Want to relax? Drink green tea

It is well known that drinking green tea is accompanied by a feeling of relaxation. This effect is attributed to L-theanine, a unique amino acid found only in tea plants. L-theanine was discovered in tea leaves as early as 1949 and makes up only 1-2% of the dry weight of tea leaves. It exists only in free form (not as part of proteins) and is the main amino acid in tea, accounting for up to about 50% of the total free amino acids. Chemically, it is g-ethylamino-L-glutamic acid.

Theanine acts as an antagonist to caffeine-induced paralysis. It is rapidly absorbed in the intestines and exhibits characteristic physiological effects. Among green tea varieties, Japanese Gyokuro leaves contain large amounts of l-theanine because the tea leaves are shaded from direct sunlight before harvesting.

Relaxing effect

In general, weak electrical pulses called brain waves are constantly generated on the surface of the brains of animals and humans. There are four types of brain waves according to their frequency: α, ß, δ, and θ waves. Each type of brain wave corresponds to a specific mental state, namely:

- δ waves – deep sleep – frequency 0.5-3Hz

- θ waves – light sleep – frequency 4-7Hz

- α waves – wakefulness, relaxation – frequency 8-13Hz

- ß waves – wakefulness and irritation – frequency 14Hz

The creation of alpha waves is considered an indicator of relaxation. Experiments have shown that alpha waves increase 40 minutes after consuming L-theanine.

Alpha waves are typical for the brain in an inactive state, and most people are in this state when they are awake with their eyes closed. Alpha waves are the main indicator of conscious attention and represent the gateway between consciousness and unconsciousness.  L-theanine stimulates alpha brain waves, which are associated with relaxation, but at the same time keep a person awake. It helps to relax the mind and speeds up a person's reactions.

While other active ingredients in tea, catechins, taste bitter, L-theanine is sweet. Together, these two ingredients create a perfectly balanced tea flavor. Repeated experiments have shown that L-theanine has positive effects on the mind and improves memory. Experiments have shown that alpha waves increase 40 minutes after consuming L-theanine. People can take advantage of the fact that even when they decide to relax, their brains function just as efficiently as if they were working. It is recommended to drink a cup of green tea 40 minutes before starting work or studying.

Although green tea contains caffeine, it does not cause nervousness thanks to L-theanine. Thanks to its L-theanine content, it has a calming effect. L-theanine mitigates the effect of caffeine, which causes irritability or nervousness, and calms the mind.

Lowering blood pressure

Blood pressure regulation depends on catecholaminergic and serotonergic neurons in the brain and peripheral nervous systems. Theanine has been found to lower serotonin levels in rats. The effect is likely dose-dependent. A significant reduction was observed when high doses of theanine were administered. Glutamine, which is chemically similar to theanine, did not show any effect on lowering blood pressure. Theanine has a calming effect on the mental state, probably by lowering blood pressure.

Improved learning ability

Animal experiments have shown that theanine may affect the metabolism or release of certain neurotransmitters in the brain. In particular, dopamine and serotonin, which are closely related to memory and learning ability. The release of dopamine significantly affects human emotions. It is known that there are independent transport systems for circulating neutral, basic, and acidic amino acids. It is believed that theanine is absorbed in the intestines and selectively incorporated into the brain via the L-system (a transport system for large neutral amino acids, e.g., leucine, isoleucine, valine, etc.). Theanine is excreted within 24 hours. Experimental results suggest that theanine administration may reduce serotonin synthesis and increase degradation, or inhibit serotonin release.

Source: Trends in Food Science & Technology, 10, 1999, No. 6 7, p. 199 204