So If you distill your own water or buy certain types of distilled water like just “steam distilled” the end product is very pure water. (Some brands add stuff back in after the process usually branded as re-mineralized) So it has no minerals in it. Drinking large quantities of pure distilled water without adding some sort of electrolytes back will in theory pull those healthy minerals out of your body. Think of it as a magnet for all the stuff that got pulled out of it when it was distilled.

It’s not unsafe per say you just need to be aware of it and if you choose to do it yourself or buy it without minerals I would recommend buying some sort of electrolytes to add to it. I personally use LMNT flavored salt packets most days, or Keto Chow (not flavored) off Amazon