Caffeine in Tea

Contained in around 60 plants, caffeine is an alkaloid (1,3,7-trimethylxanthine) from the methylxanthine substance group. It is sometimes referred to as theine in tea, although this term is considered obsolete among experts. 

Caffeine tastes bitter and has a strong stimulating effect, which is why it has been used in Asia for thousands of years by Buddhist monks for meditation. It belongs to the secondary plant substances and is primarily formed by the plant to defend against insects (insecticide), microorganisms and other plants.

In green tea, caffeine is bound in a particular form and has a strong interaction with L-theanine. According to numerous studies, it has a stimulating effect and many major health benefits, which are unfortunately not well known. However, it can also trigger adverse side effects in caffeine-sensitive people and children, as well as during pregnancy and lactation.

Here we will explore the complex topic of caffeine, broken down into the following subsections:

Caffeine Comparison of Tea Varieties (in mg)

The comparison of the amount of pure caffeine between coffee, green tea, black tea and other caffeinated beverages is often not precise. Firstly, as mentioned above, it is decisive whether the caffeine is bound to special polyphenols (especially catechins) and which other ingredients (especially amino acids) are present. Secondly, the caffeine content is very different depending on the type of tea (ranging from 0.1% to about 6.2%).

Ultimately it is not about the caffeine content in the dry matter, but how much coffee or tea is used for brewing a cup and how much is dissolved in the water during brewing, depending on the water temperature and time. As an exception, the consumption of powdered teas (especially Matcha) should be mentioned, since here the whole leaf and caffeine is consumed. A comprehensive comparison can be found in the >>caffeine content table in mg<<.

Caffeine in Green Tea According to Variety

It should be highlighted that different green tea varieties have very different caffeine contents. This ranges from strong teas with a relatively high quantity of caffeine such as Gyokuro, Tencha, Matcha, Sencha first picking (about 2.3-3.5%, comparable to coffee); the average caffeine content of the variety Benifuuki and Sencha on the second picking (about 2.2%); the relatively low caffeine content of Genmaicha (Sencha mixed with rice) and tea from the coarser/older leaves (Bancha) (both about 1.5-2%); the very low caffeinated tea from the plant stems, Karigane from Sencha/Kukicha (about 0.5-1.5%); to the almost caffeine-free Sannenbancha (0.1-0.5%). Karigane from Gyokuro, however, contain a little more caffeine than Karigane from Sencha (about 1.7%). The different caffeine content of these varieties is mainly determined by three factors:

1. Young plant parts (buds and young small leaves) have significantly more caffeine than older plant parts (older leaves and stems).
2. The first picking/harvest has significantly more caffeine than the second.
3. Shaded teas (e.g. Gyokuro, Tencha, Matcha) have more caffeine than unshaded teas (Sencha, Bancha, Karigane, Kukicha, Benifuuki).

Additionally, it should be noted that a long storage period and especially fermentation reduces the caffeine content, as is the case with the Sannenbancha.

Useful Green Tea Combinations with Low Caffeine

Taking into account numerous aspects – such as the content of amino acids (especially L-theanine), catechins, tannins and the general health potency – there are three appropriate combinations of mild green teas, which differ in caffeine content. These range from 1. mild (for caffeine-sensitive people), 2. low-caffeine (for pregnancy, lactation and children) and 3. low-caffeine (for intolerance) varieties:

* Preparation: 2 tsp, 0.3 l water, 2 minutes, 70°C for Karigane; 60°C for all other green teas. 100°C, 5 minutes for green rooibos tea.

A detailed outline of all green tea packages, their caffeine content and all mild varieties can be found in the article >>Green Tea with Low Caffeine<<.

These packages are supposed to emulate the most potent of all green tea packages, the basic green tea package (Gyokuro, Sencha, Bancha and Matcha) in a milder effect. Since the basic package contains significant caffeine, it is not suitable for everyone. The package is explained in detail in the article >>Green Tea as Medicine<<. While the mild basic package still has quite a potent general effect on health and a significant content of amino acids and catechins; the low-caffeine and low-caffeine package is significantly milder and thus less potent. 

