1. What is theanine?

theanine has a relaxing effect.  This chemical component was discovered by Yajiro Sakato, a Japanese scientist about 70 years ago.

Theanine gives you an umami taste and shade-grown teas such as gyokuro and matcha preserve more theanine than open-field grown teas like tamaryokucha and sencha.  Higher grade teas have more theanine than standard grade teas.

Another important fact is, theanine is created in tea tree roots.  Then it is carried from roots to stems, to veins, and eventually reaches leaves.  Stems have more than 2 times theanine than leaves.  Because they are closer to roots and sunshine breaks down theanine in leaves into other components to help create catechins.

Theanine is syntesized in root

2. How theanine works on the human brain?

When we are relaxed and calm, our brain releases more alpha waves.  This research shows theanine (L-theanine) intake leads to more alpha waves in human brains.  People reported clarity of mind, calm and relaxed when taking theanine.

Alpha Wave Topography

(Kobayashi et al. “Effects of L-Theanine on the Release of a-Brain Waves in Human Volunteers”, Nippon Nogei Kagaku Kaishi, Vol.72, No.2, 1998, P155, Link to this research paper)

3. Opposing effect of some tea components

However, when you drink Japanese teas, some of the chemical components work against each other.  Theanine works against caffeine and EGCG catechin.  This is why caffeine works milder in Japanese green teas.  Theanine suppresses the work of caffeine.

Opposing Effect of Tea Components

4. Brewing Recommendation – Cold Brew

Then how can we take more theanine and less caffeine and less EGCG catechin?
When we brew with hot water, caffeine is extracted well with hot water and theanine is not so sensitive to the water temperature.

Then how about cold water?  The research on sencha teas below indicates each component has different infusing speeds with cold brew (condition: keep in a refrigerator).

(Fukushiyama et al. “Effect of the Soaking Time of a Green Tea Bag in Cold Water on the Flavor and Amount of Constituent Extracted”, Journal of home economics of Japan, Vol.50, No.1, 1999, P66, Link to the research paper)

If you use cold water to brew, theanine is easily extracted while caffeine and catechins are slow to be in your tea liquid.  Cold-brew is one way to take more theanine and less caffeine and catechiins.