L-Theanine Research
L-theanine is a unique amino acid found primarily in tea leaves that promotes relaxation without sedation. It's known for its ability to reduce stress and anxiety while improving focus, often taken with caffeine for synergistic cognitive benefits. Over 150 studies have examined its effects on stress, attention, and sleep.
Last updated: October 31, 2025
Key Research Findings
Acute stress and anxiety reduction
✓✓✓ Strong EvidenceMultiple double-blind studies demonstrate L-theanine (200mg) significantly reduces subjective stress and anxiety within 30-60 minutes. EEG studies show increased alpha brain wave activity associated with relaxed alertness.
Enhanced focus and attention with caffeine synergy
✓✓✓ Strong EvidenceL-theanine combined with caffeine produces superior cognitive benefits compared to either compound alone. Studies show improved accuracy, alertness, and reduced jitters from caffeine when combined with L-theanine.
Improved sleep quality without sedation
✓✓ Moderate EvidenceUnlike sedatives, L-theanine improves sleep quality by reducing anxiety and promoting relaxation without causing drowsiness during the day. Studies show improvements in sleep efficiency and reduced sleep disturbances.
Featured Clinical Studies
L-theanine reduces stress and improves cognitive performance under stress
Key Finding: 200mg L-theanine significantly reduced heart rate and salivary immunoglobulin A responses to acute stress
Caffeine and L-theanine combination improves cognitive performance
Key Finding: Combination improved speed and accuracy of attention tasks and reduced susceptibility to distracting information
How It Works
GABA Modulation
L-theanine increases GABA, serotonin, and dopamine levels in the brain, promoting relaxation and mood improvement without sedation.
Alpha Brain Wave Activity
Increases alpha brain wave activity within 30-45 minutes, associated with wakeful relaxation and creative thinking.
Glutamate Receptor Antagonism
Structurally similar to glutamate, L-theanine may act as a mild antagonist at glutamate receptors, reducing excitatory signaling.
Caffeine Modulation
Reduces jitteriness and anxiety from caffeine while preserving alertness, creating smoother, more focused energy.
Safety & Side Effects
Overall Safety Assessment
Excellent safety profile with no significant side effects reported at standard doses (100-400mg daily). Generally recognized as safe (GRAS) by FDA.
⚠️Common Side Effects
- •Virtually no side effects at recommended doses
- •Mild relaxation or drowsiness at very high doses (>600mg)
- •Rare reports of headache (typically at doses >400mg)
🚫Contraindications
- •Pregnancy/breastfeeding (insufficient safety data)
- •Severe hypotension (low blood pressure)
Important Safety Considerations
Blood pressure effects
May slightly lower blood pressure. Generally beneficial, but those with hypotension should monitor.
Minimal concernResearch-Based Dosage
stress anxiety
100-200mg as needed, or 1-2 times daily
with caffeine
100-200mg L-theanine per 100mg caffeine (2:1 or 1:1 ratio)
sleep support
200-400mg, 30-60 minutes before bed
daily cognitive support
100-200mg, 1-2 times daily
timing
Fast-acting (30-60 minutes). Can be taken with or without food.
forms
Pure L-theanine powder or capsules. Naturally found in green tea (20-50mg per cup).
Medical Disclaimer
This information is for educational purposes only and is not intended as medical advice. The research presented here is compiled from peer-reviewed sources but should not replace consultation with a qualified healthcare professional. Always consult your doctor before starting any new supplement regimen, especially if you have existing health conditions or take medications.