"Coffee or tea?" "It's the same for me, you choose".

How many times you heard about caffeine? And how many about theine? Some people say they prefer drinking tea because coffee makes them to energetic and makes them experience increased heart rate or sleep disturbance. However, as it will be explained in this article, these two molecules are really... the same! The only difference is the name and it depends on when the caffeine is found (either in the coffee or in the tea).

Caffeine and theine: two names, same molecule

As we just said, caffeine and theine are two different names used for the same molecule. They do not have any difference in terms of molecular structure, but the different name derives from the different source from which they are assumed. If drinking coffee, the molecule takes name of caffeine, while if this is absorbed by our body through tea, this molecule is called theine. The effects of this molecule in our body might look different depending on whether we drink tea or coffee, but this is just an illusion: indeed, usually a cup of tea contains more water than a cup of coffee, so the difference in the effects originated by assuming this substance resides in how much diluted the caffeine (theine) is. However, as it will be explained later in this article, other differences observed in the effects produced by tea and coffee can be related to other additional substances present in the tea leaves, which are not present in the coffee beans.

How does caffeine work?

Caffeine is the world's most popular stimulant and psychoactive substance. The most popular dietary sources of caffeine are coffee, tea, chocolates, and soft drinks. However, different varieties of coffee plants and also different parts within the same species show different levels of caffein content. Caffeine can also be consumed through medications used to treat headaches, colds, and allergies, in which caffeine acts as a potentiator of the analgesic effects of these drugs. Caffeine is also used cosmetically in cellulite-reducing treatments and, thanks to its ergogenic properties, it is also widely utilized as a performance-enhancing supplement by athletes.

Chemically speaking, caffeine is an heterocyclic methylxanthine derivative with a purine base, which makes it very versatile and able to work via different mechanisms of actions in or body. Indeed, caffeine can act as an antagonist of adenosine receptors, inhibitor of phosphodiesterase enzyme, it can promote the calcium release from intercellular stores, and it acts as an antagonist of GABA type A receptors. The adenosine receptors inhibition represent the most common and known effect of caffein in our body and this will be explained to follow as an example of the many effects of this psychostimulant in our body.

Adenosine receptor are usually stimulated by adenosine, which upon its binding, can alter cellular concentrations of cyclic adenosine monophosphate (cAMP). These alterations, that are different depending on which adenosine receptor type is stimulated, can decrease or increase the cAMP levels, having as a result the triggering of several metabolic, cardiovascular, and neuronal responses.

Caffeine structure is very similar to that of the adenosine. Therefore, caffeine can non-selectively bind to the adenosine receptors and competitively inhibit them, acting as an adenosine antagonist. For instance, binding of adenosine to the receptors in the central nervous systems will promote drowsiness, while binding of the caffeine will result in temporary relief of drowsiness, giving us the feeling of being more energetic upon drinking coffee.

Does theine work in a similar way?

As said earlier, theine is contained in tea leaves, but the effects of theine are perceived as different, due to the presence of additional substances. Tannins contained in tea leaves control the effect of theine. Indeed, theine is released into the bloodstream uniformly over a long period of time, lasting between 6 to 8 hours. Instead, caffeine present in coffee, is released quickly producing a peak of intensity that falls after a period of 2 to 3 hours.

Another type of tannins called thearubigins, tends to reduce the effect of theine on the body. When tea is brewed, theine is released first, before the tannins: then, in the first moments of the infusion, the tea will be the strongest. The thearubigins released afterwards counteract this effect and reduce the action of theine on the brain. This is why, in order to obtain the most of the stimulating effects of a cup of tea, tea should be steeped for less than two minutes!

Theanine, an amino acid present in tea, has a relaxing effect counterbalancing the effects of theine. Tea leaves also contain many vitamins (C, A, B1, B2, B6, B9, E, K), which have beneficial effects on the whole body. In particular, theanine (L-theanine, more correctly) has been historically reported as a relaxing agent, which increases brain serotonin, dopamine, GABA levels, with a moderate affinity for AMPA, kainate and NMDA receptors. Because of its structural similarity with L-glutamine, it has been shown to exert neuroprotective effects in animal models possibly through its antagonistic effects glutamate receptors, causing an improvement in learning and memory.

Other effects for drinking tea have been described, but many of them are still under investigation and they have not been confirmed yet because of lack of information in literature and lack of studies focussing on this topic.

Conclusion

As we showed in this article, both drinking coffee and tea can have beneficial effects (with moderation). Independently on the personal taste, the preference of one drink over another might depend of the benefit we want to take advantage of (fast wake up or slow energy-building). However, always have in mind you are drinking the same molecule and the effects can be very similar even if the perception of them is that they look different. Hopefully, in the future we will know more about caffeine and its effects on human body and we will discover more about the natural power of coffee and tea as beverages!

References

Vundrala Sumedha Reddy, S. Shiva, Srinidhi Manikantan, Seeram Ramakrishna, Pharmacology of caffeine and its effects on the human body, European Journal of Medicinal Chemistry Reports, Volume 10, 2024, 100138, ISSN 2772-4174, https://doi.org/10.1016/j.ejmcr.2024.100138,(https://www.sciencedirect.com/science/article/pii/S2772417424000104)

Nathan PJ, Lu K, Gray M, Oliver C. The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother. 2006;6(2):21-30. PMID: 17182482.

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