Theanine for Stress

Since theanine is a structural analog to glutamate (glutamic acid), it can bind to the same receptors though at a lower affinity.  Glutamate is the most abundant neurotransmitter in your nervous system.  It is responsible for activating your neurons and is released in response to nerve impulses.  Downstream cellular functions from glutamate receptors are important for memory, learning, and neural communication and regulation. When theanine binds to glutamate receptors, it likewise can increase the activity of neurons to a small degree.  It can increase the production of other neurotransmitters, including dopamine, serotonin, and GABA.² 

People who habitually drink tea will be familiar with its calming effects.  These may stem in part from its theanine content, which has been found to help reduce anxiety.  Its interactions with specific glutamate receptors in the brain’s hippocampus have mild antipsychotic-like and antidepressant-like effects.³  Theanine can reduce both your perceived and physiological stress when performing tasks, and can even lower blood pressure.  It can also improve your sleep and your mood upon waking.⁴

Some studies suggest that theanine may be beneficial in other areas of neurological health in addition to its relaxation effects.  Animal studies and small clinical trials have noted improved learning abilities and memory from theanine supplementation.  It can also increase attention.  Taking theanine in combination with caffeine may improve attention and cognitive performance even greater than caffeine or theanine alone, but the research is inconclusive so far.^5,6  Theanine also has neuroprotective properties, possibly preventing neural degradation and helping to keep your brain and nerves functioning better as you age.^1-3  It can protect against neuron death following ischemia in the brain (stroke) and can improve mild cognitive dysfunction in elders.¹

The main source of theanine in the typical human diet is in tea.  Tea leaves, used to make black, green, and white teas, are very rich in theanine, with theanine comprising up to 50% of the amino acid content.  Growing tea partially in the shade, as is done to produce gyokuro or matcha teas in Japan, increases the tea’s theanine content.  Brewed black tea has a higher theanine content than green tea, with approximately 24mg and 8mg in the average cup of each, respectively.⁴

Since a minimum dose of 100-200mg theanine is needed for short-term effects, theanine supplements are now available with doses of the substance in this range.  Green tea extract supplements are also on the market, which contain high concentrations of theanine.