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Deionized water is a highly purified form of water that has undergone a deionization or demineralization process by one or more different methods. Some of these methods include micro or nano filtration through semi-permeable membranes (a process known as reverse osmosis) and water filtration through ion exchange columns.
In simple terms, deionized water is one of the purest forms of water that we can access with our current technology. This type of water is frequently used in industry, in some technical applications and in chemical laboratories. This is because many of these processes are sensitive to the presence of certain ions in the water. But is this form of water safe to drink?
Deionized water vs. potable water
It may sound strange, but most of the water we find in nature, including natural drinking water and water that has been made drinkable by artificial means, is not pure. Although it is true that its main component is water (H 2 O), it is actually a solution that contains various dissolved salts, as well as organic compounds. It may even contain some microorganisms in suspension.
In contrast, deionized water has been subjected to a process that removes most of the ions (both cations and anions) that are naturally dissolved in water. In some cases, although not always, it is also possible to eliminate most of the organic substances present.
This can generate the following doubt. If drinking water is not pure but is safe to drink, can the same be said for deionized water, or will the impurities that drinking water often contains be necessary to make it safe?
The answer to this question is that it depends. It largely depends on how much and how often the deionized water is drunk. Drinking a couple of glasses of deionized water probably won’t have any noticeable effect in the short term. However, drinking deionized water on a regular basis instead of drinking water does carry some risks.
Different degrees of purity of deionized water
When considering the possible adverse effects of deionized water on the body, it should be noted that there are different levels of purification or deionization. This means that not all DI water samples are the same and neither are their effects on the body. The final composition of a sample of this type of water will depend on many factors, among which we can mention:
- The original composition of water subjected to deionization.
- Whether the water was previously distilled or not.
- The particular technology that was used during deionization.
- The number of deionization cycles that the water sample was subjected to.
Depending on these variables, deionized water samples can be obtained with ion concentrations as low as 10 -7 molar and a total carbon concentration (which measures the amount of organic matter present) as low as 5 parts per billion or 5 μg/ L (0.005mg/L). In these cases, the water is often referred to as ultrapure water, milliQ water, or 18 MOhm/cm water. In other cases, the samples may have solid concentrations of the order of 10 mg/L, so it is safe to assume that some waters are more deionized than others.
With that said, we will discuss the negative effects of drinking ultrapure deionized water below.
The dangers of drinking deionized water
Drinking deionized water can be harmful to the body of any living being for different reasons. The most important ones are:
May affect the homeostatic ionic balance of the body
Ultrapure water is rapidly absorbed from the intestine and can alter the ionic concentration of the blood. This, in turn, has the ability to alter the ionic and water balance in different parts of the body, especially if you drink constantly.
Adverse effects on the intestinal mucosa have been reported.
Some research papers showed that giving ultrapure water to rats caused damage to the epithelial cells of their intestine, probably due to osmotic shock. This occurs when large amounts of water enter the cell due to abnormally low extracellular osmotic pressure , eventually bursting the cell. However, few studies have been able to confirm these observations.
May encourage seeking unhealthy sources of hydration
A characteristic of deionized water is that it has an unpleasant taste. Also, it is not as good as regular drinking water for quenching thirst. As a result, people who only have access to deionized water tend to drink less water and replace it with other sources of hydration that may be less healthy, such as highly sugary fizzy drinks.
Deficiency of calcium, magnesium and other micronutrients
Drinking water always contains variable amounts of Ca 2+ and Mg 2+ ions and other nutrients that are essential for the body. Substituting deionized water for normal drinking water reduces our intake of these nutrients, which can lead to a deficiency that endangers our health.
Loss of essential ions in foods cooked with deionized water
The effect of deionized water not only occurs if we consume the water directly, but can also affect us indirectly if we cook our food in deionized water. This is because, being so pure, deionized water is capable of extracting many solutes or ions from our food during cooking, such as calcium and magnesium. If the cooking water is not part of the recipe, all those ions and other nutrients will be lost along with the water.
Possible contamination with heavy metals
Deionized water itself does not contain appreciable amounts of toxic heavy metals such as lead or mercury. However, due to its very purity, and as explained in the case of food, deionized water is capable of extracting metals and other minerals from pipes and containers that serve as containers, representing a risk of contamination with heavy metals.
How to make deionized water drinking water?
In many countries around the world, deionization of seawater is the main source of drinking water. However, this does not present a significant risk, as deionized water can easily be made into potable water. All that is needed is to dissolve some essential salts in it until reaching a concentration that is considered drinkable.
In this sense, the World Health Organization (WHO) recommends that drinking water have certain minimum levels of salts, calcium and bicarbonate ions that are presented in the following table:
| Water quality parameter | minimum levels |
| Total dissolved salts: | 100mg/L |
| Bicarbonate ion concentration: | 30mg/L |
| Ca 2+ ion concentration | 30mg/L |
Although a minimum salt level of 100 mg/L is recommended, the recommended optimal level is between 200 and 500 mg/L. Fortunately, it is very easy to achieve these salt levels by treating the deionized water with calcium carbonate or limestone, as well as mixing the deionized water with small amounts of more mineral-rich water.
References
Aquae Foundation. (2021, December 28). Distilled water – Properties and differences . https://www.fundacionaquae.org/wiki/what-is-distilled-water/
Kozisek, F. (sf). HEALTH RISKS FROM DRINKING DEMINERALIZED WATER . National Institute of Public Health. https://www.who.int/water_sanitation_health/dwq/nutrientschap12.pdf
Lenntech. (nd). Deionized/demineralized water . https://www.lenntech.es/aplicaciones/proceso/desmineralizada/agua-desionizada-desmineralizada.htm
The Risks and Benefits of Deionized Water . (2021, June 8). Office H2O. https://www.officeh2o.com/2020/11/11/the-risks-and-benefits-of-deionized-water/
US Water Systems. (nd). Can You Drink Deionized Water . https://www.uswatersystems.com/can-you-drink-deionized-water
