L-Theanine
Amino acid from tea that research indicates may promote relaxation and cognitive performance without sedation.
Human Trials
18
1,247 participants
Risk Level
Monthly Cost
Based on 100-200mg daily dosing
Quick Facts
- Category
- Supplement
- Research Field
- Supplements
- Evidence Grade
- B+ – Good
- Risk Level
- Low
- Monthly Cost
- $8 – $25
- Human Trials
- 18
Typical Dose
100–200 mg
Range
50–400 mg
For informational purposes only – not medical advice. See disclaimer
Research Velocity
Mechanism of Action
L-theanine crosses the blood-brain barrier and increases alpha brain wave activity, which is associated with relaxed alertness. It modulates neurotransmitter levels including GABA, dopamine, and serotonin, while also blocking glutamate receptors. Research suggests it may reduce cortisol levels and promote a calm but focused mental state without causing drowsiness.
Overview
L-theanine is an amino acid naturally found in tea leaves, particularly green tea, that research indicates may promote relaxation without sedation. Studies suggest it can reduce stress markers including cortisol and blood pressure while enhancing alpha brain wave activity associated with calm alertness. Multiple human trials have demonstrated its potential to reduce anxiety and improve cognitive performance, particularly when combined with caffeine.
Research indicates L-theanine may be particularly beneficial for managing stress-related cognitive impairment and promoting focused relaxation. Clinical studies suggest typical effective doses range from 100-200mg daily, with effects typically observed within 30-60 minutes of consumption. The compound appears to have excellent safety profile with minimal reported side effects in healthy adults.
While naturally occurring in tea, therapeutic doses typically require supplementation as a cup of green tea contains only 5-8mg of L-theanine. Studies suggest it may be especially useful for individuals seeking cognitive enhancement without stimulant-related side effects, or those looking to moderate caffeine's anxiety-inducing properties while maintaining its cognitive benefits.
Known Interactions
- May enhance effects of blood pressure medications
- Can potentiate sedative effects of CNS depressants
- May interact synergistically with caffeine for cognitive benefits
Legal Status by Country
Your country (United States)
Available without prescription in:
Australia, Brazil, Canada, China, Colombia, Germany, India, Israel, Japan, Mexico, Netherlands, Panama, Russia, South Korea, Switzerland, Thailand, Turkey, UAE, United Kingdom, United States
📍 = your selected country · ✈️ = medical tourism destination · Always verify current local regulations before travel.
Key Research
- 2019
Primary stress reduction study
- 2008
Anxiety comparison trial
- 2011
Comprehensive review of cognitive effects
- 2008
Cognitive enhancement study
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Last verified: 2026-03-16