L-theanine
⤢ 3D
L-theanine is an amino acid found in tea that promotes relaxation without sedation, partly by modulating alpha brain-wave activity and calming glutamatergic tone. The best evidence is for combining it with caffeine to improve attention and reduce jitteriness; effects on anxiety and sleep are modest. It has a strong safety profile.
Too little may be associated with
No deficiency state.
Too much may be associated with
Generally well tolerated; mild drowsiness.
Informational only — not medical advice.
Neurotransmitters
Hormones
Related
Where to buy
Popular L-theanine products on Amazon. Not medical advice — talk to a clinician before starting a supplement.
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Research (7)
- Nutritional co-therapy with vitamin D and L-theanine reduces unpredictable mild chronic stress (UCMS) in aged mice by restoring alpha-oscillations, dopamine levels and behavioral improvement Hussain et al. (2025) Full text ↗ 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 ↗
- The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review Anas et al. (2021) 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 ↗
- L-Theanine reduces psychological and physiological stress responses Ozeki et al. (2007) PubMed ↗
- Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans Abdou et al. (2006) Full text ↗ PubMed ↗
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