It’s true that RO units remove some minerals but that isn’t really the whole story. The mineral issue is probably the most controversial question in drinking water purification. “Experts” on both sides of the issue speak convincingly.
Minerals in water are inorganic and hard for your body to use. You get most of your minerals from food, which provides organic, easily assimilated minerals. The human body is a sophisticated instrument capable of adapting to a wide range of circumstances and capable of thriving in areas having water of high or low mineral content.
As long as water is palatable, it’s within the body’s acceptable range. However, your drinking water should contain minerals (unlike distilled which has none), otherwise nutrients in your body can be lost through your body’s waste disposal system. The main issue with water is chemicals, not minerals. Whether water contains 30 or 3 parts per million calcium isn’t really significant, but the difference between 0.5 and 5 parts per million chloroform is of life or death importance