 26797633
Single 200 mg drink substantially reduced subjective stress versus placebo at 1 h.
Stress resilience (10)
- Serum levels of brain-derived neurotrophic factor and cortisol to sulfate of dehydroepiandrosterone molar ratio associated with clinical response to L-theanine as augmentation of antipsychotic therapy in schizophrenia and schizoaffective disorder patients
PubMed ID: 21617527
L-theanine adjunctive therapy showed clinical symptom improvements associated with BDNF and cortisol:DHEAS changes—biological evidence of balanced stress response.
- L-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients: a randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 37697164
Adjunctive L-theanine modestly improved negative and overall psychopathology in schizophrenia, pointing to some enhancement in emotional/clinical resilience.
- L-theanine combination therapy with fluvoxamine in moderate-to-severe obsessive-compulsive disorder: A placebo-controlled, double-blind, randomized trial
PubMed ID: 37169515
L-theanine added to fluvoxamine reduced obsession severity in OCD — suggests improved clinical symptom resilience in this population.
- l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 37084960
Adjunctive L-theanine enhanced response/remission to sertraline, indicating improved capacity to recover from depressive episodes (emotional resilience).
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
4-week L-theanine reduced trait anxiety and depression scores, indicating improved emotional resilience.
- 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
PubMed ID: 21208586
8-week augmentation reduced anxiety/psychopathology suggesting improved resilience in clinical patients.
- Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
PubMed ID: 26797633
Acute reductions in cortisol and subjective stress demonstrate an ability to modulate stress axis responsivity.
- Matcha consumption maintains attentional function following a mild acute psychological stress without affecting a feeling of fatigue: A randomized placebo-controlled study in young adults
PubMed ID: 33744591
Matcha preserved attention after mild stress and improved emotion perception — behavioral evidence for resilience to stress.
- Effect of Combined Ingestion of L-Theanine and L-Arginine for Short-Term Psychological Stress in Young Adults: A Randomized Placebo-Controlled Study
PubMed ID: 36596553
Theanine (± arginine) blunted sAA increases after stress tasks vs placebo, showing a balanced physiological stress response.
- Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials
PubMed ID: 30308973
Matcha lowered anxiety and stress biomarker in students under pressure — supports resilience to situational stress.
Relaxation (9)
- L-theanine, a natural constituent in tea, and its effect on mental state
PubMed ID: 18296328
Clear increase in resting EEG alpha at low doses consistent with relaxed alertness (canonical theanine effect).
- Effect of Combined Ingestion of L-Theanine and L-Arginine for Short-Term Psychological Stress in Young Adults: A Randomized Placebo-Controlled Study
PubMed ID: 36596553
Single-dose theanine lowered sAA stress response acutely without sedation measures — physiologic relaxation signal.
- Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials
PubMed ID: 30308973
Theanine‑rich matcha lowered STAI anxiety and salivary amylase versus control, consistent with relaxation.
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
PubMed ID: 21040626
97 mg theanine + 40 mg caffeine increased subjective alertness while improving task accuracy — fits 'alert relaxation' concept (synergy).
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
L-theanine + caffeine reduced anxiety-related state changes in sleep‑deprived adults (implying calming effect).
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Dose-dependent improvements in RT and attention occurred without reported sedation, supporting calm alertness.
- Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study
PubMed ID: 33751906
Acute attentional and working-memory benefits in older adults occurred without chronic cognitive detriment, consistent with non-drowsy relaxation.
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
4-week RCT showed decreased trait anxiety and improved sleep quality consistent with increased relaxation.
- Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
PubMed ID: 26797633
Acute theanine drink reduced subjective stress and lowered cortisol with increased alpha in anxious individuals.
Wellbeing (6)
- Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study
PubMed ID: 35565828
Multi-ingredient product with theanine reduced stress and cold-pain sensitivity, consistent with better subjective well-being.
- [Clinical evaluation of the efficacy of innovative spread of a given fatty acid composition enriched by adaptogens]
PubMed ID: 37801460
Small but significant increase in SAN well-being after a 10-day multi-ingredient product that contained L-theanine.
- Effects of chamomile and -theanine beverage on menstrual pain, menstrual symptoms, mood, and sleep quality in young women experiencing primary dysmenorrhea: A randomized, double-blind, placebo-controlled study
PubMed ID: 41525193
Chamomile+theanine drink markedly reduced menstrual symptoms and improved mood/vigor and daytime function — indicates improved well‑being, but multi-ingredient.
- 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
PubMed ID: 21208586
Augmentation reduced anxiety and some symptoms, likely improving overall wellbeing in clinical group.
- l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 37084960
Adjunctive L-theanine improved depressive symptoms and increased response/remission rates — likely improves overall well‑being in depressed patients.
