Demiwater and health

by Lara Fabrizi

Health risks from drinking of demineralised water

A community’s drinking water supply comes from ground and surface water sources. Every country's regulations require communities to treat and disinfect drinking water before distributing it to the public, because of the possible presence of pollutants (micro organisms, toxic minerals and metals, organic chemicals, radioactive substances, additives). Usually surface water has to undergo many more purification steps than groundwater to become suited to drink. Every country has its own legal drinking water standards. These prescribe which substances can be in drinking water and what the maximum concentrations of these substances are. The standards are called maximum contaminant levels. They are formulated for any contaminant that may have adverse effects on human health and each company that prepares drinking water has to follow them up. The main guidelines about drinking water standards are published by the World Health Organization (WHO) and by the European Union (EU).
There are several problems that can endanger the quality of the drinking water and some diseases can occur by drinking improperly treated water.
Even if the water is purified and cleaned, it can miss some minerals or desirable substances, not being fully appropriate for consumption. In fact, not all substances present in water are necessarily harmful to our health: some substances are health improving.
Water almost or completely free of dissolved minerals as a result of distillation, deionisation, membrane filtration, electrodialysis or other technology is called demineralised water.
There are many pros and cons on drinking demineralised water. The argument in favour of drinking it is that the minerals present in water intervene with our body functions. Many books are written by doctors and nutritionists claiming that the presence of minerals in drinking water causes disease. The arguments against drinking demineralised water are that we lost a primary source of necessary minerals in our diet and that water that has lost its own minerals will attract and absorb minerals in our body, causing a mineral deficit.

More information on drinking water standards and drinking water preparation

Drinking water hardness
When water is referred to as 'hard' this means that it contains more minerals than ordinary water. These are especially the minerals calcium (Ca) and magnesium (Mg). Hardness is expressed in terms of calcium carbonate (CaC03). Water with less than 75 milligrams per litre (mg/l) is considered soft, 76-150 mg/l moderately hard, and above 150 mg/l hard water.
The degree of hardness of the water increases when more calcium and magnesium dissolve. ‘Soft’ water is water that contains small amounts of calcium and magnesium. Some soft water is naturally occurring, but most of it is created by water softeners. A water softener is a unit that is used to soften water, by removing the minerals that cause the water to be hard. A water softener collects hardness minerals within its conditioning tank and from time to time flushes them away to drain. Ion exchangers are often used for water softening. When an ion exchanger is applied for water softening, it will replace the calcium and magnesium ions in the water with other ions, for instance sodium (Na) and potassium (K). The exchanger ions are added to the ion exchanger reservoir as sodium and potassium salts (NaCl and KCl).

More information on water softening

Health risks

There has been much publicity over the years about the negative health effects of drinking softened water, but recent research showed that the amount of salt consumed by drinking softened water is insignificant when compared to overall daily salt intake. Anyway over the past 25 years research has continued to amass in support of the beneficial role of minerals in water: studies of populations in areas of naturally occurring hard water and soft water have found few occurrences of cardiovascular diseases, cancer, diabetes, respiratory diseases or other health problems in hard water areas.
A domestic, innovative system, which can be used to get perfectly balanced proportions of minerals good for our health in drinking water, is provided by Lenntech. For more information go to our home water filter web page.

In the draft of the rolling revision of the WHO guidelines for drinking-water quality, titled ‘Health risks from drinking demineralised water’ by F. Kožíšek, the possible health consequences of low mineral content water consumption are divided in the categories: direct effects on the intestinal mucous membrane, practically zero calcium and magnesium intake, low intake of other elements, loss of calcium, magnesium and other essential elements in prepared food, possible increased dietary intake of toxic metals, possible bacterial re-growth.

More information on drinking water purification systems for domestic water

Direct effects on the intestinal mucous membrane

It has been demonstrated that consuming water of low mineral content has a negative effect on homeostasis mechanisms. Homeostasis literally means ‘same state’ and it refers to the process of keeping the internal body environment in a steady state. In his publication Kožíšek states that "experiments in animals have repeatedly shown that the intake of demineralized water leads to diuresis (increased urination caused by substances present in the kidney tubules), extra cellular fluid volume and serum concentration of sodium and chlorine ions and their increased elimination from the body, lower volumes of red blood cells and other hematocritic changes (alteration of the number of red blood cells)". A German study carried out by th German Society for nutrition proved instead that if distilled water is ingested, the intestine has to add electrolytes to this water, taking them from the body reserves. After the ingestion of distilled water the electrolytes dissolved in the body water are further dilute. Inadequate body water redistribution may compromise the function of vital organs.

