Green Tea
A source of L-theanine and catechins (notably EGCG), associated with calm alertness and antioxidant activity.
Benefits
Source of catechins (EGCG) and L-theanine linked to alert-but-calm focus and metabolic and cardiovascular benefits.
Risks
Contains caffeine (sleep/anxiety effects); concentrated extracts have caused rare liver injury and can reduce iron absorption.
Informational only — not medical advice.
Body systems
Organs
Functions
Neurotransmitters
Related
Where to buy
Popular Green Tea products on Amazon. Not medical advice — talk to a clinician before starting a supplement.
As an Amazon Associate, Neurotransmission earns from qualifying purchases.
Research (22)
- Natural anti-cancer products: insights from herbal medicine Zhang et al. (2025) PubMed ↗
- 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) Full text ↗ PubMed ↗
- Epigallocatechin Gallate (EGCG): Pharmacological Properties, Biological Activities and Therapeutic Potential Capasso et al. (2025) PubMed ↗
- Health-Related Messages About Herbs, Spices, and Other Botanicals Appearing in Print Issues and Websites of Legacy Media: Content Analysis and Evaluation Gaba et al. (2024) Full text ↗ PubMed ↗
- Safety and Effectiveness of Oral Nutraceuticals for Treating Acne: A Systematic Review Shields et al. (2023) PubMed ↗
- Green Tea Catechins Attenuate Neurodegenerative Diseases and Cognitive Deficits Afzal et al. (2022) Full text ↗ PubMed ↗
- Green Tea (Camellia sinensis): A Review of Its Phytochemistry, Pharmacology, and Toxicology Wang et al. (2022) PubMed ↗
- Dietary supplements for obesity Bonetti et al. (2022) PubMed ↗
- The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review Anas et al. (2021) Full text ↗ PubMed ↗
- Warfarin and food, herbal or dietary supplement interactions: A systematic review Tan et al. (2021) PubMed ↗
- Health Benefits and Chemical Composition of Matcha Green Tea: A Review Kochman et al. (2020) PubMed ↗
- GABA-enriched teas as neuro-nutraceuticals Hinton et al. (2020) Full text ↗ PubMed ↗
- GABA and l-theanine mixture decreases sleep latency and improves NREM sleep Kim et al. (2019) Full text ↗ PubMed ↗
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial Hidese et al. (2019) PubMed ↗
- Tea Polyphenols in Promotion of Human Health Khan et al. (2018) PubMed ↗
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