L-Theanine
Also known as: theanine, suntheanine, γ-glutamylethylamide
Recommended Dosage
100–400 mg
L-Theanine is an amino acid found almost exclusively in tea leaves (Camellia sinensis). It promotes a state of calm alertness by increasing alpha brain wave activity — the same pattern seen during meditation. When combined with caffeine, it creates a synergistic effect: sustained attention and focus without the jitteriness or crash of caffeine alone. This makes the L-Theanine + caffeine stack one of the most well-validated nootropic combinations.
TL;DR: Amino acid from green tea. Promotes calm focus (alpha brain waves) without drowsiness. Excellent safety profile.
Quick Facts
Evidence
Grade B
Studies
3
Interactions
2
Forms
2
Evidence Rating: Grade B — Moderate Evidence
Some RCTs with positive results, or strong observational evidence. More research may refine our understanding.
Forms Comparison
Standard L-Theanine
✓ High AbsorptionEffective and well-studied form derived from green tea. Works well for most users.
Suntheanine (enzymatically produced)
✓ High AbsorptionPatented form produced via enzymatic fermentation. Pure L-isomer with the most clinical trial data.
Interaction Warnings
May enhance BP lowering effects slightly
Theanine may blunt some stimulant effects
Important Notes
- Very well tolerated
- Synergistic with caffeine for focus without jitters
- Not sedating; does not impair driving
Clinical Evidence (3 studies)
L-theanine and caffeine improve cognitive performance
Nobre AC et al. (2008) — Asia Pac J Clin Nutr
L-theanine and caffeine improve cognitive performance and increase alertness
View on PubMedL-theanine reduces psychological and physiological stress
Kimura K et al. (2007) — Biol Psychol
L-theanine reduces stress responses
View on PubMedTheanine + caffeine improve attention-switching
Owen GN et al. (2008) — Nutr Neurosci
Improved speed and accuracy on attention-switching tasks
View on PubMedAlternatives to Consider
These supplements target similar goals and may be worth considering alongside or instead of L-Theanine.
Bacopa Monnieri
Grade BAyurvedic herb with strong meta-analytic evidence for memory and learning. Requires consistent use for 8-12 weeks.
Phosphatidylserine
Grade BPhospholipid that supports cell membrane integrity in the brain. FDA-qualified health claim for cognitive decline. Reduces cortisol.
L-Tyrosine
Grade BAmino acid precursor to dopamine, norepinephrine, and thyroid hormones. Best evidence is for maintaining cognitive performance under stress, sleep deprivation, and multitasking. Take on empty stomach.
Related Supplements
Bacopa Monnieri
Grade B — Moderate EvidenceAyurvedic herb with strong meta-analytic evidence for memory and learning. Requires consistent use for 8-12 weeks.
Phosphatidylserine
Grade B — Moderate EvidencePhospholipid that supports cell membrane integrity in the brain. FDA-qualified health claim for cognitive decline. Reduces cortisol.
L-Tyrosine
Grade B — Moderate EvidenceAmino acid precursor to dopamine, norepinephrine, and thyroid hormones. Best evidence is for maintaining cognitive performance under stress, sleep deprivation, and multitasking. Take on empty stomach.
Magnesium L-Threonate
Grade B — Moderate EvidenceThe only magnesium form shown to cross the blood-brain barrier effectively. Promising for cognitive function and brain aging.
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⚕️ Important Disclaimer
This information is for educational purposes only. It is not medical advice. Always consult a healthcare provider before starting any supplement regimen, especially if you take medications or have health conditions.
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