In the past, acute health problems were reported in mountain climbers who had prepared their beverages with melted snow. which was not supplemented with necessary ions. A more severe course of such a condition coupled with brain oedema, convulsions and metabolic acidosis was reported in infants whose drinks had been prepared with distilled or low mineral bottled water (CDC 1994).

Practically zero calcium and magnesium intake
Calcium and magnesium are essential elements for our body. They can be provided to our organisms by food, but even the diets rich in calcium and magnesium intake may not be able to fully compensate their absence in drinking water.
Calcium is part of bones and teeth. In addition, it decreases neuromuscular excitability, is beneficial to the conducting myocardial system, heart and muscle contractility, intracellular information transmission and blood clotting. Osteoporosis is the most common manifestation of calcium deficiency; a less common but proved disorder attributable to Ca deficiency is hypertension.
Magnesium plays an important role as a cofactor and activator of more than 300 enzymatic reactions including glycolysis, ATP metabolism, transport of elements such as sodium (Na), potassium (K) and calcium through membranes, synthesis of proteins and nucleic acids, neuromuscular excitability and muscle contraction etc. It acts as a natural antagonist of calcium. Magnesium deficiency increases risk to humans of developing various pathological conditions such as vasoconstrictions, hypertension, cardiac arrhythmia, atherosclerotic vascular disease, acute myocardial infarction, preeclampsia in pregnant women, possibly diabetes mellitus of type II and osteoporosis (Rude, 1998; Innerarity, 2000; Saris et al, 2000).

Researches and studies proved that water low in magnesium can cause increased morbidity and mortality form cardiovascular disease, higher risk of motor neuronal disease, pregnancy disorders, preeclampsia. Water low in calcium may be associated with higher risk of fracture in children, certain neurodegenerative diseases, pre-term birth and low weight at birth. Lack both in calcium and in magnesium can also cause some types of cancer.

W ater hardness and cardiovascular disease

Over 80 observational epidemiological studies relating hardness and cardiovascular disease risks have been realized and their results had been discussed by experts at the meeting organized by the WHO European Centre in Rome on November 11-13, 2003. The conclusions are quoted in the WHO report titled: 'Nutrient minerals in drinking-water and the potential health consequences of long-term consumption of demineralized and remineralized and altered mineral content drinking-waters', published in August 2004.

It was observed a positive (protective) association between cardiovascular disease mortality and increased water hardness in countries around the world, both for population and on individual-basis. It was then supposed that these beneficial health effects can possibly be extended to large population groups on a long- term basis by adjusting the water quality.

It was pointed out that magnesium and possibly calcium may be effective in reducing blood pressure in hypertensive individuals. Nutritional studies suggest that some other micronutrients may have a beneficial role associated with their presence in drinking water, even is they have not extensively considered in these epidemiological studies yet. More studies are needed to better understand the possible risks and benefits of essential and trace elements found in water.

The discussion group concluded there is sufficient epidemiological evidence of and inverse relationship between magnesium concentration in drinking water and ischemic heart disease mortality, and therefore the reintroduction into demineralised water in the remineralisation process would likely provide health benefits. There are, in fact, no known harmful human health effects associated with the addition magnesium within a large range and the nutritional benefits are well known. It is thought that adding calcium provides the same benefits, however, a correlation between calcium in drinking water and decreases in the occurrence of heart disease is not yet proven substantially.

Low intake of some essential elements

The contribution of water to uptake of some essential elements for humans is important because the modern diets are often not an adequate source of some minerals. Moreover these minerals are often present in water as free ions, so they are more readily adsorbed from water compared to food. Recent epidemiological studies suggest that low mineral drinking water may be a risk factor for hypertension and coronary heart disease, gastric and duodenal ulcers, chronic gastritis, goitre, pregnancy complications and several complications in infants. A study of this kind conducted in 1992 by Lutai on two populations living in areas with different levels of dissolved minerals showed that the population of the area supplied with water low in minerals showed higher incident rates of these disease. Children living in this area exhibited slower physical development and more growth abnormalities, pregnant women suffered more frequently from oedema and anaemia.

High loss of calcium, magnesium and other essential elements in food prepared with low mineral water

If soft water is used for cooking it can cause substantial losses of all essential elements from food. In contrast, if hard water is used, the loss of these elements is much lower. Since the current diet of many people does not provide all the necessary elements in sufficient quantities, it is important to not loose essential elements and nutrients during cooking. Therefore, in the areas supplied with soft water, we have to take into account not only a lower intake of magnesium and calcium from drinking water but also a lower intake of magnesium and calcium from food due to cooking in such water.

