10 Mar 2016

Coffee vs. Tea // part IV

(Part I)
(Part II)
(Part III)

Welcome back. Now that we've chosen our favourite taste and also know how to make it available in a drink, the next questions might come up: What is even happening when you drink it? What do you get from it? What do you not get? Or does it take something from you? I'll start with some subjects concerning both drinks equally.

As it's even named after it, caffeine seems to be a rather important content in coffee. But tea also contains caffeine, sometimes matchingly called theine then.

First of all, let's get a quick overview of what it even is. Caffeine is infact considered a psychoactive drug, since it works as a stimulant for the central nervous system. It has several quick effects on the body, most known is its ability to block adenosine receptors. Adenosine basically is used by the brain to remind itself of not overexert and can be experienced as tiredness and fatigue. So caffeine invalidates this, and makes you less likely to notice your level of exhaustion. Many drugs or pharmaceuticals work in similar ways, and when regularly used, lead the brain to increase the amount of affected receptors in order to reconstitute the neurotransmitters' function. You experience this as an dependency or addiction. The same amount of caff won't do the job anymore, as your brain is "keeping that in mind" already, and you have to drink more to get the desired effect again. And without any intake, your brain will unintentionally make you feel more tired than appropriate due to all the extra adenosine receptors.

Yes, you do pour the caffeine right into your synapse.

Other effects are increase of heart rate and overall physiological activity, better concentration, activation of the alimentary system and reduction of existing headache (also prone to addiction!) Subsequently, you can also sort of overdose caffeine, resulting in over the top versions of the desired effects. A lethal dose can not realisticly be achieved via consumption of drinks though, this is possible only with the pure chemical.

Coffee has more caffeine per serving than tea. I've heard that double the amount of tea is usually needed for the same amount of caffeine, but both plants really vary in the amount depending on the cultivar. What also matters a lot is how you prepare the drink. Filter coffee for example contains more caffeine than espresso, although you might expect it to be the other way round. For tea, the different types already give very different levels and bioavailability of the stuff. Red/black tea for example seems to have more caffeine than green, but actually it's just less bound to other contents due to the oxidation process and thus kicks in faster than the same amount in green tea. And then you also get different amounts extracted depending on dose and time of course. In any case, in coffee it's even more bioavailable.

Water balance.
You often hear that both coffee and tea dehydrate your body, so you have to drink additional water to counter that loss. As said above, caffeine gets your digestive system going. This may well result in your body releasing more water for the moment, but it doesn't mean you lose more in the long run. I daresay that having a well-tasting hot beverage, probably even a whole pot of it, could actually bring people to drink more than if that would be just water. So they can infact both be counted to your fluid balance. They better do, because in Germany, people on average drink more coffee than water, and many other peoples should also be long parched because of their tea consumption if this wouldn't work.

Neither of the two drinks contain any relevant amounts of carbohydrates, fat or protein. This may also be a reason for their popularity, since you get effect and enjoyment without these dreaded calories.

The following statements mostly cannot be relied on fully. Many studies are performed about all the subjects, few findings can really be seen as safe and the general opinion often changes.

Polyphenols are antioxidants contained in many plants, and can usually be seen or tasted, for example as bittern or tannine. They are said to reduce cell aging, cancer risk and arteriosclerosis. I also heard that they can prevent hair loss. But polyphenols also tend to inhibit certain minerals and nutrients absorption in the gut, so it's recommended to wait around half an hour between drinking those and having a meal. There's much more of them in tea, especially in green (unoxidized) tea. When combining your drink with milk, you foil the polyphenols' effects, so consider drinking it pure!

Now to some differing contents.

Brewed (filter) coffee doesn't contain much of anything else useful seemingly. Just caffeine, aromatic substances, water and really small traces of minerals etc.
Espresso however has much more TDS, total dissolved solids, and thus has something more to offer. Given that one shot weighs about 40g, you get around 7% of the daily recommended amount of vitamin B2, and around 14% of B3. Also, there's about 9% of the daily needed magnesium in a shot.

A popular belief is that coffee consumption is related to heart attack risk and similar problems. This is outdated. Instead, it could possibly even increase vascular function. Other possible benefits include a reduced risk of type 2 diabetes and prostate cancer, whereas the somewhat popular ability of Alzheimer's prevention has not been confirmed surely.
On the negative side, there's mainly the much likely caffeine dependency, showing as headaches, sleep disturbances and mood unstableness or even depressiveness. Further, the acidity of the drink, especially present when roasted (too) hot and short (-> very dark), can cause pyrosis.

Per 100g of beverage, you get around 10% of the daily needed amount of manganese and, as stated above, way more polyphenols than with coffee. When you consume the whole leaf material, as when drinking Matcha, you also get around 1% of the recommended iron dose, this could be not so useful due to the polyphenols though. There are some implications of cancer reducing effects all currently in question. Tea can slightly reduce blood pressure as well as levels of bad cholesterol, thus working to prevent heart attacks. Weight loss is not a confirmed effect though.

Camellia tends to absorb more fluoride from the soil than other plants. Especially in mature leaves, there are quite high concentrations subsequently. Fluoride locally promotes dental health, but can cause bone and tooth fluorosis and thus lower stability when consumed too much. Especially Pu Erh tea and mature leaf red/black tea can already bring about the maximum recommended daily intake of 4mg within one litre.
Another possibly negative content is oxalate, which binds calcium in the body and makes it unavailable, and can also cause kidney stones. However, the bioavailable amount of oxalate consumed with tea is low and the negative effects are probably not relevant at all.

I think these are the most important health aspects and contents. In the next part, I'll give you a summary and maybe draw some conclusions.

Thanks for reading!


  1. Tea also contains L Theanine which tends to reduce stress, encourage relaxation, and counters some of the side effects of caffeine. Overall, this is why a tea buzz is much less jittery that a coffee buzz.

    1. Thanks for the addition Marty. I felt this to be sort of included in the difference in bioavailability!