Supports cognitive function*

Supports relaxed mood*

Supports stress resilience*

Supports sleep*

Supports general immune health*


L-theanine is a calming amino acid that naturally occurs in green tea. It is used as a nootropic because it supports focused attention, mental alertness, and a calm, relaxed sense of mental energy. L-theanine is often used with caffeine in nootropic stacks, because the combination supports task switching, accuracy, and focus. L-theanine promotes alpha brain waves (α-waves), which are thought of as a marker of relaxation [1]. This brain state also reduces the perception of stress. L-theanine has a few other lesser-known functional actions. L-theanine can be broken down into glutamate, which is a building block for glutamatergic signaling (i.e., the glutamate-GABA pathway) and for glutathione, an antioxidant used for detoxification. And L-theanine, because of another metabolite, primes specialized immune cells—gamma delta T cells—that help the immune system respond more efficiently to new antigens and have enhanced immune memory.* The best dietary sources of L-theanine are green and black tea (made from Camellia sinensis): L-theanine comprises up to 50% of total amino acids in tea leaves.


L-theanine is non-GMO, gluten-free, and vegan.


L-theanine has been studied clinically over a fairly wide range of servings, with the most common range being 100-400 mg. Evidence suggests a threshold response (see Neurohacker Dosing Principles) when L-theanine is given by itself (i.e., much of the benefits occur within the lower end of the serving range). That said, the serving of L-theanine used in a Neurohacker formulation can vary significantly depending upon what other ingredients it’s combined with and the intent of the formulation. Neurohacker looks for additive or complementary ingredient combinations. In some cases, ingredients tend to be most complementary when used at certain ratios. L-theanine falls into this category. As an example, when used as part of a nootropic formula combined with a source of caffeine, the serving of L-theanine might be chosen to provide about double the amount of caffeine and/or theobromine (i.e., ~2:1 ratio). But when used in combination with GABA before bedtime for supporting sleep, the serving might be as little as 20% of the GABA amount (i.e., 1:5 ratio). Following oral intake, the amount of L-theanine in the brain increase within the first hour (i.e., it’s able to cross the blood-brain barrier [2], so in general, L-Theanine has a fairly quick onset and is often experienced within 30-45 minutes of taking it.*



Supports brain function*

Supports attention* [3–5]

Supports memory and learning* [4–7]

Supports executive function* [4,8]

Supports faster reaction times* [3]

Supports alpha (α) brain waves (α-waves are associated with relaxation, selective attention, and mental alertness)* [1,3,9–12]

Supports hippocampal activity* [13]

Supports dopamine signaling* [14–20]

Supports serotonin signaling* [20]

Supports GABA signaling* [20]

Binds to glutamate receptors (with low affinity)* [21–23]

Supports hippocampal neurogenesis (in animals)* [6]

Supports brain-derived neurotrophic factor (BDNF) levels* [6,23,24] 

Supports neuroprotective functions* [7,25–28]

Supports healthy mood and stress responses*

Supports a calm/relaxed mood* [4,8,12,13,25,29–32]

Supports a positive mental-emotional bias* [4,8]

Supports psychological and physiological stress responses* [33]

Supports healthy behavioral and cognitive responses to stress* [26,34]

Reduces fight or flight nervous system activity (i.e., promotes relaxation response)* [33]

Supports sleep*

Supports sleep efficiency and quality* [4,8,35,36]

Counters some of caffeine’s effects on deep sleep* [37]

Supports healthy immune function*

Supports general immune health* [38–40]

Supports post-exercise immunity* [41–44]

Supports innate immunity* [42,45,46]

Supports adaptive immunity* [42,46,47]

Supports immune signaling* [42,48]

Supports healthy immune cell function [41–46,49–54]

Supports healthy gastrointestinal function*

Supports a healthy gut microbiota* [55]

Supports amino acid absorption* [56]

Complementary ingredients*

Caffeine for cognitive performance* [57–60]

GABA for supporting sleep quality* [61]

L-Cysteine in support of general immune health* [38,41,43,44,50,53,62]

Green tea extracts in support of general immune health* [39,40]

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.


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