Brewing Time, Infusion and Caffeine Concentration 

A little less common is the question as to whether a short or long brewing time can influence the caffeine content of the tea. For example, could a caffeine-sensitive person better tolerate a cup of Gyokuro in the evening, if a certain brewing time was observed?  The answer is that brewing time indeed determines the caffeine content. Neither a too short nor too long brewing time should be chosen. In general, a brewing time of 2 minutes is quite optimal. Although pouring away the first short infusion is much praised, it does not make much sense to do so. More details here can be found in the article: >>Green Tea Brewing Times and Caffeine<<

Water Temperature and Caffeine Content 

Yet another question remains: does the temperature of the water used to infuse the tea effect the caffeine content? The short answer is yes, though as with brewing time, it is important to optimise the water temperature according to the mix of active ingredients within the tea. By choosing moderate temperatures, significantly less caffeine is actually released than is the case with water over 70°C, for example. This primarily applies in the first 2-3 minutes of the brewing time. Also with a temperature of only 50-60°C, a significant portion of the caffeine is dissolved relatively quickly in the water. If the water temperature in under 50°C however, although there is a lot less caffeine, there is also much less of the other important, healthy active ingredients and still a disproportionately high amount of caffeine. If the water temperature is increased significantly over 60°C, likewise key active ingredients are lost that make caffeine more digestible. The caffeine only becomes chemically unstable at well over 100°C (sublimated from 178°C). The recommendation is generally to use 50-60°C water (70°C for Karigane) depending on the selected tea quality. Higher temperatures and brewing times are sometimes recommended for special applications and illnesses. Further information can be found in the article: >>Brewing Time and Temperature<<

Caffeine in Coffee vs Tea

The health warnings given against the pleasures of coffee and its caffeine are numerous – and not without good reason. Unlike green tea, the caffeine in coffee is not bound to tannin-like polyphenols, such as catechins (= flavanols), but only to chlorogenic acid. Almost all important flavanols are broken down during production through the roasting of coffee beans. In contrast, the tannins contained in tea act like ion exchangers and, as a result, the caffeine is slowly released in the intestinal tract.

Due to the absence of special tannins, the caffeine in coffee enters the bloodstream through the stomach at a higher speed. Because it does not take effect in combination with amino acids, even if a relatively low amount of coffee is consumed, it causes an uncontrolled effect or overdose, and can even produce caffeine tolerance in the nerve cells and withdrawal symptoms.

Due to its lack of attachment to the aforementioned substances, caffeine in coffee reaches the adrenal cortex via the bloodstream. There it triggers the release of the stress hormone adrenaline, which has a strong stimulating effect. In order to break down the adrenaline again, noradrenaline has to be released from the body. The unbound caffeine only has a short-lasting effect. This process is stressful for the body as a whole and costs energy. After this stimulating effect takes place, the body is even more exhausted than before.

Another very important point is that no amino acids exist in coffee (in particular, L-theanine) – as they do in green, white and high-quality black teas – which makes the effect of coffee significantly less tolerable. Various studies have demonstrated that the unique amount of L-theanine in tea allows the general positive health effect of caffeine to unfold.  

Caffeine in Black Tea

This likewise applies to other popular drinks such as black tea and Mate beverages. Here the caffeine reaches the body similarly fast to coffee in a high dosage, since it is not bound to the special tannins found in green tea and is significantly less, to not at all, buffered by L-theanine. In black tea, the catechins are converted into aromatic substances through fermentation. However, it should be emphasised that there is a higher content of amino acids in black tea in contrast to coffee (although this is exceedingly greater in green and white teas). The caffeine in black tea is thus somewhat more tolerable than that in coffee, although still much less so than that in green tea. 

The Special Effects of Caffeine in Green Tea

Since the fermentation of the leaves of the tea plant is stopped during the production of green tea, the ingredients of green and white teas are largely spared from the process of oxidation and the resulting chemical transformations. Thus the caffeine remains bound to the abundant catechins and other polyphenols – unlike in black tea and coffee. Another important difference is the high content of amino acids in green and white teas, especially L-theanine.

This binding, and the combined working of caffeine with the other ingredients present, makes the largest difference between green tea and other caffeine-containing beverages. Because it is bound to tannins, the caffeine in green tea mainly enters the blood through the intestine, and works in interaction with the other valuable ingredients to produce a very mild and long-lasting effect. This allows the extremely healthy benefits of caffeine to unfold very well in the body.

In contrast to the caffeine in coffee, the tannin-bound caffeine in green tea has little to no direct effect on the adrenal cortex. It stimulates the central nervous system, which leads to a much gentler release of adrenaline. Accordingly, noradrenaline is only released gently, if at all. The effects of the caffeine in green tea thus lasts much longer.

Effects of Caffeine According to Tea Quality and Variety

As already described above, the different tea varieties have very different caffeine contents. At the same time, the content of L-theanine, tannins and catechins also varies greatly. This applies not only to the tea varieties, but especially to the different qualities of those variety. High-quality teas have a much more harmonious, richer active ingredient mix than lower-quality teas. In one study, about twice as much L-theanine was found in high-quality Senchas and Matchas as was the case with lower qualities. At the same time, however, the caffeine content in the higher qualities was only increased by 4% and 19% respectively. In the better teas, for example, there is massively more L-theanine available to buffer the caffeine. It is therefore worth investing in quality and selecting the variety according to the requirement, or to consume different teas according to the time of day. More details can be found in the article, >>The Effects of Caffeine According to Tea Quality and Variety<<

Positive Health Benefits of Caffeine

The health benefits of caffeine do not depend solely on the content of the beverage in milligrams (mg), but rather on its interaction and binding with the other ingredients. Numerous studies have pointed to the positive properties of caffeine in green tea. 