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
4-week theanine improved mood, sleep quality and verbal fluency — supports improved well-being.
Sleep quality (6)
- Effect of Alpha-S1-Casein Tryptic Hydrolysate and L-Theanine on Poor Sleep Quality: A Double Blind, Randomized Placebo-Controlled Crossover Trial
PubMed ID: 35277011
Cystine+L-theanine (4‑week crossover) increased total sleep time, improved PSQI and increased awake alpha power—objective and subjective sleep benefit (combination product).
- Optimisation and Validation of a Nutritional Intervention to Enhance Sleep Quality and Quantity
PubMed ID: 32854375
Multi‑ingredient drink containing theanine halved sleep onset latency vs placebo, supporting faster sleep initiation.
- Analysis of the Effects of Known Sleep-Support Supplements in Relation to Life Habits, Sleep Conditions, and Sleep Problems
PubMed ID: 37242260
Crossover trial of dietary sleep aids including L-theanine showed within-subject improvements in several self-reported sleep measures and sleep factors (including sleep length/initiation).
- The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 22214254
400 mg/day L-theanine improved objective actigraphy measures (sleep percentage and efficiency) in boys with ADHD.
- L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial
PubMed ID: 30580081
Adjunctive high-dose L-theanine in GAD improved patient-reported sleep satisfaction and subgroup ISI signal (clinical population).
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
4-week 200 mg/day L-theanine RCT significantly improved PSQI total (subjective sleep quality).
Focus & concentration (9)
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Robust improvements in sustained attention and visuomotor RT across doses — directly relevant to concentration for study/work.
- L-theanine, a natural constituent in tea, and its effect on mental state
PubMed ID: 18296328
Resting alpha increases at low dietary doses indicate a relaxed but alert brain state supportive of calm focus.
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
Robust improvements in reaction time, accuracy and ERP (P3b) in sleep-deprived adults with L-theanine+caffeine.
- Matcha consumption maintains attentional function following a mild acute psychological stress without affecting a feeling of fatigue: A randomized placebo-controlled study in young adults
PubMed ID: 33744591
Two‑week matcha preserved attention after stress and improved emotion perception — aids concentration under stress (matrix confound).
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
PubMed ID: 21040626
Approx. 97 mg L-theanine + 40 mg caffeine improved task-switch accuracy and subjective alertness/tiredness.
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Nutrient bar including theanine improved attention and working memory acutely — supports better concentration (co-active confound).
- Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
PubMed ID: 26797633
Reduced stress plus increased alpha (in high‑anxiety individuals) supports calmer attention.
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
Improvements in verbal fluency and decreased trait anxiety support better calm cognitive engagement chronically.
- Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study
PubMed ID: 33751906
Single-dose benefits to Stroop RT and working memory in older adults support concentration improvements.
Memory (6)
- [Clinical evaluation of the efficacy of innovative spread of a given fatty acid composition enriched by adaptogens]
PubMed ID: 37801460
Enriched spread (theanine + others) modestly improved a memory score (Lurie) in a randomized trial.
- Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study
PubMed ID: 33751906
Single-dose theanine improved some working-memory measures acutely in middle-aged/older adults.
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
PubMed ID: 31623400
4-week 200 mg/day L-theanine improved verbal fluency (a memory/executive measure) in an RCT.
- A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study
PubMed ID: 21303262
Green-tea-extract + L-theanine produced modest improvements in delayed recognition and memory measures (esp. impaired subgroup).
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Nutrient bar with 125 mg theanine improved working and episodic memory measures acutely, though other nutrients present.
- Effect of matcha green tea on cognitive functions and sleep quality in older adults with cognitive decline: A randomized controlled study over 12 months
PubMed ID: 39213264
12-month matcha improved emotion-recognition performance (social cognition domain) in older adults with early cognitive decline (theanine-containing product).
Immune support (5)
- Co-administration of l-cystine and l-theanine enhances efficacy of influenza vaccination in elderly persons: nutritional status-dependent immunogenicity
PubMed ID: 19149835
Cystine+theanine markedly raised vaccine seroconversion rates in undernourished elderly subgroups (conditional benefit).
- Perioperative Administration of Cystine and Theanine Suppresses Inflammation and Facilitates Early Rehabilitation and Recovery after Esophagectomy: A Randomized, Double-Blind, Controlled Clinical Trial
PubMed ID: 35684118
Perioperative cystine+theanine reduced inflammatory markers and improved recovery after esophagectomy (randomized double-blind).
- Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial
PubMed ID: 21338496
Green-tea catechins + theanine reduced clinically defined influenza incidence and prolonged time free from illness in healthcare workers (randomized trial).
