What is Deionized Water?
Deionized (DI) water, or demineralized water, is water that has undergone a purification process called ion exchange to remove all dissolved mineral ions. In this process, water is passed through electrically charged resin beads. These resins attract and 'exchange' mineral ions, such as calcium, sodium, and magnesium, with hydrogen ($H^+$) and hydroxyl ($OH^-$) ions. The hydrogen and hydroxyl ions then combine to form pure water ($H_2O$), leaving the mineral ions behind. This level of purity makes DI water invaluable for specific industrial and laboratory applications where mineral contamination could interfere with results or cause machinery damage, but it also creates significant health hazards if consumed.
Health Risks of Consuming Deionized Water
Mineral Leaching from the Body
One of the most immediate concerns with drinking DI water is its powerful solvent properties. Often referred to as "hungry" water, deionized water actively seeks to absorb ions from its environment to regain equilibrium. When consumed, this aggressive solvent can leach essential minerals directly from your body's tissues, including those in your gut and bloodstream. This can cause significant mineral imbalances and deficiencies over time, as the body attempts to correct the osmotic pressure differences. The World Health Organization (WHO) has noted that drinking water low in minerals is associated with health issues related to compromised mineral homeostasis.
Increased Risk of Contamination
Unlike distillation, the deionization process does not remove uncharged organic compounds, viruses, or bacteria. While DI water systems are often used with other pre-filtration methods like reverse osmosis to remove these contaminants, the final DI product itself is not sterile. This means that if DI water is produced from an untreated or poorly treated source, or becomes contaminated after processing, it can still harbor dangerous pathogens that pose a health risk. The absence of any disinfectant residual also allows for potential bacterial regrowth in the storage and distribution systems, further increasing the risk.
Corrosive Nature and Toxicity
DI water's highly reactive and corrosive nature can also be a source of danger. Because it is free of minerals, it will attack and leach metals from the piping and storage containers it comes into contact with. This can introduce toxic metals like lead or copper into the water, which are then consumed. The WHO has reported on the potential for increased dietary intake of toxic metals due to the corrosive activity of demineralized water.
Affects Taste and Thirst Quenching Ability
Water's taste comes from its dissolved minerals. The complete removal of these minerals leaves deionized water with a distinctively flat or bland taste that many find unappealing. This can lead to a reduced intake of fluids, risking dehydration. Furthermore, without the electrolytes typically found in mineralized water, DI water is less effective at quenching thirst and replenishing electrolytes lost through sweat. This can be particularly problematic for athletes or individuals in hot climates.
Inadequate for Cooking
Cooking with DI water can also have detrimental effects on health. Studies have shown that when food is cooked in demineralized water, it can lead to a substantial loss of essential elements from the food itself, with losses up to 60% for magnesium and calcium. This reduces the overall nutritional value of the meal and can contribute to mineral deficiencies, especially if one's diet is already borderline sufficient in these nutrients.
Deionized Water vs. Distilled Water vs. Tap Water
To better understand why DI water is not for drinking, let's compare its properties to two other common types of water.
| Feature | Deionized (DI) Water | Distilled Water | Tap Water |
|---|---|---|---|
| Purification Method | Ion exchange resins remove mineral ions. | Boiling and condensation remove minerals, viruses, and bacteria. | Treated at a municipal plant, may contain residual minerals and disinfectants. |
| Mineral Content | Almost zero, as mineral ions are deliberately removed. | Almost zero, as minerals are left behind during boiling. | Varies greatly by source, contains essential minerals like calcium and magnesium. |
| Pathogen Removal | Does not remove uncharged pathogens like viruses and bacteria. | High level of removal through boiling and condensation. | Disinfected, but can be prone to recontamination in pipes. |
| Corrosiveness | Highly corrosive due to lack of mineral ions. | Somewhat corrosive due to lack of minerals. | Neutral or slightly alkaline, less corrosive due to mineral content. |
| Suitability for Drinking | Not recommended for regular consumption due to health risks. | Acceptable for occasional use, but lacks minerals. | Ideal and safe for regular consumption, provides minerals. |
Appropriate Uses of Deionized Water
While not suitable for drinking, deionized water has a wide range of important uses where its low mineral content is a benefit rather than a drawback. These include:
- Laboratory Applications: Used in experiments, to prepare solutions, and to clean glassware to prevent mineral interference.
- Medical and Pharmaceutical Manufacturing: Used in the production of pharmaceuticals, cosmetics, and for sterilizing medical equipment.
- Industrial Processes: Employed in power plants, cooling systems, and manufacturing to prevent mineral scale buildup.
- Automotive Care: Used in car batteries and engine cooling systems to avoid corrosion.
Conclusion
In summary, while deionized water is an excellent solvent and a vital component in many industrial and scientific applications, its unique chemical properties make it dangerous for regular human consumption. The process of ion exchange, while effective at removing mineral ions, leaves the water aggressive and potentially contaminated with pathogens. Risks include mineral leaching from the body, corrosiveness that can introduce toxic metals, poor taste that deters hydration, and the potential for residual contaminants. For safe and healthy drinking, stick to tap water or properly filtered drinking water that retains essential minerals. The dangers associated with consuming deionized water far outweigh any perceived benefit of its purity, making it a critical health consideration to avoid.
Safe Alternatives to Deionized Water
For those seeking purer alternatives to tap water for drinking, several safer options exist:
- Filtered Tap Water: Using a high-quality home water filtration system can remove harmful contaminants while retaining beneficial minerals.
- Bottled Mineral Water: Provides hydration along with a supply of natural, essential minerals.
- Reverse Osmosis (RO) Systems: RO systems effectively remove a broad range of impurities. Some systems even include remineralization filters to add healthy minerals back into the water for improved health and taste.
By understanding why can't we drink deionized water, consumers can make informed choices to protect their health and ensure they get the right kind of hydration. For further research on the health risks of demineralized water, consult the World Health Organization's report on drinking demineralised water.
