Is there a calcium deficiency in drinking pure water? Purified water: Thank you, just hydrate

Source: Voice of China, China Central Radio and Television Corporation

This week, March 22-28, is the 34th "China Water Week".

Water, water and all things. Human beings cannot survive without water. Generally speaking, a healthy adult needs to supplement about 3,000 ml of water every day, which not only includes the water that is directly drunk every day, but also the intake of soup, porridge, fruits and vegetables, and the metabolic water produced by the human body. The 2016 edition of the Dietary Guidelines for Chinese Residents recommends drinking enough water for adults to 1500 to 1700 ml per day.

Drinking water is so important that many rumors have also focused on drinking water.

There are rumors that "drinking 'overnight water' and 'thousand boiling water' has a risk of carcinogenicity", "drinking 4 liters of water a day will be poisoned", "drinking pure water will be deficient in calcium", "drinking water with more scale is prone to kidney stones"... How much credibility are these claims?

"Drinking 'thousand boiling water' often has a carcinogenic risk"?

Experiments show that the value of nitrite in boiled water 20 times increases, but it does not exceed the limit.

Strictly speaking, "overnight water" and "thousand boiling water" are not very clear definitions. It can be roughly understood that when the eyes are closed before going to bed, the eyes are opened when they wake up, and the same cup of water they see is "overnight water"; once the water is turned on, it is extinguished, and then it is turned off again, and several times down, it is "thousands of boiling water".

For their carcinogenic risk, they all point to the same "murderer" - nitrite, saying that these two types of water will produce a large amount of nitrite, so it is believed that drinking too much has a carcinogenic risk.

Usually, the amount of nitrite that can cause acute poisoning in humans is between 0.2 and 0.5 grams, and ingestion of more than 3 grams can cause death. China's "Drinking Water Sanitation Standard GB5749-2006" stipulates that the limit value of nitrite per liter of drinking water is 1 mg per liter.

What will be the nitrite content in "overnight water" and "thousand boiling water"?

The residue testing room of Harbin Customs Technical Center has conducted experiments on this. Wei Dongxu, director of the testing room, introduced that the nitrite content in normal tap water is about 0.002mg/L, and experiments have shown that the nitrite content of the boiled water is about 0.005mg/L after being placed overnight for 24 hours; after boiling 20 times, the value of nitrite in the water will reach 0.371mg/L, which is about 180 times higher than the original value.

It can be seen that after 24 hours, the nitrite content in the water has increased, but the value is lower than the poisoning dose; and after boiling 20 times, the nitrite value in the water is significantly higher than the initial value, but it is still lower than the limit value in the "Sanitary Standards for Drinking Water".

Despite this, Li Yuze, director of the Clinical Nutrition Department of Heilongjiang Provincial Hospital affiliated to HIT, still advises everyone not to boil the water repeatedly.

Li Yuze said: "Nitrite is a substance that can cause food poisoning, and it is not possible to examine the toxicity without the dose. The human body may pay some minerals and trace elements in order to metabolize these substances. If it is a patient whose liver function has been impaired, it is even more important to be careful.

"Drinking 4 liters of water a day can poison"?

4 liters is not a "red line", be wary of drinking water in a short time

Water poisoning can indeed occur. A woman in Shenzhen has been reported to have drunk 3.2 liters of water at one time in order to do the examination, and as a result, she has symptoms such as nausea and vomiting, convulsions of hands and feet, and has been diagnosed with "water poisoning".

However, the figure of 4 liters is not a "red line".

In fact, the human body's demand for water depends on the environment, exercise, physical condition and food intake of each person, and there is no definite standard value. It's a bit like "drink 8 glasses of water a day", is it a bullet cup or a larger thermos cup?

The so-called water poisoning is generally caused by drinking a lot of water in a short period of time. Ruan Guangfeng, director of the Science and Technology Department of the Science and Technology Exchange Center of Kexin Food and Nutrition Information Exchange Center, said that this is mainly related to the metabolic capacity of the human kidneys: "The kidneys of healthy people can normally discharge about 800-1000 ml of water per hour, and the kidneys can metabolize normal drinking water within this degree." However, if you suddenly drink a lot of water in a short period of time, the kidneys may not be able to excrete it in time, exceeding the metabolic load. Then, excess water will enter the cells in large quantities and cause hyponatremia. ”

So, what to avoid is to drink water in a short period of time.

So, how much water do you have to drink in a day?

The 2016 edition of the Dietary Guidelines for Chinese Residents recommends drinking enough water, 1500 to 1700 ml per day for adults, and advocating the consumption of boiled water and tea; not drinking or drinking less sugary drinks.

 "Drinking water with more scale is susceptible to stones"?

"Drinking pure water will cause calcium deficiency"?

Drinking water: I just have to make up the water

Ruan Guangfeng introduced that the water with a lot of scale is mainly its hardness and high content of calcium and magnesium ions: "Ordinary people drink about 2 liters of water every day, of which the calcium content is about 100 mg, which is far less than the content in a cup of milk." ”

Stones are caused by imbalances in the body's metabolic balance. On the contrary, drinking too little water every day, too much purine intake is more likely to stone.

This rumor is worried about calcium in the water, and that one is worried about not having enough calcium in the water. There are rumors that "drinking pure water will cause calcium deficiency".

Tap water, pure water, mineral water, other drinking water, etc., there are many types of drinking water, each with its own advantages and disadvantages. However, their main role is one, that is, to hydrate and provide water to the body, and pure water is no exception.

The source of calcium in the human body is mainly provided by diet.

As mentioned earlier, drinking water also contributes to minerals such as calcium, but there are large differences according to water quality, and this amount is significantly lower than the calcium content provided by the diet. That is to say, in the matter of calcium intake, more it is not more, less it is not more.

Producer 丨 Liang Yue

Reporter丨Liu Fei Wang Xue

Editor 丨 Yang Yang