- Oral administration of the amino acids cystine and theanine attenuates the adverse events of S-1 adjuvant chemotherapy in gastrointestinal cancer patients
PubMed ID: 27306219
Cystine+theanine markedly reduced chemo-associated diarrhea and improved completion rates—strong supportive clinical outcome for resilience.
- Perioperative oral administration of cystine and theanine enhances recovery after distal gastrectomy: a prospective randomized trial
PubMed ID: 22972879
Perioperative cystine+theanine reduced IL-6/CRP and other inflammatory responses after surgery.
Sleep onset (4)
- Analysis of the Effects of Known Sleep-Support Supplements in Relation to Life Habits, Sleep Conditions, and Sleep Problems
PubMed ID: 37242260
Crossover dietary sleep-aid data including L-theanine showed improvements in sleep initiation factors for some participants.
- The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial
PubMed ID: 22214254
Improved sleep efficiency and percentage in ADHD boys suggests easier sleep initiation/maintenance though onset not directly measured.
- Optimisation and Validation of a Nutritional Intervention to Enhance Sleep Quality and Quantity
PubMed ID: 32854375
Optimized multi-ingredient drink including theanine halved sleep onset latency in PSG validation (large objective effect, multi-actives).
- Effect of Alpha-S1-Casein Tryptic Hydrolysate and L-Theanine on Poor Sleep Quality: A Double Blind, Randomized Placebo-Controlled Crossover Trial
PubMed ID: 35277011
CTH + L-theanine increased total sleep time and improved PSQI; onset specifically improved in components (combination product).
Productivity (4)
- Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study
PubMed ID: 33751906
Single-dose theanine sped attention reaction times (~30–40 ms) in middle-aged/older adults (direct acute effect).
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Nutrient bar containing 125 mg theanine improved RVIP speed and accuracy acutely, but multiple co-actives limit attribution.
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
200 mg L-theanine +160 mg caffeine shortened RT (~−38 ms vs placebo) and reduced P3b latency — supports faster RT but includes substantial caffeine.
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Well-powered dose–response crossover showing reliable ~15–20 ms RT speedups (100–400 mg).
Mental clarity (5)
- L-theanine, a natural constituent in tea, and its effect on mental state
PubMed ID: 18296328
50 mg increased EEG alpha activity suggesting a relaxed-but-alert brain state conducive to clarity.
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
Faster reaction times, improved ERP markers and accuracy indicate clearer, faster cognitive processing with theanine+caffeine.
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
PubMed ID: 21040626
Combination (~97 mg theanine + 40 mg caffeine) improved task-switching accuracy and increased subjective alertness/tiredness reduction.
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Improved reaction times and sustained attention across doses support sharper mental performance.
- Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study
PubMed ID: 33751906
Single-dose theanine sped attention and improved working-memory accuracy in older adults (direct evidence for cognitive clarity).
Alertness (4)
- Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
PubMed ID: 26797633
Reduced subjective stress with preserved cognition (MEG alpha increases in anxious subgroup) suggests calm alertness.
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Dose–response RT and sustained-attention improvements without impairment of inhibitory control — supports alert, non-sedated state.
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
PubMed ID: 21040626
Participants reported increased alertness and reduced tiredness with theanine+caffeine.
- L-theanine, a natural constituent in tea, and its effect on mental state
PubMed ID: 18296328
50 mg L-theanine increased EEG alpha consistent with relaxed alertness.
Learning (3)
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
Reduced P3b latency and improved accuracy with theanine+caffeine are consistent with faster stimulus evaluation and smoother switching demands.
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Sustained-attention improvements could modestly support task-switching efficiency, though inhibition was unchanged.
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
PubMed ID: 21040626
Combination produced statistically robust task-switching accuracy improvements in a reasonably sized sample.
Energy & Fatigue (4)
- High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study
PubMed ID: 40789769
Improved attention and reaction times under sleep deprivation indicate maintained cognitive energy; evidence is for combo with caffeine.
- Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study
PubMed ID: 36263942
Improved sustained-attention reaction times imply reduced task-related fatigue; measured acutely.
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Nutrient bar containing theanine produced immediate improvements in attention and alertness, consistent with steadier cognitive energy (multi‑nutrient product).
- The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
PubMed ID: 21040626
Subjects reported reduced tiredness with theanine+caffeine alongside task-switch improvements.
Similar by evidence
Supplements the same benefits carry qualifying findings for — a fact about the evidence graph, not a recommendation to swap.
Products with Theanine
Search all6842 products whose verified label declares Theanine — not every bottle that mentions it in a title.
Being studied right now
Recruiting clinical trials registered on ClinicalTrials.gov. A trial in progress has no result yet — this is what the field is asking, not what it found.