What Is Deionized Water?
Deionized (DI) water is created through a chemical process that uses ion exchange resins to remove dissolved mineral ions, such as calcium, magnesium, iron, and sodium. In this process, water flows through charged resin beads that attract oppositely charged ions, effectively exchanging them for hydrogen (H+) and hydroxide (OH-) ions, which combine to form pure H₂O. While this method is highly effective at removing mineral salts, it does not remove uncharged contaminants like many viruses and bacteria. This is why DI water is typically used for industrial, laboratory, and manufacturing purposes where ultra-pure water is critical for processes like rinsing electronics, preparing chemical solutions, and sterilizing medical equipment.
Why You Shouldn't Drink Deionized Water Regularly
Despite its technical purity, drinking deionized water as your primary source of hydration is widely discouraged by health experts for several important reasons.
The "Hungry" Water Effect
Because deionized water is stripped of its mineral content, it is chemically unstable and highly aggressive. It is often referred to as "hungry" water because it actively seeks to re-balance itself by absorbing ions from anything it comes into contact with. When consumed, this can cause it to leach minerals from your body and the containers it is stored in.
Mineral Depletion from Your Body
One of the most significant risks of drinking deionized water is the loss of essential minerals. While dietary sources are the main providers of minerals, water also plays a crucial supplementary role. Long-term consumption of DI water, which is devoid of minerals like calcium and magnesium, can contribute to mineral deficiencies and disrupt the body's natural balance. The World Health Organization (WHO) has noted a negative effect on human homeostasis mechanisms from consuming low-mineral water.
Potential Contaminant Risk
Unlike distillation, which uses boiling and condensation to kill or remove pathogens, the deionization process does not reliably eliminate uncharged microorganisms such as bacteria and viruses. This means that DI water is not necessarily sterile and could pose a health risk if its source water was not pre-filtered or disinfected.
Leaching of Toxic Metals
Due to its corrosive nature, deionized water can leach trace amounts of toxic metals from storage containers and distribution pipes. This is a particular concern if DI water is stored in plastic containers made with monomers, or distributed through old plumbing. While regular tap water contains minerals that help prevent this leaching, the high purity of DI water intensifies the effect.
Comparing Deionized, Distilled, and Tap Water
Understanding the differences between types of water is key to choosing the right one for your needs. Here is a comparison of deionized, distilled, and tap water.
| Feature | Deionized Water | Distilled Water | Tap Water (Filtered) |
|---|---|---|---|
| Purification Method | Ion exchange using resins | Boiling and condensing steam | Multi-stage filtration (e.g., carbon, reverse osmosis) |
| Mineral Content | Virtually none (ions removed) | None (minerals left behind) | Retains some minerals, dependent on filter type |
| Contaminants Removed | Mineral ions | Dissolved solids, bacteria, viruses | Most contaminants, but varies by system |
| Pathogen Risk | Can contain uncharged viruses/bacteria | Sterile (pathogens are killed/removed) | Dependent on filter; requires disinfection |
| Taste | Flat or bland | Flat or insipid | Varies, often preferred over purified water |
| Safety for Drinking | Not recommended for daily consumption | Safe to drink, but lacks beneficial minerals | Safe, with balanced minerals after filtration |
| Common Uses | Labs, industrial processes, electronics manufacturing | Medical equipment, humidifiers, batteries | Everyday drinking, cooking, bathing |
Health Implications of Drinking Low-Mineral Water
Research has explored the health effects of demineralized water on human physiology and function. Here are some key findings:
- Electrolyte Imbalance: Consuming low-mineral water can negatively affect the body's mineral homeostasis. Studies have shown increased diuresis and altered excretion of sodium, potassium, chloride, calcium, and magnesium. This imbalance can compromise the function of vital organs and lead to symptoms like tiredness, weakness, and headaches.
- Cardiovascular Health: Epidemiological studies spanning decades have consistently found a correlation between soft water (low in calcium and magnesium) and an increased risk of cardiovascular disease morbidity and mortality. The minerals in water, particularly magnesium, appear to offer a protective effect.
- Other Health Effects: A 2020 report noted potential links between drinking low-mineral water and an increased risk of specific health issues, including hypertension, certain neurological disorders, and bone demineralization. For infants, preparing drinks with distilled or demineralized water without mineral supplementation has been associated with metabolic issues.
A Better Alternative for Drinking Water
For healthy and safe hydration, alternatives to deionized water are readily available and more suitable for human consumption. While DI water serves critical industrial functions, a home water filtration system is a far superior choice for daily drinking.
Consider these options:
- Reverse Osmosis (RO) with Remineralization: An RO system is highly effective at removing a broad range of contaminants, similar to DI water, but a post-filter can reintroduce healthy minerals for better taste and nutritional value.
- High-Quality Filtered Tap Water: Filtering your tap water removes common contaminants while retaining a healthy mineral balance. Options include pitcher filters, under-sink filters, and whole-house systems.
Conclusion: The Bottom Line on DI Water
While a single, incidental glass of deionized water won't harm you, it should not be consumed as a regular source of hydration. The process that makes it valuable for industrial and laboratory use—removing all mineral ions—is what makes it unsuitable for daily drinking. Its lack of essential minerals can lead to health imbalances, it poses a risk of consuming pathogens and leached metals, and its aggressive, flat taste can be unpleasant. For a safe and refreshing drinking experience, stick to filtered tap water, quality bottled water, or a home water filtration system that retains healthy minerals.
For more detailed information on the health risks associated with demineralized water, consult the World Health Organization's report, "Health risks from drinking demineralised water".
