Yes, Drinking Demineralized Water is Bad for You

There  appears to be a fair amount of controversy on the internet surrounding the safety of drinking demineralized water.  The best information available on this subject that I could find is the World Health Organization’s 2005 Report Nutrients in Drinking Water.

The World Health Organization believes that researchers have tended to focus on studying the toxicological effects of contamination in water, rather than beneficial substances in water, such as calcium and magnesium.

Aesthetically, very pure water is appealing to many people…a fact that water filtration/distillation companies happily exploit.  In fact, our bodies are designed to drink water that has come in contact with earth minerals.  Calcium and magnesium are essential nutrients, and researchers have long observed evidence that drinking naturally soft water is correlated with heart disease.

There several other health concerns associated with drinking demineralized water, including: 1.) osmotic shock to the body’s mucous membranes; 2.) disruption to the body’s mineral homeostasis; 3.) lower consumption of important nutrients like calcium and magnesium; and 4.) consumption of contaminants leaching into the demineralized water from piping/distribution.  Several examples of human and animal studies documenting health effects are presented in the WHO’s report.

In spite of these concerns, extreme filtration, reverse osmosis and distillation will probably have an increasingly important role in water treatment in the future.  Drinking water supplies are increasingly dependent on very poor quality sources, such as brackish/saline water bodies or direct recycling of wastewater.  In distribution systems, minerals must be added back into the water to keep it from dissolving the piping and thus the health impact will be minimized.  But individuals may have to rely on personal reverse osmosis or ultrafiltration systems to remove dangerous contaminants that are not being taken out of the public water supply.

The WHO recommends that countries implement minimum hardness recommendations for drinking water.  The EPA currently provides a maximum water quality standard for hardness but not a minimum.  A non-enforceable standard would probably be helpful for educational purposes at the very least.