L-theanine
What L-theanine from the tea leaf is, how much a capsule holds, why it is often paired with caffeine and how to read the label.
This substance has no health claim authorised in the European Union. So we describe what it is and how it is taken, but do not say what it does in the body.
What it is
L-theanine is an amino acid found in nature almost only in tea leaves (Camellia sinensis); it gives green tea much of its characteristic umami taste. A cup of tea usually holds 8–30 mg. For supplements theanine is made by fermentation; Suntheanine is a brand of such theanine.
No claims about what L-theanine does are authorised in the European Union, so we do not write about calm, focus or sleep; we describe the substance and the products.
How to read the label
Capsules usually hold 100–200 mg of L-theanine. It is often paired with caffeine in one capsule, usually 2:1 (say 200 mg theanine and 100 mg caffeine), and added to "night" complexes with magnesium. If a product contains caffeine, its page shows the mandatory warning with the amount.
How it is taken
Take as the pack directs. Theanine products are not recommended for pregnant or breastfeeding women or children. People on blood-pressure medicines or sedatives should ask a doctor first.
Frequently asked questions
How much theanine is in a cup of green tea?
Usually 8–30 mg, depending on the tea and how it is brewed. A supplement capsule holds 100–200 mg.
Why is theanine paired with caffeine?
It is a popular recipe among makers, echoing how the two occur together in tea. We show the contents and the caffeine warning but claim no effect.
What is Suntheanine?
A brand of L-theanine made by fermentation. It is the same substance, purity-controlled.
Other amino acids in the shop