It should be emphasised that studies in recent years have highlighted very healthy properties even of caffeine in coffee, which is not bound to tannins (here in particular in the Arabica coffee variety). Studies have shown, for example, the reduced risk of Parkinson’s disease due to caffeine consumed in coffee (1.). Caffeine has also reduced the dopaminergic neurotoxicity of Parkinson’s disease in animal experiments (1, 2). These findings are becoming ever more widely recognised. Of course, this only applies to the consumption of relatively small amounts; the caffeine limit for healthy adults is set at around 300 mg per day.

Through the roasting of coffee beans polycyclic aromatic hydrocarbons (PAH) are created, which have a known carcinogenic effect (3). This is not the case with teas that are not heated to high temperatures. It should be noted however that PAHs are frequently found in tea samples, especially from China, where the teas are heated or roasted in a pan. Fortunately, both coffee and tea are usually only consumed in small quantities, which limits the number of PAHs found in the drink (3). Smoked foods, such as smoked hams, contain much higher amounts of PAHs.

Further significant health effects of caffeine occur in green and white teas, which have numerous extraordinary benefits. Caffeine contributes significantly to the generally excellent health benefits of green tea, as it:

• Increases performance ability and endurance (until 2004 it was even considered a doping substance for athletes, at >12μg/ml in blood)
• Strengthens and hardens the immune system
• Has an antimicrobial effect
• Is a short-term diuretic (however not if taken regularly)
• Produces neither withdrawal symptoms nor dependency

However, if any side effects do occur – such as discomfort, nervousness, stomach upset, or similar – it is recommended to take precautions until the symptoms are tolerable or have completely subsided (see below).  

Side Effects of Caffeine in Green Tea

People react differently to the caffeine in green tea. Although it is bound to tannins and is more compatible with L-theanine, it can still induce significant >>side effects<< ranging from sleeplessness, dizziness, stomach pains to headaches.

Caffeine during Pregnancy and Lactation 

It is generally recommended that no unbound caffeine and relatively little “buffered” caffeine in green tea should be consumed during pregnancy and lactation. Caffeine reaches the placenta unhindered and embryos or infants cannot break it down. In addition, there are a number of other potential risks. This recommendation even applies up to 10 weeks after pregnancy if the mother is breastfeeding. Studies show contradictory results on the caffeine limit, but recent research indicates that caution is advised. The particularly mild varieties Karigane, Sannenbancha and Green Rooibos are recommended. All details and recommendations can be found in the article: >>Caffeine during Pregnancy<<

Caffeine Sensitivity to Green Tea

Over time, the strong health-promoting effects of green tea can improve and significantly reduce caffeine sensitivity to adequate green teas. It should also be noted that green tea, unlike coffee, does not cause caffeine addiction or produce withdrawal symptoms. Nevertheless, in the case of side effects, it is highly recommended not to force yourself into drinking green tea, but to reduce the amount consumed to a tolerable level (still using the correct preparation) and to choose a green tea variety that is more suitable for the respective time of day. It is very important to drink plenty of fresh, still water before and after drinking green tea. People with increased caffeine sensitivity should drink at least the same amount of water. You can find the best advice on how to take in green tea and its caffeine in the article: >>Tips on Using Caffeine in Green Tea”.

Sources

1. 1. Palacios N, Gao X, McCullough ML, Schwarzschild MA, Shah R, Gapstur S, Ascherio A.: “Caffeine and risk of Parkinson’s disease in a large cohort of men and women.“, Mov Disord. 2012 Sep 1;27(10):1276-82. doi: 10.1002/mds.25076. Epub 2012 Aug 27, PMID: 22927157

2. 2. Schwarzschild MA, Chen JF, Ascherio A.: “Caffeinated clues and the promise of adenosine A(2A) antagonists in PD.”, Neurology. 2002 Apr 23;58(8):1154-60. Review. PMID: 11971080

3. 3. Orecchio S, Ciotti VP, Culotta L.: “Polycyclic aromatic hydrocarbons (PAHs) in coffee brew samples: analytical method by GC-MS, profile, levels and sources.”, Food Chem Toxicol. 2009 Apr;47(4):819-26. doi: 10.1016/j.fct.2009.01.011, PMID: 19271317