What is Demineralized Water?
Demineralized water is any water that has been treated to remove most or all of its mineral salts through processes like deionization, reverse osmosis, or distillation. It is not the same as standard purified water, which may have some minerals added back in for taste and health benefits. The term is often used interchangeably with deionized (DI) water, which specifically removes mineral ions, or distilled water, which removes a broader range of impurities through boiling and condensing. Demineralized water is typically used in industrial, laboratory, and automotive applications where mineral buildup and corrosion are problematic.
How Demineralization Works
Several methods are used to create demineralized water:
- Deionization (DI): This process uses electrically charged resins to attract and bind to mineral ions (cations like calcium and magnesium, and anions like chloride), effectively pulling them out of the water. This method is very effective at removing mineral salts but does not remove uncharged contaminants such as bacteria or viruses.
- Distillation: Water is boiled, and the resulting steam is captured and condensed back into a liquid state. This process leaves behind dissolved solids, including minerals and salts, but may not be as effective at removing volatile organic compounds (VOCs) with low boiling points.
- Reverse Osmosis (RO): Water is forced through a semi-permeable membrane that blocks most dissolved solids and contaminants. While RO is highly effective at removing impurities, it also strips away beneficial minerals, resulting in demineralized water unless a remineralization step is included.
The Health Implications of Drinking Demineralized Water
While a single glass of demineralized water is unlikely to cause harm, long-term or exclusive consumption can pose significant health risks. A 2005 WHO report, and subsequent confirmations, highlighted that demineralized water without mineral enrichment is not ideal for drinking and can compromise the body’s mineral and water metabolism.
Mineral Deficiencies and Leaching
One of the most concerning health risks is the potential for mineral deficiencies. Essential minerals like calcium and magnesium are often removed during the demineralization process. While the primary source of these minerals is food, the minerals absorbed from water can play a protective role. Prolonged consumption of mineral-deficient water means the body receives no supplementary intake from this source, which can be particularly detrimental for those with already marginal diets. Additionally, demineralized water is often described as “hungry” or “aggressive” because it lacks dissolved minerals and will actively try to absorb them from its surroundings. When consumed, this can cause it to leach minerals from the body’s tissues during digestion.
Electrolyte Imbalance
The consumption of demineralized water can lead to an electrolyte imbalance. Electrolytes such as sodium, potassium, calcium, and magnesium are vital for nerve function, muscle contraction, and maintaining fluid balance. Drinking large amounts of mineral-free water can dilute the body’s electrolyte concentration, a condition that can result in symptoms ranging from fatigue and headache to more severe issues like cardiac irregularities. In extreme cases, this can lead to water intoxication (hyponatremia), especially for those engaged in intense physical activities.
Adverse Effects on Cooking
Using demineralized water for cooking can further exacerbate mineral deficiencies. Studies cited in the WHO report show that cooking food in low-mineral water causes a significant loss of essential elements from vegetables, meat, and cereals, sometimes by as much as 60% for calcium and magnesium. In contrast, using hard water can actually reduce mineral loss from food.
Comparison of Water Types
| Feature | Demineralized Water (via DI) | Distilled Water | Purified Water (often RO with Remineralization) |
|---|---|---|---|
| How It's Made | Ion exchange resins remove charged mineral ions. | Boiling and condensing water vapor to separate it from solids. | Multiple filtration stages (including RO) followed by adding back minerals. |
| Removes Minerals | Yes, effectively removes mineral salts. | Yes, removes all dissolved minerals and salts. | Initially removes minerals, but adds beneficial ones back. |
| Removes Bacteria/Viruses | No, does not remove non-ionic contaminants. | Yes, effectively removes most microbes and pathogens. | Yes, effectively removes microbes and pathogens. |
| Taste | Flat or insipid due to lack of minerals. | Very flat, can be unappealing. | Typically clean, fresh, and pleasant. |
| Best For | Industrial, lab, and automotive uses. | C-PAP machines, steam irons, and specific medical purposes. | Everyday drinking and cooking. |
Is Occasional Consumption Safe?
For most healthy adults, drinking demineralized water occasionally is not a significant health risk, as long as it isn't the sole source of hydration. The body's mineral stores are primarily replenished through a balanced diet, and the kidneys can effectively regulate electrolyte levels. The real danger arises with exclusive, long-term reliance on mineral-deficient water. For infants, pregnant women, or individuals with pre-existing health conditions, exclusive consumption should be avoided.
The Role of Remineralization
Many water treatment systems that produce demineralized water for residential use, particularly reverse osmosis systems, now include a remineralization stage. This step adds a balanced mix of beneficial minerals like calcium and magnesium back into the water after purification. Remineralizing the water improves its taste and restores some of the health benefits associated with drinking mineralized water. For those with home RO systems, installing a remineralization filter is a practical way to ensure clean, healthy, and great-tasting water for daily use.
Conclusion: Navigating Your Water Choices
While demineralized water is a crucial resource for many industrial and medical applications, it is not the optimal choice for regular human consumption. Long-term use without mineral supplementation can lead to deficiencies and electrolyte imbalances, as evidenced by numerous health studies, including those by the WHO. For daily hydration, it is far safer and more beneficial to choose water that contains essential minerals. Tap water, bottled mineral water, or purified water from a remineralizing reverse osmosis system are all superior choices for maintaining your overall health and well-being. Always consider your water source and processing methods to make the best choice for your body. For more information on the safety of demineralized water, you can reference the World Health Organization's report on nutrients in drinking water.
