What is Demineralized Water?
Demineralized water, often referred to as deionized water, is water that has been treated to remove most or all of its mineral salts and ions. The removal of these charged mineral particles results in water with very low electrical conductivity, making it highly pure for technical applications.
There are several processes to achieve demineralization, with the most common being:
- Reverse Osmosis (RO): This process forces water through a semipermeable membrane, filtering out dissolved solids, salts, and many other contaminants. Many modern home water filters use this technology.
- Ion Exchange: Water is passed through resin beads that exchange mineral ions (e.g., calcium, magnesium) for hydrogen (H+) and hydroxide (OH-) ions, which then combine to form pure water. This method does not remove uncharged contaminants like bacteria or viruses.
- Distillation: Water is boiled, and the resulting steam is collected and condensed back into liquid, leaving behind minerals and many impurities. This is an energy-intensive process.
The Health Risks of Drinking Demineralized Water
While demineralized water is not immediately dangerous, health organizations and researchers have outlined potential risks associated with its long-term consumption. The core issue is the absence of vital minerals, particularly calcium and magnesium, which play a crucial role in bodily functions.
Mineral Deficiency: Water is a supplementary source of dietary minerals. For individuals with a borderline or low intake of essential minerals from food, relying solely on demineralized water can worsen the deficit. The body can absorb minerals from water more readily than from some foods, making this water source significant. Prolonged deficiencies can lead to:
- Cardiovascular Issues: Studies have linked the consumption of water low in magnesium and calcium to increased risks of cardiovascular disease and higher blood pressure.
- Bone Health Concerns: A lack of dietary calcium, exacerbated by low-mineral water, is associated with a higher risk of fractures and osteoporosis, particularly in children and older adults.
- Electrolyte Imbalance: Especially relevant for athletes or during high-intensity activity, consuming large volumes of mineral-free water can alter the body's water-salt balance, leading to electrolyte disturbances and associated symptoms like headaches, weakness, and cramps.
Potential for Contamination and Leaching: Demineralization, especially through ion exchange, does not remove all contaminants. Unlike distilled water, deionized water may still contain viruses and bacteria. Furthermore, demineralized water is highly aggressive and seeks to absorb minerals from any substance it touches. This means it can leach metals from plumbing systems and containers, potentially increasing the intake of toxic elements.
Industrial Use vs. Domestic Consumption
Demineralized water is a crucial component in various industries precisely because of its lack of mineral content, which would otherwise cause problems like scaling and corrosion.
- Industrial: It is used extensively in manufacturing, electronics, pharmaceuticals, and power generation to protect equipment and ensure product quality. For example, in steam boilers, it prevents mineral buildup that can lead to failure.
- Domestic: The low mineral content makes it excellent for household appliances like steam irons and humidifiers, as it prevents mineral scale buildup. However, this is not a recommendation for daily consumption. The removal of minerals alters the water's taste, often described as 'flat' or 'off', which some people find unappealing.
Cooking with Demineralized Water
Using demineralized water for cooking can also negatively impact your diet. Studies have shown that boiling food, particularly vegetables, in low-mineral water can cause significant losses of essential minerals, which are drawn out into the cooking water and then discarded. In contrast, using mineralized water retains more nutrients in the food.
How to Mitigate the Risks
For those who use RO systems at home, there are ways to enjoy the benefits of purified water while avoiding the risks of mineral deficiency. Many modern RO systems now come with a final remineralization stage that adds beneficial minerals like calcium and magnesium back into the water. Alternatively, you can compensate for the lost minerals through a varied, mineral-rich diet. Adding trace mineral drops to your demineralized water can also help.
| Feature | Demineralized Water | Natural Mineral Water | Tap Water |
|---|---|---|---|
| Mineral Content | Very Low to None | Naturally occurring minerals (e.g., calcium, magnesium) | Varies, contains minerals and dissolved solids |
| Purification Method | Ion exchange, RO, distillation | Sourced from underground aquifers; minimal processing | Varies by municipality; filtration, disinfection |
| Taste | Flat or insipid | Refreshing, distinct based on mineral composition | Varies, can taste of chlorine or dissolved solids |
| Primary Use | Industrial, laboratory, appliances | Drinking, hydration | Drinking, cooking, washing |
| Health Impact (Long-Term) | Potential mineral deficiency | Health benefits from natural minerals | Can contain beneficial minerals, but also contaminants |
| Safety | May contain bacteria (DI); risk from leaching | High quality when regulated; potential for contaminants if not tested | Generally safe, but quality can vary greatly |
Conclusion: Navigating Your Water Choice
While it is technically safe to drink demineralized water in the short term, health experts, including the WHO, advise against its prolonged use as a primary drinking source due to the risk of mineral deficiencies. The aggressive nature of demineralized water can also cause it to leach metals from pipes. For everyday hydration, especially if relying on a home RO system, opting for a system with a remineralization stage or ensuring a mineral-rich diet is the best approach. Demineralized water is best reserved for its intended industrial applications, specialized appliances, and specific medical uses where high purity is essential. A balanced perspective acknowledges the need for water purity while respecting the body's need for vital minerals. For more detailed information on the health risks, consult the World Health Organization report on demineralized water.
