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L-theanine
Also called: theanine
An amino acid found in tea leaves.
- Why people take it
- Calm focus, stress and sleep, often taken with caffeine.
- What the evidence says
- Small studies suggest it may help relaxation and attention, especially with caffeine, but good-quality evidence is limited.
- Be careful
- Usually well tolerated. Talk to your doctor if you take blood-pressure medicines or sedatives.
- In food
- Green and black tea.
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Common questions
What is L-theanine?
An amino acid found in tea leaves.
Why do people take L-theanine?
Calm focus, stress and sleep, often taken with caffeine.
Does L-theanine work?
Small studies suggest it may help relaxation and attention, especially with caffeine, but good-quality evidence is limited.
Is L-theanine safe?
Usually well tolerated. Talk to your doctor if you take blood-pressure medicines or sedatives.
Sources and further reading
Last reviewed 31 October 2026. Written by Satya Babu.
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