Scientific health care. Two weeks ago (20 18-3- 12), Professor Lin Qingshun sent a letter signed by Winnie, asking two questions, one of which was whether "hard water" would lead to kidney calculi. Since her email was written in English, I won't copy it, and I will directly relay its main points as follows. Winnie said that she lives in Canada, and locals usually drink tap water or filtered water directly, but they don't boil the water. Her parents don't take this seriously, because they think that tap water is "hard water" (containing minerals), which will cause kidney calculi, and boiling water can remove minerals. Winnie asked herself at the end of the email, "But don't we just need minerals?" Ha ha ha, good question. People are really strange. It is said that eating calcium tablets and magnesium tablets all day is important for this and beneficial for that. However, the same person tried everything and even spent a lot of money to remove calcium and magnesium from drinking water. The reason for this absurd and contradictory phenomenon is actually very simple, that is, it is misled by wrong information. Let's see if boiling water can really remove minerals. The minerals in tap water are mainly calcium and magnesium. The higher the content, the harder the water is. The "hardness" of tap water varies from region to region, but it is usually about medium hardness (100ppm). Calcium and magnesium in water mainly exist in the form of calcium bicarbonate and magnesium bicarbonate, and boiled water can turn them into precipitates of calcium carbonate and magnesium carbonate. Through these sediments? After that, the water was softened. However, calcium and magnesium in water also exist in the form of calcium chloride, calcium sulfate, magnesium chloride and magnesium sulfate, which cannot be removed by boiling. So boiling water can only remove some minerals. Again, let's see if hard water really causes kidney calculi. Dr Marshall Stahle, my colleague in the urology department at the University of California, is an authority on kidney calculi. In 2002, his team published a research paper entitled "Calcium kidney calculi: Effect of Water Hardness on Urine Electrodes" (Calcium kidney calculi: Effect of Water Hardness on Urine Electrolytes). The data of 4833 patients with calcium kidney calculi in the United States were collected, including the hardness of water in their living areas and the frequency of calcium kidney calculi. In this way, people living in the "softest" area will form an average of 3.4 calcium kidney calculi, while people living in the "hardest" area will form an average of 3.0 calcium kidney calculi. In other words, people who drink the "hardest water" are not more likely to get calcium and kidney calculi than those who drink the "softest water". Dr Marshall Stahle published another paper on 20 12. The topic is the influence of calcium intake and intentional calcium absorption on kidney calculi of elderly women: the study of osteoporotic fracture (the influence of calcium intake and intestinal calcium absorption on kidney calculi: the study of osteoporotic fracture). It is found that increasing dietary calcium intake can reduce the incidence of kidney calculi by 45% to 54%. In other words, if you remove calcium from the water, it may increase the risk of kidney calculi's illness. This statement is not alarmist. Please see the document of Canadian Urology Association: (link). Also, please look at the documents of two American cities: (link 1) and (link 2) in short. Whether it is boiled or not has nothing to do with kidney calculi. Note: Calcium oxalate is the most common one in kidney calculi. Some calcium taken from the diet will be absorbed into the blood circulation system. The unabsorbed part will combine with oxalic acid to form calcium oxalate, which will be excreted with feces, reducing the probability of calcium oxalate formation in urethra. About the author: Scientific health care, hosted by Lin Qingshun, a professor (now retired) at the University of California, San Francisco. He has 40 years of medical research experience, published nearly 200 research papers, and served as a member of the jury of more than 60 world-renowned medical journals. From the perspective of medical research, articles based on scientific evidence are published to solve the health myth wandering on the internet, help readers avoid being misled by unconfirmed information, and thus safeguard personal health.