北京市送水公司

纯净水是否有害健康，不仅在公众中间，在专业人士之间也有许多争议。跟自来水相比，纯净水滤掉了矿物质离子。争论的焦点就在于：纯净水缺少的矿物质离子，对健康到底有多大影响？

Whether pure water is harmful to health is also controversial not only among the public, but also between professionals. Compared with tap water, pure water filters out mineral ions. The focus of debate is: what are the effects of mineral ions that are lacking in pure water?

多数人认为没有多大影响，因为人体摄入矿物质，还是要靠食物。不过也有不同的声音，世卫组织就比较反对纯净水，镁对于心脏健康很重要，他们认为饮用水中镁含量不应低于10毫克每升，而纯净水中镁含量太低。

Most people do not think much of it because human intake of minerals depends on food. But there are different voices. The World Health Organization is more opposed to pure water. Magnesium is important for heart health. They think the content of magnesium in drinking water should not be less than 10 milligrams per liter, and the content of magnesium in pure water is too low.

以色列缺乏淡水，所以很多生活用水是从海水净化而来。海水除去了盐，自然也就去掉了钙镁离子。所以以色列学术界对于水中的镁做了许多研究。2017年4月出版的《水与健康杂志》（Journal of Water and Health）发表了一项研究，探讨了以色列居民饮用净化海水对血镁浓度的影响。

Israel is short of fresh water, so a lot of domestic water is purified from seawater. Seawater removes salt and naturally removes calcium and magnesium ions. So the academia in Israel has done a lot of research on magnesium in water. A study published in the April 2017 issue of the Journal of Water and Health published a study of the effects of drinking water purification by Israeli residents on the concentration of magnesium in blood.

这项研究是数据分析。在以色列，有15个地区在2013年引入了脱盐海水作为主要的生活用水，另外还有24个地区没有引入。根据公开的检测结果，引入脱盐海水之前，饮用水的平均镁含量是25.1毫克/升；引入脱盐海水之后，平均镁含量是5.4毫克/升。作者从医疗机构获得了这些地区的居民在2010年到2016年间的的血镁浓度数据，通过统计分析得出饮用脱盐海水对血镁含量的影响。

The study is data analysis. In Israel, 15 areas introduced desalination seawater as the main domestic water in 2013, and 24 other areas were not introduced. The average magnesium content of the drinking water was 25.1 mg / L before the desalination was introduced, and the average magnesium content was 5.4 mg / L after the desalination of seawater was introduced. The author obtained the blood magnesium concentration data from 2010 to 2016 from the medical institutions, and the effects of the desalted seawater on the content of magnesium in the blood were analyzed by statistical analysis.

研究一共获得了66754人的数据。在2010到2013年之间，那15个地区居民的血镁平均含量是2.0650.19毫克/升；2013年引入脱盐海水作为主要饮用水，之后2014到2016年间的血镁平均含量为2.0570.19毫克/升。平均含量下降了0.008毫克/升，下降幅度0.39%，其实还在波动范围内。不过因为样本数很大，这个下降幅度具有统计学上的显著性。此外，医学上把1.7-2.4毫克/升的血镁浓度作为正常范围，“1.6毫克/升”作为低血镁的判断标准。在这15个地区，2010到2013年之间的低血镁率为1.62%，而引入脱盐海水之后的2014到2016年间，低血镁率升高到了1.91%。这两个数字之间，也具有统计学上的显著性。所以作者认为：脱盐海水的引入降低了人们的镁摄入量，而这个“降低”具有临床意义，也就是说，会影响到公众健康。

The study obtained a total of 66754 people. Between 2010 and 2013, the average blood magnesium content in those 15 areas was 2.0650.19 mg / L; in 2013, the desalted sea water was introduced as the main drinking water, and the average blood magnesium content was 2.0570.19 mg / L between 2014 and 2016. The average content dropped by 0.008 mg / liter, a decrease of 0.39%, which is still fluctuating. However, because the sample size is large, the decrease is statistically significant. In addition, the blood magnesium concentration of 1.7-2.4 mg / l was taken as the normal range in medicine, and the "1.6 mg / L" was used as the criterion of low blood magnesium level. In these 15 regions, the low blood magnesium ratio between 2010 and 2013 was 1.62%, and the low magnesium rate rose to 1.91% between 2014 and 2016 after the introduction of desalted seawater. The two figures also have statistical significance. So the author believes that the introduction of desalted sea water reduces the intake of magnesium in people, and this "decrease" is of clinical significance, that is to say, it will affect public health.

