Although the relaxing properties of tea have been speculated for some time, scientific evidence was lacking. Several recent human studies have shown that drinking tea four times a day for six weeks, enables people to recover faster from stressful events. This is due to a decrease in the hormone cortisol, which causes stress. Scientists speculate that ingredients in tea may affect neurotransmitters in the brain.
Theanine is a compound found almost exclusively in the tea plant, Camellia sinesis. Also found in one species of mushrooms and two other Camellia genus species, theanine is an amino acid being studied for its calming properties. Theanine comprises 50% of the amino acids in tea, and one to two percent of the dry weight of tea leaves.
In studies with rats, theanine was able to cross the blood barrier of the brain, increasing alpha-brain wave activity. This brain activity is a sign of induced relaxation. Of the four brain waves, Gamma, Theta, Alpha and Beta, Alpha waves create a relaxed physical and mental condition while the brain is awake and alert. Gamma and Theta waves are present during sleep, and Beta waves signify an awake and excited state.
Theanine is also known to improve concentration and ability to learn, support the immune system and lower cholesterol. A small study with Japanese university students showed that a relaxed and alert state of mind began about 40 minutes after the students took a 200mg theanine supplement.
More studies are being conducted to help understand the effect of theanine in tea.
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