L-Theanine
An amino acid found in tea (camellia sinensis) that promotes a calm, focused state — most often used to take the edge off caffeine.
Why it matters
L-theanine increases alpha brainwave activity and modulates glutamate and GABA signalling. Studies in humans show reductions in self-rated stress and improvements in attention measures, particularly when combined with caffeine. The compound is non-sedating; it is the “calm focus” half of the caffeine + theanine pairing.
In practice
Typical doses are 100–200mg. Combined with caffeine in a 2:1 theanine:caffeine ratio is the canonical stack; many “focus” supplements are essentially codified versions of that combination.
Common confusion
“L-theanine cures anxiety” is wrong — the effect is real but modest, and the mechanism is gentle modulation rather than direct anxiolysis.
This glossary entry is editorial content reviewed against primary sources. It is not medical advice. See our Editorial Policy.
