Integrative Health Zone
Educate You!

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.¹ 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

Teas with the lowest L-theanine content¹

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.*