Clinical Studies on L-Theanine

L-Theanine (400mg) 

L-Theanine is a naturally occurring amino acid found in tea, known for supporting normal relaxation without drowsiness by influencing brain wave activity (such as alpha waves) and normal levels of neurotransmitters like GABA, serotonin, and dopamine.*

Summary of Research on L-Theanine 

Research has explored L-theanine's role in supporting normal physiological processes related to relaxation, mood balance, restful sleep, cognitive function, and everyday resilience. Key areas of study include:

General Nervous System Support

• Studies indicate that L-theanine supports normal central nervous system activity and contributes to everyday relaxation and balance.*

• Link: [Neurobiological effects of theanine and its possible use in neurology and psychiatry] (Katasonov, 2018)

Relaxation and Everyday Stress Response

• Investigations have assessed L-theanine's effects on normal responses to everyday challenges or mental tasks, noting support for healthy relaxation and adaptive markers.*

• Examples include studies using controlled tasks to evaluate subjective calm and physiological indicators in healthy adults.*

• Links:

The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review (Williams et al., 2020)

Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial (Hidese et al., 2019)

Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia (Sakamoto et al., 2019)

Effect of Green Tea Phytochemicals on Mood and Cognition (Dietz et al., 2017)

Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial (White et al., 2016)

(PDF) Theanine consumption, stress and anxiety in human clinical trials: A systematic review (Everett et al., 2015)

Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stress (Unno et al., 2013)

Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses (Yoto et al., 2012)

L-theanine, a natural constituent in tea, and its effect on mental state (Nobre et al., 2008)

L-Theanine reduces psychological and physiological stress responses (Kimura et al., 2007)

Effects of L-Theanine on the Release of α-Brain Waves in Human Volunteers (Kobayashi et al., 1998)

Mood and Emotional Well-Being

• Research has examined L-theanine’s influence on normal mood pathways and emotional balance in healthy adults under typical daily conditions.*

  • Links:

  • The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review (Moshfeghinia et al., 2024)

  • l-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial (Shamabadi et al., 2023)

  • Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study (Hidese et al., 2017)

Restful Sleep Patterns

• Some research has evaluated L-theanine’s support for normal sleep architecture and restful patterns in healthy individuals or those with occasional sleep disruptions.*

  • Examples include trials assessing sleep parameters and overall restfulness.*

  • Links:

  • The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis (Bulman et al., 2025)

  • 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 et al., 2024)

  • An Exploratory Study to Detect the Effects of the Combined Intake of Gamma-aminobutyric Acid (GABA) and L-theanine on Sleep by Wearable Device (Konno et al., 2023)

  • Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial (Hidese et al., 2019)

  • In Search of a Safe Natural Sleep Aid (Rao et al., 2015)

  • (PDF) 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 (Lyon et al., 2011)

Cortisol Balance & Healthy Stress Response

• Studies have investigated L-theanine’s support for normal cortisol regulation and the body’s adaptive response to everyday stressors.*

  • Examples include trials observing hormonal and physiological markers in healthy adults.*

  • Links:

  • Effects of supplement L-theanine on cognitive anxiety, salivary alpha-amylase, and cortisol in archery competition (Lim, 2024)

  • 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 et al., 2021)

  • Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial (White et al., 2016)

Cognitive Function and Mental Clarity

• Research has explored L-theanine’s potential to support normal cognitive processes, attention, memory, and mental performance under everyday demands.*

  • Examples include assessments of cognitive tasks and executive function in healthy adults.*

  • Links:

  • 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 et al., 2025)

  • The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review (Moshfeghinia et al., 2024)

  • L-theanine improves neurophysiological measures of attention in a dose-dependent manner: a double-blind, placebo-controlled, crossover study (Dassanayake et al., 2022)

  • The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review (Sohail et al., 2021)

  • Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study (Baba et al., 2021)

  • Effects of l-theanine–caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT (Kahathuduwa et al., 2020)

  • Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial (Hidese et al., 2019)

  • l-Theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging study (Kahathuduwa et al., 2018)

  • Green tea effects on cognition, mood and human brain function: A systematic review (Mancini et al., 2017)

  • Acute effects of theanine, caffeine and theanine-caffeine combination on attention (Kahathuduwa et al., 2017)

  • Neurobiological effects of the green tea constituent theanine and its potential role in the treatment of psychiatric and neurodegenerative disorders (Lardner, 2014)

  • 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 (Park et al., 2011)

  • The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness (Giesbrecht et al., 2010)

  • The deployment of intersensory selective attention: a high-density electrical mapping study of the effects of theanine (Gomez-Ramirez et al., 2007)

Neuroprotection

• Some research has examined L-theanine’s support for normal brain function and cellular protection in healthy models.*

  • Examples include preclinical and exploratory studies on normal neuroprotective pathways.*

  • Links:

  • L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications (Li et al., 2022)

  • Neuroprotective attributes of L-theanine, a bioactive amino acid of tea, and its potential role in Parkinson's disease therapeutics (Deb et al., 2019)

  • l-Theanine: An astounding sui generis integrant in tea (Sharma et al., 2018)

  • Neuroprotective Effects and Mechanisms of Tea Bioactive Components in Neurodegenerative Diseases (Chen et al., 2018)

  • Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction (Kakuda, 2011)

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. The summaries above reference general research on L-theanine and do not represent specific claims about NeuroVital Serenity. Consult a healthcare professional before use, and see full studies for details.