Boosting Immunity with Japanese Green Tea

Strengthening immunity has been of serious concern ever since the pandemic started. Several of our customers have also inquired about tea that can help fortify their or their family's immunity.

Japanese green tea is known to be a powerful immunity booster. There are essential tips in preparing tea to maximize its effectiveness.

In this article, we'll jump into the details of Japanese green tea and how it helps immunity.

This article was last modified December 11th, 2022. by Yuki

The Green Tea Catechin EGC that Strengthens Our Immune System

Green Tea Catechins are nutrients found in green tea that contain several important health benefits for humans.

EGC, one of the critical Catechins found in Japanese green tea, plays a crucial role in boosting the effectiveness of our body's immune system.

First, let's talk briefly about how our immune system works.

Our immune system fights off sickness by making antibodies. An antibody called IgA is one of the key antibodies that the body produces to do so.

EGC improves the amount of IgA in the body.

This happens as EGC improves the functions of macrophage and dendritic cells, which are vital functions in our immune system, by removing microorganisms and dead cells in the intestinal tract.

It allows for more IgA to be produced efficiently without obstruction.

The interesting thing is that while the EGC helps immunity, another key tea catechin found in green tea called the EGCG has an effect of canceling the immunity effects of EGC.

EGCG is also a powerful compound with incredible health benefits in its own right. However, when it comes to immunity, the EGCG works negatively.

Since all Japanese green tea have both EGC and EGCG, achieving a high EGC: EGCG ratio is important to strengthen your immunity.

We can easily achieve this with a simple trick; cold-brewing green tea. [1]

Cold Brewing Tea to Increase Immunity

Although EGCG and EGC are green tea catechins, they dissolve in water at different temperatures.

EGC can be extracted at room temperature, while EGCG requires more than 80 degrees Celsius water to be effectively extracted into the tea.

Studies show that the continued consumption of cold brew Japanese green tea of 2 cups a day increases the levels of IgA, which protects against the invasion of diseases. [1]

By cold-brewing your Japanese tea, you can achieve a high EGC ratio, which will help strengthen your immunity.

Type of Tea to Maximize Green Tea Catechin

When looking for tea types with the highest amount of green tea catechin, it's best to go with the most standard Japanese green tea. These are the Sencha and the Tamaryokucha.

The Sencha is the most standard type of Japanese Green tea. It is an "unoxidized tea," where the loose leaf maintains its natural green colors. It is also cultivated and manufactured in the most standard way.

Other types of Japanese green tea can be considered alterations of the Sencha, intended to enhance the taste of the tea. Here are some examples below.

  • A Gyokuro or Matcha shades the leaves from the sun to reduce the amount of Catechins. This leads to a delicious tea. However, it reduces the number of catechins in the leaves.
  • A Genmaicha is a flavored green tea with roasted brown rice kernels. While the tea leaf contains similar amounts of catechin to a Sencha, the additional brown rice dilutes the amount of Catechins in the tea.
  • A Houjicha is Sencha roasted after the initial process to give a light and heartwarming taste. The roasting significantly reduces the number of catechins, hence not suitable for enhancing immunity.

Sencha is the most basic form of Japanese green tea and contains the most amount of green tea catechins. Therefore we recommend you stick with Sencha.

While relatively rare, the Tamaryokucha is a basic form of Japanese green tea with similar levels of tea catechin. If you can find Tamaryokucha near you, it's certainly an option to help take green tea catechins.

Choosing Cultivars with High EGC/EGCG Ratio

Different cultivars have different levels of EGC and EGCG. So if you want to be extremely picky and have the luxury of available choices, you can also check the different types of cultivars that make green tea.

Regarding a high EGC/EGCG ratio, the "Yutakamidori" cultivar comes out extremely high with a 0.69. Saemidori follows this with 0.66, and Kanayamidori with 0.61.
The most common Yabukita cultivar is 0.55, which is practical as well. So if you don't have a choice, you can go with the most common cultivar in the Japanese green tea market. [3]

Author Yuki


Yuki is the Editor-in-Chief AND Community Manager at Tealife. He bleeds Japanese Tea and loves being a part of the Japanese Tea journey of others. Writes, does events, conducts tasting sessions, drinks, drinks and drinks tea! Easily accessible - hit him up on whatsapp (+65) 85882980.


[1] Monobe M. et al. Effect of Cold Extract of Green Tea
(Camellia sinensis L.) on Salivary
Secretory IgA Levels in Habitual Green
Tea Drinker: A Preliminary Study. 茶業研究報告, 2012 113: 71-76 dio:

[2] Monobe M. et al., 緑茶冷水(4℃)浸出液のカテキン浸出特性及び茶期・品種の異なる緑茶冷水浸出液がマクロファージ様細胞の貪食能へ与える影響, 茶業研究報告, 2012, 2012 巻, 114 号, p. 114_29-114_36, 公開日 2015/10/30, Online ISSN 1883-941X, Print ISSN 0366-6190,

[3] 物部 真奈美, 池田 麻衣, 江間 かおり, 徳田 佳子, 山本(前田) 万里, 緑茶冷水(4℃)浸出液のカテキン浸出特性及び茶期・品種の異なる緑茶冷水浸出液がマクロファージ様細胞の貪食能へ与える影響, 茶業研究報告, 2012, 2012 巻, 114 号, p. 114_29-114_36