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.*

Because serotonin converts to melatonin in the pineal gland in your brain, improving serotonin levels ultimately results in improved melatonin levels, which in turn supports restful sleep.* In one study, 30 healthy adults were given either 200 mg L-theanine or a placebo daily for four weeks. The participants taking theanine took less time to fall asleep, had fewer sleep disturbances, and took fewer sleep medications, compared to the placebo group.3* Those taking L-theanine also had improved mental clarity, measured by verbal fluency, which isn’t hard to imagine – who doesn’t think better after a good night’s sleep?

Brain waves: L-theanine enhances brain alpha-wave activity, a marker of relaxation.* This effect has been observed to be most pronounced in individuals subjectively feeling the highest levels of stress.* 

In one study, healthy participants were given 50 mg L-theanine or a placebo, and brain waves were measured after taking the supplement and 45, 60, 90, and 105 minutes later.Alpha-wave production was significantly higher in the L-theanine group compared to the placebo group. 

Another study of Japanese university students found that 200 mg of L-theanine led to increased brain alpha-waves and a subjective sense of relaxation, along with decreased stress-related beta-waves.*In the same study, L-theanine administration also caused a dose-dependent relaxed, yet alert, state of mind without sedation, beginning approximately 40 minutes after ingestion.* In this study, L-theanine was compared with water and GABA (as PharmaGABA®). Both L-theanine and PharmaGABA significantly increased alpha-wave production compared to water, although alpha-waves were increased more when the subjects took GABA than when they took L-theanine.

In an animal study using brain wave analysis to evaluate sleep, a combination of L-theanine and GABA worked better than either alone in terms of time it took to fall asleep and sleep duration.6*

In general, L-theanine should be considered, along with exercise, a good sleep routine, and stress reduction practices to cope with stress and support restful sleep.*

Check out our new sleep support product – Sleep +. This product packs 200 mg of L-theanine, 100 mg of chamomile, and 1 mg of melatonin into each blueberry-flavored disc. 

Are you interested in knowing your stress or sleep hormone levels? Consider these easy at-home Stress or Sleep tests.


References

  1. Boros K, Jedlinszki N, Csupor D. Theanine and caffeine content of infusions prepared from commercial tea samples. Pharmacogn Mag 2016;12(45):75-79.
  2. Kakuda T, Nozawa A, Unno T, et al. Inhibiting effects of theanine on caffeine stimulation evaluated by EEG in the rat. Biosci Biotechnol Biochem 2000;64:287-293.
  3. Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients 2019;11(10):2362. 
  4. Nobre A, Rao A, Owen G. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr 2008;17 Suppl 1:167-168. 
  5. Abdou A, Higashiguchi S, Horie K, et al. Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans. Biofactors 2006;26(3):201-208. 
  6. Kim S, Jo K, Hong K, et al. GABA and L-theanine mixture decreases sleep latency and improves NREM sleep. Pharm Biol 2019;57(1):65-73.