- Tea is a natural source of L‑theanine.
- Studies have observed its positive effects on attention, stress resistance and sleep quality.
- L‑theanine can also be taken in the form of dietary supplements.
What is L‑theanine?
L‑theanine is an amino acid naturally occurring in all types of tea. In recent years, the effects of L‑theanine have been studied mainly in relation to sleep, anti‑stress, and supporting brain function. How does L‑theanine work, what is the appropriate dosage and what should I look for in an L‑theanine dietary supplement?
L‑theanine as a natural component of tea leaves
L‑theanine was first isolated from the leaves of the Japanese Gyokuro tea in the 1950s. It was soon found to have a characteristic "caramel" taste on its own and contributes to the resulting umami taste of some teas. The formation of L‑theanine in the tea plant takes place in the roots, where the proportion of L‑theanine (on a dry weight basis) is approximately 6%. L‑theanine then enters the stems, leaves and terminal buds (tips). The amount of L‑theanine in the dried leaves is approximately 6mg per 1g of tea, so the average cup of tea generally contains no more than 10‑20mg of pure L‑theanine.
Among the teas with the highest L‑theanine content is Japanese Matcha powder tea, which is produced by grinding Gyokuro green tea. The proportion of L‑theanine is several times higher than that of other teas, which also contributes to the specific taste of Matcha tea.
Although in 2011, the European Food Safety Authority (EFSA) rejected an application for the use of health claims in relation to foods containing L‑theanine, studies in recent years show that the use of this substance can have a number of positive effects on the human body.
Characteristic taste and effect on brain function
The taste of pure L‑theanine is reported to be slightly 'caramel' with a hint of umami flavour. L‑theanine is also the only component of loose tea substances that contributes to the umami flavour in the resulting beverage (Japanese green teas such as Sencha or Gyokuro). Studies also show that it can suppress bitter taste notes like grapefruit or caffeine due to these properties.
Once absorbed, L‑theanine enters the bloodstream, where it can then pass through the blood‑brain barrier to the brain. Studies show that L‑theanine increases alpha‑brain wave activity, which is also how scientists explain its beneficial effects on stress and anxiety.
A separate topic is the simultaneous action of caffeine and L‑theanine. A number of studies have shown that the simultaneous use of caffeine and L‑theanine has a synergistic effect, i.e., the two substances support each other in their effects on attention and concentration. Some experts believe that the L‑theanine present in green or black tea is the reason why a cup of tea has a different effect on alertness and attention than an equivalent amount of caffeine from coffee or a caffeine tablet with synthetic caffeine.
Research confirms positive effects on memory, attention and work performance
The main effects of L‑theanine include its influence on the central nervous system, particularly on attention and work performance in terms of cognitive function. Although most of the available studies are based on animal experiments, the effects are also confirmed in human studies.
- In a 2015 study on 20 healthy men, researchers concluded that a dose of 200mg of L‑theanine per day improved attention and cognitive function similarly to caffeine. This study also described synergistic effects between the actions of caffeine and L‑theanine.
- In a Japanese study from 2021, the use of L‑theanine was tested on a total of 69 Japanese women and men. It was shown that after taking L‑theanine at a dose of 100mg,reactions were speeded up, and attentionwas improved. The study participants also made fewer errors in working memory tests.
- In a 2016 study of 36 young men and women, it was shown that taking L‑theanine at a dose of 200mg led to a reduction in cortisol levels. Taking L‑theanine has also been shown to have a positive anti‑stress effect.
- In an RCT study published in 2022, the effects of L‑theanine were investigated in 27 adult subjects at doses of 100, 200 and 400mg of L‑theanine per day. At higher doses, increased attention and improved working memory were observed.
Studies also show that taking L‑theanine attenuates the acute increase in blood pressure induced by caffeine. A similar effect was also observed in stressful situations, where the use of L‑theanine led to an acute reduction in blood pressure.
How to take L‑theanine for maximum effectiveness?
L‑Theanine occurs naturally in tea of all types but is most abundant in yellow and green tea. Depending on the specific species, the average content in 1 cup is approximately 10‑20mg of L‑theanine. Most of the studies confirming the positive effects of L‑theanine on the human body work with doses of 100‑200mg of L‑theanine per dose, an order of magnitude higher than that contained in 1 cup of tea. So, although tea naturally contains L‑theanine, the question is to what extent the above effects can be applied to a single cup of tea.
L‑theanine can be taken in the form of dietary supplements. Currently, the use of L‑theanine originating from green tea extracts is permitted in the European Union and can be standardised up to 40% L‑theanine. In contrast, a synthetic form with 98% L‑theanine, obtained by synthesis from glutamic acid and ethylamine, is not yet authorised in the EU.
The appropriate dose seems to be in the range of 100‑200mg of L‑theanine per dose. A combination with caffeine is also popular, with an expected synergistic (mutually supportive) effect that leads to a boost in concentration and attention.
L‑Theanine 250mg
Bottom line
L‑theanine is an amino acid naturally occurring in tea. There are approximately 10‑20mg of L‑theanine in 1 cup of green tea, with green and yellow tea containing more than oolong or black tea. Studies in recent years suggest that taking L‑theanine has a positive effect on concentration, attention and may reduce stress. Some research also suggests that it has relaxing effects, promotes sleep quality, and reduces the time it takes to fall asleep.
In dietary supplements, L‑theanine can be taken in the form of green tea extract, which is standardized for L‑theanine content. It acts synergistically with caffeine and 100‑200mg per dose is recommended as an appropriate dose depending on weight.
