Can boiling water cause cancer?

2022-09-25

Water is an indispensable nutrient for human beings. Some people claim that "a thousand boiling water is cancer-causing!" and "overnight water is poisonous and must not be drunk", which caused panic and doubts among the public.

So, are there any basis for these claims? How to drink water more safely and healthily?

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Does drinking a thousand boiling water really cause cancer?

Thousands of boiling water, that is, water that has been boiled for a long time (repeatedly boiled). It is rumored that drinking such water will cause cancer, and the basis for it is mainly the "nitrate and nitrite" substances contained in it. In fact, in the process of repeatedly boiling water, due to the problem of high temperature and lack of oxygen, some nitrates in the water will indeed be converted into nitrites.

But does containing nitrite mean that it will cause cancer?

After experimental determination, the nitrite content in tap water is 0.007 mg/L, the value after boiling once is 0.021 mg/L, and the content after continuing to boil 20 times is 0.038 mg/L.

The nitrite content in drinking water is limited by a clear "national standard", and the nitrite value is ≤1 mg/L; in other words, to reach this limit, theoretically, the water needs to be boiled 200 times .

Therefore, even after being boiled many times, the value is still far below the national standard. In fact, drinking a thousand boiling water has no connection with cancer.

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Is drinking overnight water really toxic?

Some people say that drinking water overnight is toxic and even causes cancer. The reason is still the problem of "nitrite". Nitrosamine compounds are indeed a new type of drinking water disinfection by-products, but the content of nitrosamines we ingest from drinking water is actually "minimal".

Because the production of nitrosamines requires a suitable environment and precursor substances, but after the water is boiled, the bacterial substances in it will lose activity, and the nitrate content is less, and there is no basis for producing a large amount of nitrosamines.

Therefore, even if the boiled water is left overnight, it will not change the nature of the water itself, and the microbial content may increase, but it will not cause great harm to the human body.

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How to make drinking water safer and healthier?

1. As long as the water you drink is clean, qualified and safe, you can drink it with confidence.

2. Drinking water, don't stick to drinking "8 glasses of water". The size of the cups is different, and the amount of water you drink will naturally be different.

The "Dietary Guidelines for Chinese Residents" recommends that adults drink 1500-1700ml of water a day. Please calculate the "number of cups" according to the size of the cup; in addition, if the weather is hot or some special groups (outdoor workers, athletes, etc.), You should also increase your water intake appropriately.

3. Don't drink "raw water".

When drinking water, pay attention to hygiene and ensure it is clean and safe; many people are accustomed to drinking tap water that has not been heated and boiled, but such "raw water" may contain harmful substances such as chlorine, bacteria, and insect eggs. So, please boil it before drinking.

4. Do not drink hot or ice water, and the water temperature should be "appropriate".

Drinking ice water will cause the gastric mucosa to suddenly become cold, causing capillaries to constrict, which will cause gastrointestinal discomfort; drinking hot water will undoubtedly damage the mucosa (esophagus, stomach), and even increase the risk of gastrointestinal cancer.

Therefore, the water of about 37 degrees Celsius is the most reliable, which is equivalent to the body temperature, and the human body will accept it more.

5. Drink slowly, do not "drink a lot of water at one time".

Don't worry about drinking water, "drink slowly", refuse to drink a lot of water at one time when you are thirsty, and drink no more than 500 ml of water at a time, and refuse water poisoning. Take small sips of water, about 200ml each time, slow down and drink slowly.

6. Don't wait until you're thirsty to drink water.

For various reasons, many people always like to wait until they are thirsty before drinking water, but at this time the body is already seriously dehydrated, which poses a great threat to the body's metabolism.

Therefore, develop a good habit of drinking water, and drink a small amount of water deliberately after getting up, before eating, and before going to bed.

7. Treat advertisements reasonably, don't be obsessed with "conceptual water".

There are all kinds of "gimmick water" on the market, and concepts such as oxygen-enriched water, alkaline water and ecological water emerge in endlessly; in fact, more of them are just "publicity gimmicks". In contrast, boiled water is more affordable and reliable, and there is nothing magical about "concept water".