At Thorne, we’ve noticed an uptick in interest in L-theanine the past year. Is it perhaps due to COVID stress?

This article focuses on how L-theanine can help you deal with stress, as well as having more restful sleep.* But first, what is L-theanine? It’s a non-protein amino acid – meaning it has the structure of an amino acid, but isn’t used as a building block to make proteins. It was discovered in Japan in 1948 as a constituent of green tea, and although it is found primarily in the tea plant (Camellia sinensis), it is present in several other plants, including mushrooms like Boletus badius (bay bolete). L-theanine is synthesized in the roots of plants, but it concentrates in the leaves.

Does all tea contain L-theanine?

Although green tea is its best-known source, L-theanine is found in nearly all teas – black, white, green, and oolong – to one extent or another. The two tables below illustrate the teas that contain the highest and lowest amounts according to a study that assessed the theanine and caffeine content of 36 commercial brands of tea.Another study showed that theanine offsets the stimulatory effect of caffeine – although the ratio of theanine to caffeine dictates to what extent.2 To see all 36 teas, as well as the caffeine and caffeine/theanine ratios, access the full text of the study here.

There are approximately two grams (or 1 tablespoon) of tea per cup. So, if you double the amounts per gram listed below, then that would approximate how much theanine you might get in a cup of tea – an average of 20-25 mg from a cup of tea from the highest-content list.

Teas with the highest L-theanine content1

Commercial tea tested

Type of tea

mg L-theanine per gram of tea leaves

Hwa Gung

oolong

12.37

Korean Green

green

10.93

ChinaYunnan FOP

green

10.88

Lord Nelson Earl Grey

black

10.85

Vietnamese Green

green

10.11

Tradition

oolong

9.78

Mao Feng White

white

9.11

Mao Feng Green

green

8.53

 

Teas with the lowest L-theanine content1

Commercial tea tested

Type of tea

mg L-theanine per gram of tea leaves

China Yunnan Pu-Erh

pu-erh

0.0

Darjeeling Happy Valley

black

2.09

Twinings Earl Grey

black

2.47

Earl Grey

black

2.70

Japanese Bancha

green

2.81

ChinaYunnan White

white

3.24

Russian Samovar

black

3.80

China Gunpowder

green

3.88

 

What does L-theanine do in the body?

Neurotransmitters: L-theanine can positively impact the key neurotransmitters (brain chemical messengers) involved with stress, sleep, mood, focus, and memory.* L-theanine enhances the production of the neurotransmitters dopamine and serotonin, and also appears to play a role in the formation of GABA – a neurotransmitter that acts like a "brake" during times of stress.* L-theanine helps establish balance in the neurotransmitter system, resulting in improvements in the mental/emotional and physical disturbances resulting from being overly stressed.*

Read more: Stress and Sleep and the benefits L-Theanine rich Tea

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