Ingredients / Focus & brain

L-theanine

What it is

An amino acid found mainly in tea leaves, with small amounts in a few other plants and some mushrooms. It is also made synthetically for supplements and drinks.

Why it is in energy drinks

Often paired with caffeine and marketed for calmer focus or fewer jitters.

Worth knowing

Small studies of caffeine plus L-theanine on attention exist, but the results are modest and not settled.

General information, not medical advice. We read what the label lists and don't test what an ingredient does.