Clinical ResearchResearch compound

L‑Theanine

Green tea amino acid, γ-glutamyl-ethylamide, α-wave enhancer.

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WHAT IS L-THEANINE?

Detailed overview

L-Theanine (N-ethyl-L-glutamine, γ-glutamyl-ethylamide) is a free amino acid, the main non-protein amino acid component of Camellia sinensis (green tea) leaves. It crosses the blood-brain barrier (Tmax ~50 min) and enhances EEG α-wave activity in the relaxed-awake state (Nobre 2008, PMID 18296328). **Combined with caffeine (the classical L-theanine:caffeine 2:1 or 200 mg:100 mg protocol)** it synergistically improves attention (Foxe 2012, PMID 22849538) and reduces caffeine-induced vasoconstriction + anxiety. A single 200-400 mg dose can ease the stress response in healthy adults. **Does NOT produce sedation** or dependence – one of the safest anxiolytic nootropics. Also studied in pediatric ADHD syndrome (Lyon 2011 – improved sleep quality in boys). FDA GRAS.

Mechanism

GABA + α-wave + glutamate modulation

Onset

30-45 min oral

Legal status

OTC food + dietary supplement

Safety

Side effects, stop signs, contraindications

Side effects · 5

  • Headache, mainly at higher (>400 mg) doses
  • Mild dizziness or lightheadedness in sensitive individuals
  • Mild drowsiness or sedation at larger doses
  • Mild GI upset or nausea on an empty stomach
  • Slight lowering of blood pressure

Contraindications · 5

  • Antihypertensive medication, due to additive blood-pressure-lowering effect
  • Pre-existing low blood pressure, caution advised
  • Sedatives or CNS depressants, additive sedation possible
  • May blunt the effect of stimulants when taken together
  • Pregnancy and breastfeeding, due to insufficient safety data

Related Nootropics

Same therapeutic category

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MolekulaX Editorial Team·Source-verified · PubMed · FDA · EMA
Updated: June 19, 2026

The information here is strictly for educational and scientific purposes. It does not replace medical advice or clinical consultation, and it does not encourage illegal substance or pharmaceutical use. Data is sourced. When in doubt, consult your doctor.