Drinking tea is a simple and ordinary thing, but there are always some people with ulterior motives who make waves and spread rumors to see if you have been fooled by these rumors.

Overnight tea is easy to cause cancer.

There is a saying that "overnight tea is poisonous as a snake". Some people swear that some secondary amines in overnight tea can be converted into carcinogenic nitrosamines. Never drink overnight tea!

Of course, it is good not to drink overnight tea, but this statement is somewhat exaggerated.

First of all, secondary amines are not unique to overnight tea, but are found in many foods, and the content in tea soup is far lower than that in any staple food or vegetable.

Secondly, the formation of nitrosamines requires specific conditions, which does not mean that tea soup containing secondary amines and nitrates will definitely form nitrosamines.

3. Carcinogenic conditions: intake of nitrosamine 100~200mg per kilogram of body weight, and continuous high-dose administration. Even though overnight tea may contain nitrosamines, the content is not enough to cause such great harm.

Therefore, we should not be too nervous about the theory that overnight tea causes cancer. Of course, but this does not mean that overnight tea is hygienic and safe, because the tea soup may breed harmful microorganisms and cause the tea soup to deteriorate if it is left for a long time. Therefore, although overnight tea can't cause cancer, it's better not to drink it.

Tea scale causes cancer.

Tea scale is often the protagonist of "carcinogenesis". Some people say that tea scale contains cadmium, arsenic, lead and mercury, which is easy to induce cancer.

First, let's take a look at how tea scale is formed.

Tea scale is formed by the oxidation of tea polyphenols and metal elements in tea rust after tea leaves have been placed for a long time.

Tea scale does not cause cancer for two main reasons:

The first is the dose problem. Expert testing shows that only trace lead and mercury are detected in tea scale, and arsenic and cadmium are zero, indicating that it is highly carcinogenic.

Second, DNA has the ability to repair. Although low-dose carcinogens can damage DNA, due to our own protection mechanism, DNA can automatically repair minor damage without causing harm to human body. Therefore, the theory that tea scale causes cancer is somewhat exaggerated. However, from a health point of view, it is better to wash tea stains often.

Gout patients can't drink tea, which will form tophi.

Supporters of such rumors believe that the molecular structure of caffeine and theophylline in tea is methylxanthine, which can be converted into uric acid after metabolism in the body.

Well-founded, convincing, right?

However, a large number of studies have found that methylxanthine will become methylurate after metabolism in the body, which, unlike urate, will not be deposited in joints and will not form tophus.

Moreover, because tea is weakly alkaline, moderate drinking can alkalize urine and promote uric acid excretion. Therefore, gout patients can drink light tea in moderation.

Drinking tea can reduce weight and detoxify.

Drinking tea can relieve boredom, promote digestion and help to reduce fat to some extent, but don't expect to lose weight after drinking a few cups of tea unless you only drink tea instead of eating. Moreover, people who drink tea get hungrier and hungrier, forming a vicious circle.

If you want to lose weight, remember those six words: shut up and take your legs.

"Drinking tea to detoxify" was probably put forward by the people in the WeChat business.

Detoxification mainly depends on the human immune system. For example, the liver has a certain detoxification function, and the kidney can discharge the waste of human metabolism. So, don't put so much pressure on tea, it really can't detoxify.

Don't drink tea at night, or you will lose sleep.

This is a widely circulated saying that drinking tea sometimes does affect sleep, but it is not absolute.

Because everyone has different tolerance to caffeine, it doesn't mean that drinking tea at night will lead to insomnia.

For example, many old tea drinkers have a high tolerance for caffeine and can sleep soundly even if they drink tea at night.

In addition, black tea, black tea and old tea with years have relatively weak nerve stimulation.

The fresher the tea, the better.

This is mainly for spring tea. There should be a freshness here, not the fresher the better.

The freshly picked spring tea contains a lot of unoxidized polyphenols and aldehydes, which has a strong stimulating effect on gastrointestinal mucosa.

Moreover, the caffeine and aroma content of new tea is also high, which is easy to stimulate the nervous system, thus causing insomnia and tea drunkenness. Therefore, fresh spring tea (including green tea) is best left for about half a month before drinking.

Black tea can nourish the stomach.

In fact, no kind of tea can be said to really "nourish the stomach", but different teas stimulate the stomach differently.

Black tea has the function of warming the stomach because of its mild nature, but it warms and nourishes the stomach.

No matter what kind of tea, it contains caffeine and tea polyphenols, which can promote the secretion of gastric juice.

