L-Theanine
The calming amino acid from green tea — promotes relaxation without drowsiness.
Also known as: Theanine • Gamma-glutamylethylamide • Suntheanine
Overview
L-Theanine is a unique amino acid found almost exclusively in tea leaves (Camellia sinensis), particularly green tea. It crosses the blood-brain barrier and promotes a state of calm, focused alertness by increasing alpha brain wave activity — the same brain wave pattern associated with meditation. Unlike most calming supplements, L-theanine doesn't cause drowsiness, making it ideal for daytime use. It's particularly popular when combined with caffeine, where it smooths out caffeine's jittery effects while preserving the focus and energy benefits.
Key Benefits
Calm Focus Without Drowsiness
L-Theanine increases alpha brain wave activity within 30–40 minutes of ingestion. Alpha waves are associated with a state of relaxed alertness — the same state achieved during meditation. This makes it unique among calming supplements.
Caffeine Synergy
The L-theanine + caffeine combination is one of the most well-studied nootropic stacks. L-theanine smooths out caffeine's jittery effects, reduces anxiety, and enhances the focus-promoting benefits. A typical ratio is 2:1 (200mg theanine to 100mg caffeine).
Stress & Anxiety Reduction
L-Theanine reduces cortisol and subjective stress without sedation. A study found that 200mg reduced stress response and heart rate during a challenging cognitive task.
Sleep Quality Improvement
While not a sedative, L-theanine at 200–400mg before bed improves sleep quality by promoting relaxation and reducing racing thoughts. It's particularly helpful for people whose sleep issues stem from an overactive mind.
Dosage & How to Take
Standard dose is 100–200mg for focus and stress relief, 200–400mg for sleep support.
| Purpose | Dose | Notes |
|---|---|---|
| Calm focus | 100–200 mg | Can be taken multiple times daily |
| With caffeine | 200 mg + 100 mg caffeine | 2:1 ratio is optimal |
| Stress relief | 200 mg | As needed; effects within 30 minutes |
| Sleep support | 200–400 mg | 30–60 minutes before bed |
Best Time to Take
Effects felt within 30–40 minutes; lasts 4–6 hours
With or Without Food
Can be taken with or without food
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| Suntheanine | Excellent | All purposes | Patented pure L-isomer; most studied form; enzymatically produced |
| Standard L-Theanine | Good | Budget option | May contain D-theanine isomer; still effective |
| Green tea extract | Good | Natural source with other tea compounds | Contains caffeine and catechins along with theanine |
Side Effects & Safety
Common
- Generally very well tolerated
- Rare: mild headache
Rare
- Dizziness at very high doses
- GI discomfort
Contraindications
- None known at standard doses
- Caution with blood pressure medications (may lower BP slightly)
Interactions
Synergistic — enhances focus while reducing jitteriness
May slightly enhance blood pressure lowering
May modulate stimulant effects
Scientific Research
L-Theanine and Alpha Waves
200mg L-theanine significantly increased alpha brain wave activity within 40 minutes
Theanine + Caffeine Combination
The combination improved attention, task switching, and reduced susceptibility to distraction
L-Theanine and Stress
200mg reduced cortisol and heart rate response to acute stress
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.