Will long-term tea drinking lead to calcium deficiency? 6 major rumors about tea, which ones have you fallen into?

Tea is a healthy drink that originated in China and is loved by everyone. However, there are many legends about tea on the Internet, and some experienced tea lovers even believe them.

Below, we have compiled 6 common rumors about tea and analyzed them one by one. Let’s see which ones have misled you.

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1. Drink green tea in summer and black tea in winter

Will drinking the wrong thing harm your body?

This statement has no scientific basis and is a typical "pseudo-scientific proposition" that has misled many people for a long time.

Whether it is black tea, green tea, oolong tea, white tea, dark tea or other types of tea, the raw materials are all fresh leaves of the tea tree. The so-called "different tea trees" are all "the same species" in biology, just different "variety". The types of substances they contain are the same, but the content is different.
Different types of tea, such as black tea and green tea, are mainly processed differently. The difference in their flavors is like the difference between plain Chinese cabbage and hot and sour Chinese cabbage. The flavors of black tea and green tea are obviously different, but the effects of the substances in them on the human body are very small, far from reaching the level of "harming" or "maintaining" the body.

The so-called "green tea is cold, black tea is warm" is mainly a psychological association caused by the taste experience. Green tea has a high catechin content and tastes more astringent. The green and astringent taste makes people easily associate it with "coldness".

Most black teas have a bright red color, which makes people feel red, warm and prosperous at first glance. They are rich in sweet substances and generally not as bitter as green tea. Therefore, the overall feeling of black tea is "sweet and warm".

2. Will drinking tea hurt your stomach?

Experienced tea drinkers often say: "I've been drinking too much ×× tea recently, and my stomach has been damaged and it hurts all the time." This statement also lacks scientific basis.

The human stomach is a solid bag. When food enters the stomach, gastric acid begins to be secreted in large quantities, which can reduce the acidity in the stomach to between pH 2 and 3. There is mucus on the stomach wall, which helps the gastric mucosa to avoid the corrosion of gastric acid and the digestion of pepsin. Tea is weakly acidic, with a pH value between 5.5 and 7. It is far less irritating than gastric acid, and it will not "neutralize gastric acid and affect digestion" as some people imagine.

Tea contains some caffeine, which has a short-term stimulating effect on the central nervous system, thereby promoting the secretion of gastric juice and gastrointestinal motility, and helping digestion. Therefore, some people feel that drinking tea can "scrape away fat and digest food", some people feel mild diarrhea, and some people drink tea on an empty stomach. The caffeine in tea promotes the gastric glands to produce too much gastric acid through the nervous system. Gastric acid will stimulate the gastric mucosa. If there happens to be inflammation or ulcers in the stomach, it will cause stomach pain. Therefore, people with stomach problems or people with a sensitive digestive system should avoid drinking tea on an empty stomach. When choosing tea, try to choose tea with less bitterness.

In summary, if a person's stomach is already damaged, drinking tea, especially on an empty stomach, may make him feel uncomfortable; but if a person's stomach is originally healthy, drinking tea will not cause damage to the stomach.

3. Can drinking tea help you sober up?

Drinking tea cannot help you get rid of a hangover, and there is currently no food or drink that can truly help you get rid of a hangover.

After alcohol enters the body, about 10% to 20% will be excreted through the respiratory tract and skin, and the rest will reach the liver through the blood. Ethanol degrades into acetaldehyde, then from acetaldehyde into acetic acid, and finally decomposes into carbon dioxide and water. The so-called "de-alcoholization" is to speed up this process. So far, no food or drink has been found to achieve this effect.

However, drinking tea after drinking alcohol may alleviate the discomfort caused by drinking alcohol. After drinking a lot of alcohol, people will feel dizzy, weak, and have motor disorders. The caffeine in tea can stimulate the nerves, making the body more excited and awake. To a certain extent, it can alleviate headaches, weakness, dry mouth, and motor disorders, which are "drunk reactions".

However, it should be noted that this "relief" is relative and has limited effect. In addition, caffeine can excite the nerves. Drinking a lot of caffeinated beverages and alcohol will make people less aware of drunkenness, thinking that they are very excited and sober, and continue to drink, which will make people drink more and become more drunk. In serious cases, this situation may be life-threatening. Therefore, it is not recommended to drink tea to sober up, and we also remind everyone not to try things that are not suitable after drinking in order to "relieve the feeling", such as driving, exercising, or operating machinery.