Although some teas (black tea, Pu 'er cooked tea, old white tea, etc. ) will reduce the content of tea polyphenols, it is difficult to reduce the content of caffeine.

What the stomach is most afraid of is food that is too alkaline. Once alkali is injected, the function of gastric acid will naturally decrease, which is a destructive blow to the digestion and absorption of human body. Caffeine in tea can cause stomach burns.

If tea can nourish the stomach, then there must be ingredients or other theories. Without these, as far as the basic ingredients contained in tea are concerned, there is no element that can nourish the stomach.

Drinking tea can lead to iron deficiency anemia

According to Life Times, taking black tea extract or drinking strong tea may reduce the iron absorption rate. But if the tea you drink is not particularly strong, it will not affect the absorption of iron.

At the same time, the study also shows that these iron must be "non-heme iron" to be affected by tea-that is, the iron in pork, beef, mutton, fish and other foods will not be affected, only the iron in plant foods such as fungus and celery will be affected. And if vitamin C is supplemented, this negative effect can be partially eliminated.

Drinking tea leads to osteoporosis.

There is a saying that tea contains more caffeine, and caffeine has diuretic effect, which can promote excessive urinary calcium excretion, leading to negative calcium balance and calcium loss.

I consulted Zhang, the attending physician of the First Hospital of Yuhang District, Hangzhou. He said that drinking a lot of tea, especially strong tea, may cause calcium loss.

Therefore, drink tea in moderation first, and then don't drink strong tea.

Professor Tu Youying from the Tea Department of Zhejiang University suggested that the daily consumption of tea for adults is usually 5- 15g dry tea. The total water consumption for making these teas can be controlled at 400- 1500ml. Of course, if you drink Yunnan tea, you can reduce the amount of tea appropriately because of its rich endoplasm.

Tea foam is poisonous, don't drink it.

When making tea, we often see tea foam, which many people think is pesticide residue or toxin. In fact, foam is tea saponin in tea.

Tea saponin in tea is a small amount, which will not affect the taste when drinking tea, but now there are special technologies to extract it and use it as emulsifier, detergent, foaming agent and so on. It can be seen that the foam caused by tea saponin is harmless to human body.

Tu Yu in Wei and Jin Dynasties wrote a poem: "Foam becomes a floating flower, rejuvenation is like snow, and leaves are applied in spring." It seems that in ancient times, people still regarded tea foam as a kind of essence.

Mixed tea is adulterated tea.

Let's take a look at what blending is, which mainly includes: grade blending, origin blending, tea seed blending, season blending, year blending, and different technology blending.

The reason for blending is to learn from each other's strong points, improve the level and fullness of taste, and achieve a balanced and harmonious taste and nutrition. For example, the national team selects players from various clubs in order to let them play their respective strengths, work as a team and play their strongest fighting capacity. So there is an essential difference between matching and adulteration.

Washing tea can remove pesticide residues.

First of all, the vast majority of pesticide residues in tea in China meet the national standards.

China's "Maximum Residue Limits of Pesticides in Food" stipulates 48 requirements for pesticide residue limits. Those who meet this standard will not cause harm to the human body. Moreover, according to the inspection report of 15000 tea samples by the National Tea Quality Supervision and Inspection Center, the overall qualified rate of pesticide residues in tea samples is higher than 96%. This shows the quality and safety standards of most teas in China.

In addition, water-insoluble pesticides are used in the process of tea planting, and there will be no pesticide residues in the tea soup. From the point of view of avoiding pesticide residues, it is unnecessary to wash tea.

Moreover, high-quality green tea, yellow tea and black tea, because the buds and leaves are tender, all kinds of endoplasm are leached quickly in water, and a large number of nutrients are lost in tea washing, which affects the taste of tea. Washing tea is not recommended.

Where there are people, there are rumors, and rumors are broken. I hope everyone can have tea with peace of mind and let the rumors stop at the wise.

References:

[1]. There is no scientific basis for overnight tea to cause cancer, Jiang Heyuan, Health Hall;

[2]. "Tea dirt can cause cancer. Is it really that toxic? Jiang, a bridge between doctors and patients;

[3]. Nine Taboos for Gout Patients to Drink Tea, Miao Zhimin and Li Changgui, Healthy Things;

[4]. There are many rumors in the tea circle. How much do you know? 》

[5]. "Smash rumors and clarify the right and wrong of" tea ",Ma Zhiying's Nutritional Food;

[6]. "Drinking tea at night will definitely lead to insomnia?" Zhu, True and False Health.