People pay more attention to drinking water than any food: some people say that "hard water leads to kidney stones", and others believe that "pure water is harmful to health without minerals"... What is the relationship between the hardness of water, minerals and health?
The hardness of water is determined by the content of calcium and magnesium in it. The commonly used hardness index is how many milligrams of calcium oxide and magnesium are contained in each liter of water. For example, the national standard for tap water is that the total hardness does not exceed 450 mg. If all of it comes from calcium, it is roughly equivalent to 180 mg of calcium in one liter. What is the impact of extra calcium and magnesium intake on health after drinking such water for a long time?
Calcium and magnesium are essential trace elements for human body, and many people cannot reach the recommended intake in their diet. That is to say, taking into account calcium and magnesium in water can actually help meet human needs. Taking too much calcium does bring health risks, and kidney stones are one of them. But this "too much" is not easy to achieve - the general recommendation is that no more than 2500 mg of calcium per day can be considered safe. For Chinese people who do not consume dairy products generally, it is difficult to reach the "recommended calcium intake" of 1000 mg per day. On this basis, even if you drink two liters of water with the "maximum allowable hardness" every day, the additional calcium intake will not exceed 360 mg, which is quite far from "calcium exceeding the standard".
In addition to calcium and magnesium, there are other minerals in the water. Since minerals are needed by the human body, is "pure water" or "soft water" without minerals harmful to health? We need to note that the nutrients of the human body come from all the diets we eat and drink, and water is only one part of them. Even "very hard" water contains two or three hundred milligrams of calcium per liter. After the water is boiled, a considerable part of these calcium and magnesium ions will become "scale", and the content of water will be lower. Researchers have conducted field surveys in Israel and other places. After residents switched from drinking tap water with high hardness to drinking purified water with almost no minerals, the change of calcium and magnesium content in residents' blood was minimal.
It is also said that pure water "will dissolve and discharge all trace elements in the body" because it does not contain trace elements. This is actually a hypothetical inference. Trace elements in the human body are distributed in their organs and tissues. After pure water is absorbed into the blood, it will no longer be "pure". Finally, the trace elements needed will be left after the filtration of the kidney to be excreted as urine. How can trace elements be "dissolved and excreted" after drinking pure water. In fact, the popularity of pure water in developed countries and regions is very high. In the Middle East, people drink almost all pure water. For decades, the incidence of calcium deficiency and kidney injury has not increased.
The human body's demand for minerals mainly depends on various foods. However, the hardness of water, or various minerals in it, will affect the taste and performance of water. Whether water is "good to drink" depends on the minerals and other "impurities" in it. When the water with high hardness is boiled, a large amount of white sediment will appear, which will not affect the health, but will affect the appearance and taste. In short, as long as other indicators are qualified, whether water is hard or soft has no impact on health. ▲
(Editor in charge: Guo Yu, Guan Fei)