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4. Will long-term tea drinking lead to calcium deficiency?

"Long-term tea drinking or drinking strong tea will lead to calcium deficiency" is a widely circulated statement on the Internet, the reason is that the oxalic acid in tea will inhibit calcium absorption, while caffeine will increase calcium loss. However, this statement is not accurate.

Oxalic acid is widely present in plants, and fresh leaves of tea trees do contain oxalic acid. However, in the process of making tea leaves from fresh leaves, most of the oxalic acid is destroyed. In finished tea, only a few milligrams of oxalic acid can be dissolved into the tea soup per gram of dry black tea, and even less for green tea and oolong tea, only about one milligram. Even if all of these oxalic acids are combined with calcium, the loss of calcium is at most a few dozen milligrams. Compared with the daily calcium requirement of 1,000 milligrams for people, it is so little that it can be ignored.

In fact, people consume much more oxalic acid from vegetables than from tea. For example, to consume 100 mg of oxalic acid, spinach only needs a dozen grams, and lettuce, celery, broccoli, radish, etc. only need a few dozen grams. Compared with the actual daily consumption of vegetables, the oxalic acid intake from drinking tea is not worth worrying about.

Caffeine can stimulate the central nervous system to a certain extent, but there is no evidence that it affects the body's absorption of calcium. Generally speaking, the health benefits of several hundred milligrams of caffeine per day outweigh the possible risks, and a cup of 200 ml of tea contains as little as a dozen milligrams of caffeine, and as much as 50 to 60 milligrams.

Therefore, people who have a normal diet only need to get enough calcium through food diversity and do not need to worry too much about drinking tea affecting calcium absorption.

5. “Washing tea” removes pesticide residues?

In daily life, people often hope to remove pesticide residues by "washing tea", which is actually a taken-for-granted misunderstanding.

The so-called "washing tea" is actually a misunderstanding of a technical method of brewing tea - "warm brewing". If there are pesticide residues in the tea leaves, they are closely bound to the leaves (otherwise they would have been washed away by rain). Letting the tea leaves soak in 100 ml of water for more than ten seconds will have almost no effect on them.

As for green tea, black tea or tea bags, tea polyphenols and caffeine in tea leaves will be dissolved out in large quantities as soon as water is added. Blindly "washing tea" not only fails to wash away the pesticide residues, but also loses a lot of tea essence, which is not worth the loss.
In addition, the impact of pesticide residues on health depends on the total amount of intake. The consumption of tea is generally small, about a few grams to 10 to 20 grams per day. Moreover, tea is drunk by soaking in water, and pesticide residues must be dissolved in the tea before they can be ingested, unlike other agricultural products that are often eaten directly. Therefore, even if you occasionally encounter tea with excessive pesticide residues, the amount of pesticide residues ingested is not very large, so there is no need to worry too much. Of course, it is also recommended that you go to the regular market to buy tea that has been inspected and try to avoid products with excessive pesticide residues.

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6. Is it easy to ingest heavy metals by drinking tea?

If you purchase qualified tea through formal channels, you don’t have to worry too much about ingesting heavy metals.

Heavy metals are pollutants that need to be paid attention to in food. Most tea gardens are located in mountainous or hilly areas far away from factories and cities. They are sparsely populated and transportation is not very developed. Therefore, the possibility of heavy metal contamination is smaller than many other agricultural products.

If the soil in the tea garden is contaminated with heavy metals, the heavy metals absorbed by the tea trees are generally concentrated in the roots, with less distribution in the stems and leaves. In addition, heavy metal elements are basically insoluble in water. Even if the tea leaves contain excessive heavy metals, they are unlikely to dissolve in the tea soup, so there is no need to worry about it.

Of course, from the perspective of food safety supervision, the country has also formulated heavy metal detection standards for tea. If a certain type of tea is found to contain "excessive heavy metals", it means that the tea is unqualified and is not allowed to be sold. It also warns that the soil in the tea garden that produces this tea is "not suitable for cultivation" and needs to be "managed". It does not mean that drinking this tea will immediately cause health problems.

Therefore, when drinking tea, you don’t have to worry too much about whether there are heavy metals in the tea. Of course, it is also right that we tend to choose tea from a good ecological environment. After all, a good ecological environment is not only free of pollution, but also makes tea trees grow better and the tea produced is easier to taste.

Author: Yun Wuxin, PhD in Food Engineering, Science Writer

Review | Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center