Research Vault / Nutrients
Nutrients · Evidence guide
L-Theanine Evidence Guide
An amino acid found in tea, studied for stress-related and cognitive outcomes.
Reviewed October 1, 2026 · Sources linked below
How it works
Neurotransmission and stress-response pathways are under investigation. Proposed brain effects should not be treated as a demonstrated treatment mechanism.
01Tea amino acid
02Neural signaling research
03Small human studies
Simplified mechanism map. It does not represent a proven treatment outcome.
What the evidence can tell us
A small randomized crossover trial in 30 adults explored stress symptoms and cognition over four weeks. Its findings do not establish treatment for an anxiety disorder or reliable effects in everyone.
Safety and important limits
Long-term and combination safety evidence is limited. Review supplements with a clinician when taking medicines or managing a health condition.
This is a learning guide, not a recommendation to begin a supplement. Baseline nutrition, medicines and health conditions affect what is appropriate.