There’s been a resurgence of interest in the anxiety-relieving powers of L-theanine, an amino acid found in green tea.1
Discoveries over the past two years have uncovered exciting additional properties of this nutrient best known for inducing calming, tranquilizing effects while simultaneously improving alertness.L-theanine
In this Research Update, we examine how L-theanine acts in the brain,
and review compelling new studies on its actions that include
potentially reduced risk of stroke and less brain damage if an ischemic
stroke were to occur.
L-theanine relieves anxiety in large part
because it bears a close resemblance to the brain-signaling chemical
glutamate. L-theanine produces the opposite effect in the brain.
While glutamate is the brain’s most important excitatory neurotransmitter, L-theanine binds to the same brain cell receptors and blocks them to glutamate’s effects. This action produces inhibitory effects.1,2 That inhibition to brain overactivity has a calming, relaxing effect in which anxiety fades.3
In addition to blocking excitatory stimuli at glutamate receptors in the brain, L-theanine also stimulates production of the inhibitory, relaxing neurotransmitter GABA, adding to its calming, anti-anxiety effects.2
Unlike prescription anti-anxiety drugs, however, some of which mimic GABA’s effects, L-theanine produces its anti-anxiety effects without producing sleepiness or impairing motor behavior.4 In fact, L-theanine has been shown in human studies to moderately improve alertness and attention while exerting its anxiety-reducing effects.5
Of particular interest are studies showing that L-theanine supplementation prevents the abrupt rise in blood pressure that some people experience under stress.1 The reason this is so critical is that many people have normal blood pressure readings at rest that spike up to dangerously high levels when subjected to stressful situations.
These periods of surging blood pressure inflict massive arterial
damage and are the main reason why at-home and at-office blood pressure
testing are so important.
Scientists are now increasingly interested
in applications for L-theanine far beyond its anti-anxiety properties.
Excessive glutamate stimulation of brain cells (excitotoxicity) is a
factor in development of long-term neurodegenerative disorders, stroke,
and schizophrenia.6,7 Therefore, L-theanine’s glutamate-blocking
capabilities make it promising for neuroprotection and prevention in
these areas.
And while its deeper mechanisms are still under investigation, there is tantalizing evidence that L-theanine influences expression of genes in brain areas responsible for fear and aggression (amygdala) and memory (hippocampus), helping to balance the behavioral responses to stress, and potentially improve conditions such as mood disorders, post-traumatic stress disorder (PTSD), and substance dependence.8
