Theine – what is it? Properties, uses and effects

In the 19th century, a compound called theine was isolated from tea leaves. A dozen or so years later, it was established that theine and caffeine – which had previously been isolated from coffee – were in fact the same chemical substance. However, the term "theine" has remained in use and is still sometimes applied to the caffeine naturally present in tea. The natural source of theine is the leaves of Camellia sinensis, from which black, green, white, oolong and matcha teas, amongst others, are produced.

1. Characteristics of theine
2. Theine dosage
3. The effects of theine
4. Alertness and reduced drowsiness
5. FAQ

Characteristics of theine

Theine is simply caffeine found in tea. It is not a variant of caffeine, nor is it a different compound with a milder effect. The caffeine molecule derived from tea leaves has exactly the same chemical structure as the caffeine found in coffee beans, guarana or kola nuts. The term ‘theine’ is therefore used primarily for historical reasons, whilst in chemistry and nutritional science the term ‘caffeine’ is used. This compound belongs to the methylxanthines, a group of natural substances produced by a small number of plants.

In tea leaves, caffeine is found alongside many other components, including polyphenols and L-theanine. L-theanine should not be confused with theine; they are two completely different substances. Theine is caffeine and acts primarily on the central nervous system, whereas L-theanine is an amino acid that occurs naturally in tea.

After drinking tea, caffeine is absorbed from the digestive tract into the bloodstream, and can then enter the nervous system. The body does not distinguish whether a particular molecule came from an espresso, black tea or green tea. The differences felt after drinking different beverages may stem primarily from the amount of caffeine consumed, the serving size, the method of preparation and the presence of other ingredients.

Methylxanthines (including caffeine/theine) and their natural sources

Theine dosage

The European Food Safety Authority (EFSA) estimates that a 220 ml cup of black tea contains approximately 50 mg of caffeine (theine). By way of comparison, a 60 ml espresso contains on average around 80 mg, whilst 200 ml of filter coffee contains around 90 mg. These are approximate figures.

No specific recommended intake is set for theine. When assessing intake, the total amount of caffeine from all sources throughout the day is taken into account. According to the EFSA, a single dose of up to 200 mg of caffeine does not raise safety concerns in healthy adults, and a total intake of up to 400 mg per day, spread throughout the day, also does not pose a safety concern for the healthy adult population, with the exception of pregnant women. EFSA also points out that as little as 100 mg of caffeine consumed close to bedtime may affect the duration and quality of sleep in some adults.

The effects of theine

As theine is caffeine, its effects stem primarily from caffeine’s impact on the central nervous system. One of the main mechanisms is the blocking of adenosine receptors. Adenosine is a naturally occurring substance in the body, the signalling of which in the brain is associated, amongst other things, with a gradual reduction in nervous system activity during prolonged periods of wakefulness. A caffeine molecule can occupy the binding site in the adenosine receptor, but does not activate it. As a result, some of the signals associated with adenosine are temporarily attenuated.

Alertness and reduced drowsiness

The EFSA notes that caffeine stimulates the central nervous system and, in moderate amounts, increases alertness and reduces drowsiness. EFSA also gave a positive assessment of the relationship between caffeine intake and increased alertness in the adult population; however, the assessment of this effect considered products providing at least 75 mg of caffeine per serving. This does not, however, mean that a higher amount always produces a stronger or more beneficial effect, as the response to caffeine varies from person to person. The body’s response is influenced, amongst other things, by the amount consumed, the regularity of caffeine intake, the time of day and the individual rate at which it is metabolised (which depends on genes).

"Theine and caffeine are the same chemical substance. The differences in the perceived effects of tea and coffee stem mainly from the dose of caffeine, the method of preparation, and the presence of other components, such as polyphenols and L-theanine. Therefore, when assessing safety, what matters is the total amount of caffeine consumed throughout the day, regardless of its source.” Anna Zięba – Dietitian

FAQ

Are theine and caffeine the same thing?

Yes. Theine is the historical name for the caffeine found in tea. Chemically, it is exactly the same substance that is also found in coffee, guarana and yerba mate.

Is theine milder than the caffeine in coffee?

Not theine itself, as it is the same molecule. Differences in how it is perceived may stem from the lower dose of caffeine in a serving of tea, the slower rate at which the drink is consumed, and the presence of other compounds, such as L-theanine and polyphenols.

How much theine is there in a cup of tea?

According to the EFSA, a 220 ml cup of black tea provides an average of around 50 mg of caffeine. The actual amount depends on the type of tea, the quantity of leaves, the water temperature and the brewing time.

Does green tea contain theine?

Yes. Green tea also contains caffeine, or theine. The amount may be lower than or similar to that in black tea, depending on the raw material and method of preparation.

Is L-theanine the same as theine?

No. L-theanine is an amino acid found naturally in tea, whereas theine is simply caffeine. They are two different substances.

How does theine work?

Theine blocks adenosine receptors in the brain, which can increase alertness, reduce drowsiness and improve concentration in the short term.

How much theine can you consume per day?

As theine is caffeine, you should take into account the total amount of caffeine from all sources. The EFSA states that, in healthy adults, a total intake of up to 400 mg per day does not usually raise any safety concerns.

Sources: 

• Ribeiro, J. A., & Sebastião, A. M. (2010). Caffeine and adenosine. Journal of Alzheimer's disease : JAD, 20 Suppl 1, S3–S15. https://doi.org/10.3233/JAD-2010-1379
• Chin, J. M., Merves, M. L., Goldberger, B. A., Sampson-Cone, A., & Cone, E. J. (2008). Caffeine content of brewed teas. Journal of analytical toxicology, 32(8), 702–704. https://doi.org/10.1093/jat/32.8.702
• Wikoff, D., Welsh, B. T., Henderson, R., Brorby, G. P., Britt, J., Myers, E., Goldberger, J., Lieberman, H. R., O'Brien, C., Peck, J., Tenenbein, M., Weaver, C., Harvey, S., Urban, J., & Doepker, C. (2017). Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 109(Pt 1), 585–648. https://doi.org/10.1016/j.fct.2017.04.002