Theanine is a non-protein amino acid and is similar in structure to glutamate, the most important excitatory neurotransmitter in the brain, which allows the compound to interact with glutamate receptors such as AMPA, kainate, and NMDA (at the glycine site). Which provides neuroprotection against glutamate toxicity. It’s mainly found in tea in small concentrations. Black tea contains approx 24g of theanine per cup and green tea only 8mg per cup. L-theanine is thought to cross the blood-brain barrier to exert its effects directly on the brain within 30 minutes and remains in the plasma and brain for a few hours. A more recent study has since confirmed that L-theanine is most effective in individuals who generally have high levels of anxiety (1).
Theanine is mainly used to enhance cognitive function, reduce anxiety and improve sleep quality.
Enhance cognitive function
Theanine has been shown to increase dopamine concentrations in the rat brain in a dose-dependent manner (2).
A dose of L-theanine (200mg) increases power in the alpha frequency band (8-13Hz) in the brain, parietal and occipital sites, after approximately 40min according to electroencephalogram (EEG) (3). This increase in alpha frequency band indicates that it relaxes the mind without inducing drowsiness and alpha activity is known to play an important role in critical aspects of attention (4).
Long term l-theanine administration also increases BDNF levels. BDNF helps to support the survival of existing neurons, and encourage the growth and differentiation of new neurons and synapses. Low BDNF is also found in people with depression.
Furthermore, theanine synergizes with caffeine, and the two together are better at improving cognitive function than each one alone. Caffeine with theanine increases speed on tasks, improves semantic memory, increases alertness, improves accuracy, attention, as well as memory formation and recall. More on coffee here…
L-theanine reduces the sympathetic nervous system response to acute stress and reduces heart rate, cortisol and salivary immunoglobulin A (s-IgA) (5). This will help you stay calm in a stressful situation.
Theanine reduces anxiety by inhibiting glutamate reuptake (6), via reduction of its transporter. Theanine stabilizes the glutamatergic concentration in the brain (7), and protects against the excitotoxic effect of glutamic acid (excitatory neurotransmitter).
Theanine very effectively increases brain GABA, striatum dopamine and glycine concentrations, while lowering serotonin levels globally, with region-specific increases in the striatum, hippocampus and hypothalamus (8).
It’s also an NMDA receptor agonist and it lowers cortisol. The NMDA receptor channels play an important role in synaptic plasticity and synapse formation underlying memory, learning and formation of neural networks during development in the central nervous system (CNS).
This all contributes to reduced anxiety without causing drowsiness (glutamate stabilization, increase GABA, lowers cortisol), increased focus (increase dopamine, NMDA agonist) and greater cognitive abilities. To enhance the cognitive enhancing effects, couple it with caffeine.