Is it healthy to drink pure water？

Drinking 3 to 4 bottles of pure water wont cause big problems， but drinking too much may have negative effects. Drinking water not only quenches thirst， but also， more importantly， to restore the body electrolyte balance and add some minerals needed by the body. On the market， we can see space water and distilled water， which are pure water. It is better to drink less pure water， because it does not contain minerals the body needs. So what can be called mineral water ？ In accordance with national standards on mineral water， if the water meets any one of the following indicators， we call it mineral water： lithium and strontium （0.2 ～ 5 mg/L）， selenium （0.01 ～ 0.05 mg/L）， zinc （0.20mg/L）， silicic acid （25.0 mg/L）， the free CO2 （250 mg/L）， bromine （1.0 mg/L）， iodine （0.20 mg/L）， and salinity （1000mg/L）. Take selenium for example， only when the amount of selenium is between 0.01 ～ 0.05mg/L， it could be called selenium mineral water. When the selenium content is less than 0.01mg/L， it can only be called "spring" rather than mineral water； but if the amount is higher than 0.05mg/L， it is harmful. If the economic condition permits， to drink non-heated mineral water that is with the shelf life is a good thing. But the most convenient and economical choice is to drink clear and transparent boiled water. Other kinds of drinks may contain high amount of sugar， which are not suitable to drink.

（Answered by Zheng Keyan）