Water can contain clinically relevant quantities of minerals, but as the article you linked states it is secondary to food. Some regions have naturally very sof

Water can contain clinically relevant quantities of minerals, but as the article you linked states it is secondary to food. Some regions have naturally very soft waters (famously Pilsen, Czech Republic, where it is an important part of Pilsener beer). Those waters don't have clinically relevant mineral content, but people there don't have mineral deficiencies unless their diet is also mineral deficient. I've heard your claim that drinking ultra-pure water is dangerous many times before, but I've never seen any citation from a reputable journal. It seems highly implausible to me, as the ultra-pure water will cease to be ultra-pure immediately as it hits your stomach. In general it's very difficult to keep ultra-pure water pure.