Some questions are not easily answered by Google or Wikipedia. About a year ago our department moved into a new building that was equipped with distilled H2O at our sinks. Although it was easily determined that the dH2O in our lab was not fit for drinking (I got sick as a dog upon drinking it), this was a factor of decidedly undistilled water coming out of the distilled tap. Nevertheless, I was curious about whether or not distilled water was safe to drink, or beneficial. I must have looked through ten pages of Google to find an authoritative, definitive answer on this and couldn’t. I mostly found message boards saying one thing or another. It was simply ungooglable.
Anyway, one of my goals here is to make the ungooglable googlable, so I asked a friend and Chemistry PhD about it. First, some background.
Water is an aggressive solvent
The purer the water, the more aggressive it is as a solvent. Leave metal tools in water overnight, and it will probably be ok the next morning. If it is distilled, your tools will show signs of rust within hours. Those that warn about the dangers of DH2O claim that in like fashion it will leech minerals out of your body, leaving you in poor health and at worst mineral deficiencies.
However, because dH2O is so aggressive, it becomes “undistilled” rather quickly. If you leave a glass of dH2O out in the open air, it will soon become slightly acidic by breaking down carbon bonds from the air and producing carbonic acid. So any concerns about dH2O leeching out minerals can be solved by simply leaving the water out. High end water filtration systems for domestic use often run dH2O back through a bed of rocks so the water picks up minerals naturally before passing through your GI.
That being said, is there really harm in drinking dH2O straight out of the tap. Provided it is really distilled, my Chemistry PhD friend says there isn’t too much harm in it. Once the water hits your mouth it’s bombarded with organic molecules, and your stomach is very acidic and won’t contain the minerals that would leech out anyway. The only concern is that tap water provides minerals that are otherwise hard to get and you’d have to supplement. I estimate you could probably get away with drinkin 80% of your water dH2O with no problems.
The bigger question is whether dH2O is safe for making coffee. By all accounts it’s perfectly fine, because it is no longer distilled as it passes through the beans. One question I posed to my chemistry friends is whether the aggressive solvency of dH2O would extract more flavor and/or caffeine from the beans. My PhD friend said that caffeine is an alkaloid and since tap water is slightly acidic it would extract more caffeine. I think an experiment should be conducted to verify this.