L-Theanine
Amino acid found in tea leaves, commonly used for relaxation without drowsiness.
Also known as Theanine, L Theanine
Common doses
100-200 mg
Best timing
Any time
Food
With or without food
Interactions
2 known
L-theanine is an amino acid found almost exclusively in tea leaves (Camellia sinensis). It crosses the blood-brain barrier and promotes a state of relaxed alertness by increasing alpha brain wave activity, which is associated with calm focus and creativity.
L-theanine's most popular application is in combination with caffeine. It is the reason why tea produces a calmer, more focused stimulation than coffee, despite both containing caffeine. As a supplement, the caffeine + L-theanine stack is one of the most well-studied nootropic combinations.
L-theanine also modulates neurotransmitters including GABA, serotonin, and dopamine, though its effects are subtle and non-sedating at typical doses. It reduces the physiological stress response (cortisol, heart rate) without causing drowsiness.
Key benefits
Relaxed focus
L-theanine increases alpha brain wave activity within 30-40 minutes, producing a calm but alert mental state without sedation.
Caffeine synergy
Combined with caffeine, L-theanine improves attention and task-switching while reducing caffeine-related jitteriness and anxiety.
Stress reduction
L-theanine reduces the cortisol and heart rate response to acute stress without sedation or impaired performance.
Sleep quality
At higher doses (200-400 mg), L-theanine may improve sleep quality, not by sedation but by reducing pre-sleep anxiety.
Available forms
L-Theanine (Standard)
Pure L-theanine. Typically 100-200 mg per dose. Can be taken as capsules or powder. Slightly sweet taste.
Suntheanine
Patented form produced by enzymatic fermentation. 100% L-isomer (some generic products contain D-theanine). The most clinically studied brand.
Food sources
- Green tea
- Black tea
- White tea
- Matcha (highest per serving)
Upper intake limit
No established upper limit. Doses up to 900 mg/day have been used in studies without adverse effects. Standard dose is 100-200 mg.
Research summary
Good evidence for alpha brain wave promotion and stress reduction. Strong evidence for the caffeine + L-theanine combination for attention and focus. Moderate evidence for sleep quality improvement. One of the safest nootropics available with no known side effects at standard doses.
Known interactions (2)
Check your full stack
for interactions.
See what competes, what combines well, and when to take everything. Every interaction cites a published source.
Stack
6 supplements
Stack review
1 flagZinc and Iron compete for the same absorption pathway. Take at least 2 hours apart.
Supplements
This information is for educational purposes only. It is not medical advice and does not diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional.