SupplementsAmino acidsCalmFocus
L-theanine is the amino acid that gives green tea its smooth character. It promotes a relaxed-but-alert state without sedation.
Key takeaways
- ~200 mg L-theanine promotes calm alertness without drowsiness.
- In a controlled trial it reduced stress-related symptoms and improved executive function and verbal fluency.1
- It pairs well with caffeine, smoothing the jitters while keeping the focus.
- Very safe and non-habit-forming.
What it is
L-theanine is a non-protein amino acid unique to tea. It influences alpha brain-wave activity and calming neurotransmitters, producing relaxation without sedation.
The evidence
A randomised trial giving 200 mg/day for four weeks found improvements in stress-related scores (anxiety, sleep quality) and in verbal fluency and executive function in healthy adults.1 Acute doses also aid attention, especially with caffeine.
Dose & how to use
100–200 mg as needed, or paired with caffeine (a common ~1:2 caffeine:theanine ratio) for focus.
Safety & who benefits
Very safe. Most useful for stress, focus, and taking the edge off caffeine.
References
Adult research summary for education, not a prescription. These are food supplements, not treatments for disease.
- Hidese S, et al. Effects of L-Theanine on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients 2019. pmc.ncbi.nlm.nih.gov
This article summarises nutrition and exercise science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.