In fact, except for a few brands such as Nongfu Spring and Evian, most brands of bottled (barrel) drinking water sold in the market are not marked with pH value, which makes consumers unable to distinguish when purchasing.
So, what is the pH value in the water? What does it have to do with human health? How to choose healthy drinking water? In response to the concerns of these consumers, a few days ago, the reporter interviewed Dr. Zhou Li, deputy director of Hangzhou Yangshengtang Research Institute.
PH value is one of the most important water quality parameters.
According to Dr. Zhou Li's introduction, and summarizing the discussion of water experts and authoritative documents at home and abroad, healthy drinking water has three characteristics: first, it contains a certain amount of hardness (the sum of calcium and magnesium ions); Second, it contains a certain amount of dissolved total solids (the sum of minerals in water), that is, it contains comprehensive and balanced natural minerals and trace elements needed by the human body; Third, the pH value is above 7.0, which is weakly alkaline.
He said that there are many water quality indicators, among which pH value is one of the most important water quality parameters. The pH value of water is expressed by pH value. Generally, the pH value of natural water source is 6.5 ~ 8.5. The influence of acidic substances (including most organic pollutants) or acid rain will reduce the pH value of water to about 5.
As we all know, generally speaking, water can be weakly ionized, that is, a hydrogen ion and a hydroxide ion are produced. Traditionally, we take the negative logarithm of hydrogen ion concentration as the index of the acidity and alkalinity of the solution, abbreviated as pH. In neutral solution, pH=7, the more pH is greater than 7, the stronger the alkalinity, and the less pH is less than 7, the stronger the acidity. In pure water and artificial mineral water, both of them are acidic due to excess hydrogen ions, and some artificial mineral water is even more acidic than pure water.
In some publicity materials, even in some popular science articles about water, it is said that "the pH value of normal human body should be weakly alkaline". Dr. Zhou Li said that what we usually say about the human body's pH value is 7.35~7.45, which means the pH value in human blood, and the pH value in different parts and tissues of the human body is different. In order to carry out normal physiological activities, the concentration of hydrogen ions in blood must be maintained within a certain normal range.
However, the normal concentration of hydrogen ions depends on the regulating function of the human body, so that the pH value in the body can reach a dynamic balance. Overacid or overbase can cause the change of blood hydrogen ion concentration, which makes the normal acid-base balance disorder, which is called acid-base imbalance for short. For example, when hungry, the pH value of gastric juice 1~2, skin 5.5, large intestine 8.4, sweat 6.0 and urine 6.9. No matter where, the pH value is maintained in a constant range, and even a small change will cause drastic changes in the molecular structure and chemical function of the body.
The buffer system, respiratory system and kidney compensation system in the body maintain the balance of pH, so that the physiological functions of the body can operate normally and maintain human health. It has been found that the activity of insulin decreases by 30% every time the pH value in blood decreases by 0. 1 unit.
Some people think that diabetes, especially type II diabetes, is not due to less insulin secretion, but to decreased insulin activity. Diabetes mellitus is a typical disorder of nutrition metabolism, which is a disorder of carbohydrate, sugar, protein and fat metabolism. These metabolic disorders are more likely to produce acidic metabolites, thus affecting the stability of human blood pH value.
Drinking water with too low hardness for a long time is not good for your health.
1958, the World Health Organization stipulated in the drinking water standard that the pH value should not be lower than 6.5 and not greater than 9.2; 1984 in the first edition of the drinking water guide, the pH value is set to 6.5 ~ 8.5. In the third edition of Guide to Drinking Water in 2003, the pH value was set at 6.5 ~ 8.0. In the third revision in 2006, the pH value was set at 6.5~9.5. In the hygienic standard of drinking water in China, the pH value of water is set at 6.5~8.5. In human evolution, from drinking natural water and well water to drinking tap water for nearly 100 years, the pH value is 6.5~8.5. Although the human body has strong pH buffering and adjusting ability, it is scientific to keep the pH value of drinking water within a certain range, and the closer the pH value of water is to the pH value of blood, the better.
Many biomedical and epidemiological investigations at home and abroad show that drinking low-hardness water for a long time has a negative impact on human physiological functions. Especially the content of magnesium and calcium in water can effectively prevent the risk of sudden death of cardiovascular and cerebrovascular diseases. When cooking food, using water with too low hardness will lead to the loss of mineral elements in food.
From a large number of epidemiological research reports, it can be seen that the hardness in water is negatively correlated with the incidence of cardiovascular diseases, that is, the lower the hardness and pH value of drinking water, the higher the incidence. Many areas in southern China belong to soft water areas, and the mineral content in water is low, and the pH value is generally around 7.0 or below. With the aggravation of pollution in some areas, especially in the Yangtze River Delta and Pearl River Delta, which belong to acid rain areas, drinking water mainly comes from surface precipitation, so the pH value of drinking water is lower than normal. In recent decades, the pH value of water quality in these areas has declined.
Dr. Zhou said that according to the current quality of bottled drinking water, we found that the pH value of all drinking water containing natural balanced minerals and trace elements was weakly alkaline or very close to 7. However, the pH value of drinking water without minerals or artificially added minerals is often acidic.
Drinking mineral water is processed water.
Is the popular mineral water on the market high-quality healthy drinking water? Is it natural drinking water? Dr. Zhou Li said that the first thing to understand is the characteristics of mineral water. The processing of mineral water is to add minerals on the basis of pure water. Can we solve the problem of pure water by adding artificial minerals? The fact is not as simple as imagined.
Artificial mineral water containing potassium ions, magnesium ions, chloride ions and sulfate ions will make the water more acidic and the pH value may even be lower than 6.0. Moreover, the proportion and composition of artificially added minerals are far less stable than natural sources. The final result is that the normal supplement of trace mineral elements needed by human body cannot be guaranteed, and the natural balance of acid and alkali in human body is affected because of the low pH value.
In addition, due to the different compounds added to water by various manufacturers, it has brought certain difficulties to the national product quality supervision. One thing is certain, the quality of water with minerals is far less than that of high-quality drinking natural water (including natural mineral water). When adding minerals, the mutual balance and antagonism of various anions and cations should be properly considered, otherwise it will not only bring health to people, but also cause some nutritional and health problems.