不过从另一个角度来看，平均血镁含量从2.065毫克/升降低到2.057毫克/升，降低的幅度并不大。实际上，在另外那24个没有引入脱盐海水的地区，2010到2013年间的血镁浓度平均值是2.056毫克/升，跟那15个喝脱盐海水的地区相当；2014-2016年间，血镁浓度平均值却又增加到了2.063毫克/升，似乎可以理解为这个幅度的变化算是正常的波动。更重要的是，在这些一直喝常规自来水的地区，2010到2013年间的低血镁率为2.18%，2014到2016年间为1.98%，都比那15个地区喝脱盐海水之后的低血镁率要高。

But from another perspective, the average blood magnesium level from 2.065 mg / down to 2.057 mg / liter does not decrease significantly. In fact, in the other 24 areas without salt desalination, the average concentration of blood magnesium between 2010 and 2013 was 2.056 mg / L, equivalent to that of those 15 desalinated waters; the average concentration of blood magnesium increased to 2.063 mg / L in the 2014-2016 years, which seems to be understood to be a positive change. Frequent fluctuations. More importantly, from 2010 to 2013, the low blood magnesium rate was 2.18% and 1.98% from 2014 to 2016, which was higher in lower blood magnesium rates after drinking desalinated seawater from those 15 regions.

作者是从统计学的角度来评判，认为脱盐海水的引入“降低”了血镁含量，增加了低血镁率。但如果从两类地区的对比来看，那15个地区喝脱盐海水之后，血镁平均浓度跟对比的那24个地区相当，而低血镁率还要低一些。更重要的是，作者在讨论中也提到，普通人群中的低血镁率在2.5%到15%之间。也就是说，以色列的这些居民，不管是以前喝普通的自来水，还是后来喝矿物质含量很低的脱盐海水，低镁率都还低于其他人群正常范围的下限。分析数据得出的“变化趋势”虽然有统计学上的显著性，但变化幅度非常小，到底是真的有“临床价值”，还是有别的“混在因素”，或者仅仅是“统计假象”，或许需要更多的研究来验证。

Judging from statistics, the author believes that the introduction of desalinated seawater reduces blood magnesium content and increases the rate of low blood magnesium. But if the 15 regions drank the desalination of the sea, the average concentration of blood magnesium was the same as those of the 24 regions in the 24 regions, and the low blood magnesium rate was a little lower. More importantly, the author also mentioned in the discussion that the rate of low blood magnesium in the general population is between 2.5% and 15%. In other words, the low magnesium rates were lower than the normal limits of other populations, whether they were drinking ordinary tap water before, or later drinking water with low mineral content. The "change trend" obtained by the analysis data is statistically significant, but the change is very small. It is really "clinical value", or there are other "mixed factors" or "statistical illusion", which may need more research to verify.

当然，数字是死的，对于数据的解读，却有一定的主观性。这项研究的结果，可以按照作者的解读——“脱盐海水的低矿物质含量降低了人们的血镁浓度”，所以采取行动来修正也没有没什不好。在以色列，也确实有在脱盐海水中添加矿物质的呼声。不过，如果解读成“喝低镁含量的纯净水，对血镁含量没有明显影响”，也没有什么不可以。尤其是对于大多数喝纯净水的中国人民，一般只是“喝”纯净水，做饭做菜的时候通常也还是用自来水，就更不值得纠结了。

Of course, the number is dead, and the interpretation of data is subjective. The results of the study could be interpreted by the author, "the low mineral content of the desalted sea water reduces the concentration of blood and magnesium in people", so it is not bad to take action to correct it. In Israel, there is indeed the voice of adding minerals in desalinated seawater. However, if it is interpreted as "pure water with low magnesium content, there is no obvious effect on blood magnesium content", there is nothing wrong with it. Especially for the majority of the Chinese people who drink pure water, it is usually just "drink" pure water, and usually use tap water when cooking. It is not worth getting entangled.