Water is one of the most common substances on Earth, an important resource for the survival of all life, including humans, and the most important component of living organisms.
Chinese people like to drink boiled water, because in daily life, people often think that tap water is not good and has a taste. In fact, this is professionally called olfactory taste, including smell, taste and texture, which is a comprehensive sense of the stimulation of sensory peripheral nerves by olfactory substances on the human tongue, nose and mouth, among which smell comes first. Therefore, the Chinese like to boil tap water to drink cold, thus forming a Xi habit, and later, even pure water and mineral water are also Xi used to boil and drink cold.
But in recent years, there has been a saying that "drinking cold white water = chronic suicide", as well as the saying that thousands of boiling water are carcinogenic and overnight water is toxic
First of all, the question of the harm of drinking Liangbai Kai and the toxicity of overnight water can be answered together, that is, whether Liangbai Kai has any effect on the body and how long is the shelf life of Liangbaikai.
In fact, "drink more plain water" is the unanimous recommendation of many food nutrition scholars. In the process of boiling, tap water not only kills bacteria, but also allows some impurities to precipitate, so drinking plain water is safe and affordable.
Experts believe that boiling boiled water has nourished people for thousands of years, and it is also the most healthy water, especially in the morning on an empty stomach to drink a glass of warm water.
So will this cool white open overnight be poisonous. First of all, water does kill a lot of deadly microorganisms when it boils. However, after the temperature of the boiled water drops to room temperature, various microorganisms will continue to enter the boiled water and multiply in the water. The longer the exposure to the air, the greater the number of microbial bacteria. Although the microbial content may be increased, it will not cause much harm to the human body.
Generally speaking, the scene of leaving cool boiled water for a long time is relatively less likely to be infected by microorganisms in the home environment.
Then the so-called "overnight water is toxic", even if the boiling water is left overnight, it will not change the nature of the water itself, and the people say that the overnight water is toxic, generally referring to the overnight water will produce nitrite. Nitrite refers to a class of chemicals such as sodium nitrite, potassium nitrite, and calcium nitrite. Nitrite can interfere with the ability of human and animal red blood cells to carry oxygen, if excessive consumption can lead to systemic hypoxia, ** and mucous membranes appear different degrees of blue and purple, severe cases of irritability, listlessness, unresponsiveness, loss of consciousness, convulsions, coma, respiratory failure and even death, this is nitrite poisoning.
Arguably. Nitrite is indeed a new by-product of drinking water disinfection, but the amount of nitrosamines we ingest from drinking water is actually "minimal".
The Joint Expert Committee on Food Additives (JECFA) of the Food and Agriculture Organization of the United Nations and the World Health Organization (WHO) has established a daily allowance of 0 0 for nitrite2 mg kg body weight, 60 kg people, the daily allowance is 12 mg (when the intake reaches 200 500 mg can cause poisoning, when the intake exceeds 3000 mg can cause death). In the national standard, the content of nitrite in drinking water should be: 1mg l;
In addition, the production of nitrosamine substances requires a suitable environment and precursor substances, but the bacterial substances in the water will lose their activity after boiling, and the nitrate content is small, and there is no basis for producing a large number of nitrosamine substances at all.
CCTV has done experiments in related aspects and concluded that the best drinking period of boiled water is within 48 hours, so overnight water can be drunk with confidence, and it is best not to drink boiled water for more than 3 days.
Of course, it is safest for us to drink "fresh" (i.e. freshly boiled). If you want to prepare cold boiled water, it is best to store it in a clean container with a good seal, so that you can avoid contamination by bacteria in the air, and do not prepare too much at a time.
Let's talk about the problem of a thousand boiling water, a thousand boiling water, that is, water that has been boiled for a long time (repeatedly boiled). It is rumored that drinking such water can cause cancer, and the basis for this is mainly the "nitrate and nitrite" substances contained in it. In fact, in the process of repeated boiling of water, due to the problem of high temperature and lack of oxygen, it will indeed cause some nitrate substances in the water to be converted into nitrite.
CCTV's "Into Science" column has invited the Guangdong Provincial Food Inspection Institute to do relevant experiments, through ion chromatography experiments, which is a method of separating, qualitatively and quantitatively separating a variety of anions or cations that coexist continuously by using the principle of ion exchange. The test results show that there is indeed an increase in nitrite in Qianzhuan water, but this content is relatively small, and its value is far below the national standard, and it cannot be generalized, so there is no connection between Qianzhuo water and cancer poisoning.
According to CCTV, tap water was repeatedly boiled 18 times and then overnight for 1 night, and the nitrite produced only reached 1% of the national limit.
Other scientists have done related research experiments, and the nitrite content of boiling water after repeated boiling for 20 times is: 0038 mg/l。Therefore, it is safe to drink the water that has been boiled several times in life, and it will not cause cancer.
One of the real carcinogenic risks is hot water, which is more than 65% to be exact. If the temperature is too high, it may cause a certain degree of thermal damage (such as burns) to the mucosa of the digestive tract, and the surface layer of the damaged mucosa of the digestive tract will be peeled off and renewed.
For these reasons, the International Agency for Research on Cancer (IARC) classifies very hot beverages above 65 as Group 2A carcinogens
In addition, although water is closely related to our health, but it is not advisable to drink too much water, excessive drinking water can even be life-threatening, according to the recommendations of the Dietary Guidelines for Chinese Residents (2016 Edition), adult men should drink more than 1700ml of water per day, adult women should drink more than 1500ml, if a glass of water is calculated as 200ml, it is about eight cups of water.
China's Health Commission recommends that children aged 7-10 need to drink 1000ml of water per day, children aged 11-13 need to drink 1100-1300ml of water per day, and adolescents aged 14-17 need to drink 1200-1400ml of water per day.
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