Are you Team Coffee or Team Tea?
After water, coffee and tea are the most consumed beverages in the world. They are also excellent sources of caffeine and antioxidant polyphenols. Learn about the health benefits and drawbacks of consuming coffee and green tea in this article.
Coffee is obtained from the coffee bush (lat.: Coffea arabica) and contains more than 1000 biologically active substances. The best known substances, which are found in higher concentrations in coffee, are caffeine, chlorogenic acid and diterpenes [1]. In the Western world, coffee is the most commonly consumed stimulant, along with alcohol, nicotine and sweets, and is particularly valued as a wake-up or stimulant [1]. And the nice thing is that while alcohol and nicotine are poison for the body and sweets damage weight and teeth, coffee has a lot of positive aspects. You’re about to learn why.
Caffeine is responsible for the stimulating effect of coffee. Caffeine binds to certain receptors on nerve cells and blocks them. As a result, other molecules can no longer bind. The result: the brain can no longer receive the signal “tiredness” and we stay awake longer.
Teas like green, black or white tea are made from the leaves of the tea bush (lat.: Camellia sinensis). The leaves of Camellia sinensis also contain caffeine and other well-known secondary plant compounds such as cathechins, chlorogenic acid or rutin [1, 2]. However, the effect of caffeine from tea is usually weaker because the caffeine is bound to the tannic acids that are also found in tea and can therefore be absorbed in the intestine more poorly and, above all, more slowly. Unlike coffee, tea therefore does not make us awake.
The most important effects of green tea
In addition to the caffeine found in tea, there is much discussion about the effects of certain other ingredients — the so-called polyphenols.
The most important polyphenols here are the cathechins, especially epigallocathechin gallate (EGCG), which is found in green tea. The intimidatingly long and chemical name of this substance is not only perfect for the next round of gallows guessing, it shouldn’t scare us off: studies have shown that EGCG has a wide range of health-promoting properties. Through its strong antioxidant effects, EGCG can scavenge harmful radicals created in the body and additionally reduce inflammatory processes in the body [1, 2].
Larger studies also showed that green tea consumption can lower blood pressure, blood sugar, as well as blood lipids (total cholesterol and LDL cholesterol, which is harmful to health), and improve insulin resistance. This reduces the risk of type 2 diabetes, metabolic syndrome, or cardiovascular diseases such as a heart attack or stroke [1, 3, 4, 5, 6, 7, 8, 9].
The blood sugar-lowering properties of green tea probably come from the abilities of some polyphenols to inhibit the absorption of glucose in the intestine. In addition, it promotes the uptake of glucose from the blood into cells and reduces the production of endogenous glucose in the liver [2].
A Japanese study also showed that consumption of at least 4 cups of green tea per day was associated with a 51% reduced risk of suffering from depressive symptoms [10].
Green tea is also said to have an antitumor effect — that is, an effect that inhibits tumor growth. However, these effects have so far been shown mainly in cell and animal studies, whereas the results from human studies are less consistent [11].
In addition to the most important polyphenol EGCG, chlorogenic acid and rutin, among others, are also found in green tea. Chlorogenic acid — which is also found in larger quantities in coffee — is characterized by a high antioxidant and anti-inflammatory potential as well as a blood sugar-lowering and antitumor effect [2, 12]. Rutin, which is found in particularly high concentrations in matcha tea, also has antioxidant and anti-diabetic properties [2, 13].
However, in addition to the multiple beneficial properties, it is important to realize that the data remain inconclusive on some points. For example, some studies show positive effects of green tea on blood glucose levels, while no effect was found in other studies [14].
Green tea extracts as a safety risk
The many positive effects of green tea sound fantastic. But wouldn’t it then be much easier to take the health-promoting polyphenols such as EGCG as a high-dose extract instead of drinking larger amounts of green tea?
In fact, taking green tea extracts is heavily promoted and therefore increasingly popular. But studies showed that high-dose green tea extracts — in contrast to green tea as a hot drink — produce a negative effect and should therefore not be recommended. Damage to the liver is particularly prominent: from slightly elevated liver values, the intake of high-dose green tea extracts can even lead to liver failure and liver transplantation [3, 15, 16].
The extracts contain high doses of cathechins, which can also interact with certain drugs such as statins, beta-blockers, or imatinib, which is used in cancer therapy [17, 18, 19].
The most important effects of coffee
Besides caffeine, chlorogenic acid is the best-known ingredient in coffee. The positive effects of coffee on our health are partly attributed to chlorogenic acid. Chlorogenic acid has high antioxidant, anti-inflammatory, anti-diabetic as well as anti-tumor potential. There are different possibilities as to how the blood sugar lowering effects of chlorogenic acid come about: one explanation is that chlorogenic acid slows gastric emptying and inhibits the absorption of glucose in the intestines. As a result, less glucose enters the bloodstream and blood glucose levels do not rise [20]. Other studies showed that chlorogenic acid as well as other polyphenols of coffee cause glucose to be absorbed faster from the blood into the cells as well as inhibit the production of endogenous glucose in the liver. This leads to a decrease in blood glucose levels [21, 22, 23, 24].
Scientific studies have shown that coffee consumption has protective effects against a number of diseases, such as type 2 diabetes or liver dysfunction [21, 25, 26, 27]. In addition, coffee consumption is also associated with a lower overall mortality risk and a lower risk of developing or dying from cardiovascular diseases such as myocardial infarction, heart failure, or stroke [1, 25, 28].
Coffee is also said to have an antitumor effect: the risk of liver cancer is reduced by coffee consumption. The risk of other liver diseases such as non-alcoholic fatty liver disease (NAFLD) also decreases [25, 27, 29]. In addition, the risk for neurodegenerative diseases such as Parkinson’s disease is also lower [26, 27, 30].
Coffee as a health risk?
When you see the many positive effects of coffee on our health, you might think that coffee is a real all-rounder for our health. But is that really true?
In addition to caffeine and chlorogenic acid, coffee also contains diterpenes (cafestol, kahweol). Diterpenes increase cholesterol levels — especially LDL cholesterol, which is harmful to health — and can therefore pose a risk, particularly for people with a lipometabolic disorder. However, diterpenes are filtered out in the coffee filter, so that only unfiltered coffee (e.g. French Press, Turkish coffee) contains diterpenes in higher amounts [26].
The European Food Safety Authority (EFSA) considers a caffeine intake of 200 milligrams as a single dose (approx. 2 cups of coffee) or 400 milligrams distributed over the day (approx. 4 cups of coffee) to be safe for healthy adults. For pregnant and lactating women, half is considered safe for mother and child [31]. In higher amounts (from about 400 milligrams of caffeine, i.e. 4 cups of coffee) and for those sensitive to it, caffeine can also cause sleep disturbances and anxiety. High amounts of caffeine can also increase the risk of miscarriage and negatively affect the growth of the unborn child. Therefore, coffee should only be consumed in moderation (approximately 200 milligrams of caffeine throughout the day) during pregnancy [26].
Team coffee or team tea?
Whether you’re on Team Coffee or Team Tea, for healthy adults, both coffee and tea can generally be considered beneficial to health. However, it depends on the method of preparation: if you drink your tea or coffee with a lot of sugar or sweeteners, there may be fewer positive effects on your health — certainly not on your risk of diabetes [26]. If one drinks one’s coffee or tea with milk, this can also have negative effects. The bioavailability of the health-promoting polyphenols is reduced by the milk, which is why one should drink both coffee and tea black if possible [32]. Due to the substances in coffee and tea that are rather detrimental to health, both should only be consumed in moderation. As Paracelsus already knew: the dose makes the poison.
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