L-Theanine
An amino acid found in tea leaves, associated with a state of relaxed alertness. Studied for reducing stress and supporting a calmer transition to sleep.
- Common timing: Evening / with caffeine
- Evidence strength: Emerging / early
What L-theanine is
L-theanine is an amino acid found almost exclusively in tea (and some mushrooms). It's thought to increase calming brain activity and influence neurotransmitters like GABA, serotonin, and dopamine — producing a state people often describe as 'relaxed but alert.' It's the reason a cup of tea can feel calming despite its caffeine.
What the evidence says
Research is still early but encouraging. Small studies suggest L-theanine may reduce stress and anxiety markers and support relaxation, which can indirectly make it easier to fall asleep. Unlike sedatives, it doesn't appear to cause grogginess. It's sometimes paired with caffeine to blunt jitters while keeping focus.
Safety
L-theanine is generally well-tolerated with few reported side effects, and you already consume it any time you drink tea. As with any supplement, quality and dosing vary, and it's wise to check with a professional if you take medications or are pregnant.
References
- Hidese S, et al. Effects of L-Theanine on stress-related symptoms. Nutrients. 2019.
- Williams JL, et al. The effects of L-theanine on mental health. Plant Foods Hum Nutr. 2020.
L-Theanine: FAQ
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