What is Demineralized Water?
Demineralized water is simply water that has been treated to remove most, if not all, of its mineral content in a process called demineralization. These minerals, often dissolved as ions like calcium, magnesium, and sodium, are present naturally in most water sources. The goal is to produce high-purity water, typically for industrial, laboratory, or pharmaceutical applications where mineral deposits and conductivity could interfere with sensitive equipment or processes. However, demineralized water is also part of the process for producing certain types of bottled water for human consumption, though often with a final re-mineralization step.
The Different Types of Bottled Water
The key to understanding if your bottled water is demineralized lies in its type. The Food and Drug Administration (FDA) in the U.S. and similar bodies worldwide regulate bottled water, classifying it primarily into three main categories.
Purified Water
This is the category where demineralization is most common. Purified water is often sourced from municipal tap water or groundwater and undergoes a multi-step purification process to remove all impurities. This process can include reverse osmosis, distillation, or deionization, which strip the water of its mineral content along with contaminants. Following purification, manufacturers typically add a small, controlled amount of minerals back into the water for taste and a smooth finish, as un-remineralized demineralized water can taste flat.
Spring Water
Spring water is sourced directly from an underground formation from which water flows to the surface naturally. As it travels through layers of rock, it picks up trace minerals and electrolytes. The bottling process for spring water focuses on removing heavy particles and unwanted elements without altering its natural mineral composition. This is why spring water brands often advertise their unique mineral profiles, which are responsible for their distinct taste.
Mineral Water
Mineral water is also sourced from an underground, geologically protected source, but it is defined by a naturally occurring, specific minimum mineral content of at least 250 parts per million (ppm). The concentration and proportion of these minerals must remain constant at the source. Manufacturers are not permitted to add any minerals to this type of water, and processing is limited to removing unstable elements like iron or sulfur.
Common Demineralization Methods
There are several industrial-scale methods used to produce demineralized water. The most common include:
- Reverse Osmosis (RO): This process forces water through a semi-permeable membrane that has extremely small pores. The membrane traps dissolved minerals, salts, bacteria, and other contaminants, allowing only purified water to pass through. It is a very effective and widely used method for demineralizing water.
- Distillation: This classic method involves boiling water and collecting the resulting steam, which is then condensed back into a liquid. Because minerals and many other impurities have higher boiling points than water, they are left behind. Distillation is highly effective at removing minerals, but it is also energy-intensive.
- Deionization (DI): Deionization removes mineral ions from water using ion exchange resins. The water flows through two types of resins: a cation resin and an anion resin, which exchange their own hydrogen and hydroxyl ions for the mineral ions in the water. Deionization is excellent for removing mineral salts but is less effective at eliminating organic compounds or microorganisms.
Is Drinking Un-remineralized Demineralized Water Safe?
While occasional consumption of demineralized water is not harmful, long-term or exclusive reliance on it can pose health risks. The World Health Organization (WHO) has noted potential negative health effects associated with drinking demineralized or low-mineral water over time. These risks are primarily linked to the lack of essential minerals like calcium and magnesium that are otherwise obtained from a balanced diet and drinking water. Extended intake of low-mineral water may lead to mineral deficiencies and potential issues with the body's water-salt balance.
Fortunately, for consumers of bottled purified water, this risk is mitigated. Reputable bottled water brands that use demineralization processes for purification will reintroduce a balanced profile of minerals after processing to improve taste and nutritional value. This step ensures the final product is not only clean but also suitable for daily consumption.
Comparison of Bottled Water Types
| Feature | Purified Water | Spring Water | Mineral Water |
|---|---|---|---|
| Source | Municipal or ground water | Protected underground aquifer | Protected mineral spring |
| Demineralization | Yes, typically done to remove all contaminants | No, natural minerals are retained | No, natural mineral content is maintained |
| Re-mineralization | Yes, minerals are added back for taste | No, minerals are naturally present | No, minerals are naturally present |
| Mineral Content | Controlled and consistent, added back in | Naturally occurring, varies by source | Naturally high and consistent, defined by source |
| Taste Profile | Neutral and clean due to controlled mineral addition | Distinctive, based on source's natural minerals | Rich, based on high concentration of natural minerals |
How to Determine if Your Bottled Water is Demineralized
The easiest way to know if your bottled water has been demineralized is to read the label. Look for terms like 'purified,' 'reverse osmosis,' or 'distilled'. If the water is labeled 'spring water' or 'mineral water,' it has not been demineralized and retains its natural mineral content. Always review the bottle's label to understand its source and purification method.
Conclusion: The Final Word on Bottled Water
In summary, the answer to the question 'is bottled water demineralized?' is not a simple yes or no. It entirely depends on the type of bottled water you purchase. Purified water is indeed demineralized as part of its intense filtration process, but minerals are added back to make it palatable and suitable for drinking. Conversely, natural spring and mineral waters are bottled specifically to preserve their inherent mineral composition. For the average consumer, both options are safe for daily hydration as part of a balanced diet. However, knowing the distinction between these water types empowers you to make a more informed choice based on your preferences and health considerations.
