"Increasing immune strength" by drinking green tea

Preventing virus infections

It is said that green tea contains components that directly works to disable virus infections, such as influenza virus and the common cold virus. Tea catechin is one of the typical components. Influenza virus contagion starts when the 2 types of protein which extends out in spiked shapes from the surface of the virus cells, infects the cells of the throat and nasal passages. 

Tea catechin works directly against the spiked shaped proteins and suppresses its effects, thereby prevents the infection of the influenza virus. It has become clear that the Epigallocatechin Gallate (EGCG) has the strongest effect.

In addition to the tea catechin, it is said that Strictinin which is found 0.5% in dried tea leaves, also prevents virus infections that are the cause of influenza and childrens' common cold infections. The function of Strictinin differs from that of the tea catechin and is said to prevent virus infections by interfering with the binding of the virus membrane and the cell membrane.

SUZUKI Takashi (Professor, School of Pharmaceutical Sciences, University of Shizuoka)

Preventive measures for the influenza 

Influenza is an acute and severe upper respiratory tract infection that is prevalent in winter across the world. The infection is caused by the influenza virus which is spread through airborne droplets and contact with the virus. It is highly contagious and can cause pneumonia and brain fever. 

Protective measures become highly important. These include vaccination, washing hands, use of masks and gargling, but none of these will guarantee that you will not catch the influenza virus. In addition to these measures, it has been recently said that gargling with tea catechin, and drinking green tea can help prevent infection.  

Protective measures by gargling with tea catechin

Tea catechin combines with the spikes on the surface of the influenza virus, in order to obstruct the absorption of the virus to the surface of the host cell. Thereby, preventing infection.  It is said that the effects do not change according to the type of influenza.  

In order to study the effectiveness of tea catechin gargling for the prevention of influenza, a clinical research was conducted on a group of people admitted in a special nursing home for the aged.  The group gargled with extracts of green tea catechin (total catechin concentration 200μg/mL, equivalent to half the concentration of plastic bottled green tea on the market) 3 times a day for 3 months. Compared to gargling with water, there was a decrease in the number of influenza infections.  

Protective measures by drinking green tea

In addition to catechin, green tea also contains components such as theanine and vitamin C which increases the immune strength against these infections.  Drinking green tea is also anticipated to prevent influenza infection.

 In fact, in Kikugawa City (Next to Kekegawa City where Kimikura lives) a green tea producing region in Shizuoka, an epidemiological survey was conducted amongst elementary school students. Students who consumed 1 to 5 cups of tea a day had a lower chance of being infected with influenza, compared to those who consumed less than a 1 cup of tea a day.  

YAMADA Hiroshi (Professor, School of Pharmaceutical Sciences, University of Shizuoka)


Increasing immune strength

In winter, we all start to be concerned about the common cold or influenza. Our body balances the activity and suppression of the immune system, in order to prevent various pathogens from entering the body.  Unfortunately our immune strength deteriorates due to various reasons, and when our barrier against pathogens weaken, we become prone to infections.  

Epigallocatechin(EGC) which improves the mucosal immune system

Mucous membranes of the respiratory system and digestive system which come in contact to the outside world, are the main infection routes of pathogens. The mucosal immune system prevents pathogens from entering our body through the mucous membrane and is at the frontline of biological defense. EGC which is a type of catechin, is known to improve the function of the mucosal immune system.  

However, the ratio of EGC and EGCG contained varies according to the water temperature when brewing the tea. The effects of EGC are weakened by Epigallocatechin gallate (EGCG).  EGCG is easily extracted when brewing green tea with boiling water, thereby weakening the effects of EGC.  

Brewing green tea with cold water decreases the amount of EGCG extract,  thereby maximizing the effects of EGC. We recommend brewing green tea with cold water, in order to activate the mucosal immune system and prevent the intrusion of pathogens.  



MONOBE Manami (Institute of Fruit Tree and Tea Science, NARO)

Related links:
How to brew with cold water 

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