L-Theanine | L-γ-Glutamylethylamide | 5-N-Ethyl-Glutamine
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. 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 doses, 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., the best responses occur when it’s dosed within a range as opposed to more being better). That said, the dose 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 synergistic ingredient combinations. In some cases, ingredients tend to be most complimentary 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, L-theanine might be dosed to provide about double the dose of caffeine and/or theobromine (i.e., ~2:1 ratio). But when used in combination with GABA before bedtime for supporting sleep, it might be dosed at as little as 20% of the GABA dose (i.e., 1:5 ratio). Following an oral dose, the amount of L-theanine in the brain increase within the first hour (i.e., it’s able to cross the blood-brain barrier, so in general, L-Theanine has fairly quick onset and is often experienced within 30-45 minutes of taking it.
Supports executive function[4,9]
Supports faster reaction times
Supports alpha (α) brain waves (α-waves are associated with relaxation, selective attention, and mental alertness)[1,3,10–13]
Supports hippocampal activity
Supports dopamine signaling[15–21]
Supports serotonin signaling
Supports GABA levels in the brain
Binds to glutamate receptors (with low affinity)[22–24]
Supports hippocampal neurogenesis 
Supports brain-derived neurotrophic factor (BDNF)[6,24,25]
Supports neuroprotective functions[7,8,26–28]
Mood and stress
Supports a calm/relaxed mood[4,8,9,13,14,29–32]
Supports a positive mental-emotional bias[4,9]
Modulates psychological and physiological stress responses
Supports healthy behavioral and cognitive responses to stress[26,34]
Reduces fight or flight nervous system activity (i.e., promotes relaxation response)
Supports sleep efficiency and quality[4,9,35,36]
Counters some of caffeine’s effects on deep sleep
Supports innate immunity[38–40]
Supports adaptive immunity[38,40,41]
Supports gamma delta T cell function[42,43]
Modulates immune signaling[38,44]
Supports gut microbiota
Supports amino acid absorption
Healthy aging and longevity
Pro-longevity (Caenorhabditis elegans)
Caffeine in cognitive performance[48–51]
GABA for supporting sleep quality
L-Cysteine in support of general immune health[53–59]
Green tea extracts in support of general immune health[60,61]
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