Risk from toxic metals

Low mineralised water is highly aggressive to materials with which it comes into contact. It easily adsorbs metals and some organic substances from pipes, coatings, storage tanks and containers. Moreover, calcium and magnesium in water and food are known to have an antitoxic activity: they can prevent the absorption of some toxic elements from the intestine into the blood. Population supplied with low-mineral water may be at a higher risk in terms of adverse effect from exposure to toxic substances compared to populations supplied with water of average mineralization. Calcium and to a lower extent also magnesium in both drinking water and food were previously found to have a beneficial antitoxic effect since they prevent – via either a direct reaction resulting in an no absorbable compound or competition for binding sites – absorption or reduce harmful effects of some toxic elements such heavy metals.

Possible bacteria contamination of low-mineral water

The bacterial re-growth is encouraged by the lack of a residual disinfectant and by the possibly great availability of nutrients in aggressive water, such the low-mineral water, particularly if it has a high temperature.

Harmful effects of hard water

No evidence is available to document harm to human health from harder drinking water. Perhaps only a high magnesium content (hundreds of mg/l) coupled with a high sulphate content may cause diarrhea. Other harmful health effects were observed in water rich in dissolved solids (above 1000 mg/l of TDS) showing mineral levels that are not common in drinking water. In areas supplied with drinking water harder than 500 mg/l CaCO3, higher incidence rates of gallbladder disease, urinary stones, arthritis and arthropathies as compared with those supplied with softer water were reported (Muzalevskaya et al, 1993). An epidemiological study carried out in a particular region (Tambov) found hard water (more than 400-500 mg/l of CaCO3) to be possible cause of higher incidence rates of some diseases including cancer (Golubev et al, 1994).

Sensorial disadvantages of hard and soft water
Higher water hardness may worsen sensorial characteristics of drinking water or drinks and meals prepared with such water: formation of a layer on the surface of coffee or tea, loss of aromatic substances from meals and drinks (due to bonding to calcium carbonate), unpleasant taste of water itself for some consumers.
Very soft water, such as distilled and rain water as two extreme examples, is of unacceptable taste for most people who usually report it to be of unpleasant to soapy taste. A certain minimum content of minerals, the most crucial of which are calcium and magnesium salts, is essential for the pleasant and refreshing taste of drinking water.

Fluoride in drinking water

Most drinking waters contain some fluoride. Processes such anion exchange, demineralisation and some other treatments which will remove it, affecting its concentration.

High levels of excess fluoride intake cause crippling skeletal fluorosis. This is almost always associated with high fluoride intake from drinking water. Ingestion of excess fluoride during tooth development, particularly at the maturation stage, may also result in dental fluorosis.
The optimal drinking water concentration of fluoride for dental health is generally between 0.5 to 1.0 mg/litre and depend upon volume of consumption and uptake and exposure from other sources. These values are based on epidemiological studies. The WHO drinking water quality guideline value for fluoride is 1.5 mg/l. The US Environmental Protection Agency has set a Maximum Contaminant Level of 4.0 mg/l in the US based upon prevention of crippling skeletal fluorosis and a guidance of 2.0 mg/l to avoid moderate dental fluorosis.

A decision to use demineralised water as drinking water sources without addition of fluoride during remineralization will depend upon many factors: the concentration of fluorine in the existing local supply, the volume of water consumed, the prevalence of risk factors for dental caries, oral hygiene practices, level of public dental awareness, presence of alternative vehicles for dental care and fluoride available to the whole population.

Desirable mineral content of demineralised drinking water

In the late 1970’s, the issue of an optimum composition of drinking water, particularly if obtained by desalination, was in the centre of attention of the WHO. The WHO also emphasized the importance of mineral composition of drinking water and warned e.g. against the use of cation exchange sodium cycle softening in water treatment (WHO, 1978; WHO, 1979).

In the 1980’s the wave of interest in the effect of water hardness on cardio vascular diseases morbidity rather subsided; it seemed that any new insight into the issue could not be expected. The focus was on confirming the role of magnesium as a crucial factor of hardness and on first attempts of more general quantification of its protective effect.

In the 1990 criticisms of the existing studies started to make a new challenge to publications of further studies. These critics asserted that morbidity was evaluated at a population group based level, rather than at an individual-based level and individual exposure to calcium and magnesium from water was not established. In other studies, the confounders possibly involved in cardio vascular diseases morbidity such as age, socio-economic factors, alcohol consumption, eating habits, climatic conditions etc. were not adequately taken into account.

Most new epidemiological studies of the 1990’s were able to specify the effect of either calcium or magnesium and also focused on morbidity other than cardio vascular diseases. During the 90’s research confirmed a protective effect of both drinking water magnesium and calcium against cardio vascular diseases, and more data on beneficial effect of these elements in drinking water on human health were presented.

More recent studies have provided additional information about minimum and optimum levels of minerals that should be in demineralised drinking water. These studies suggest for magnesium a minimum of 10 mg/l and an optimum of 20-30 mg/l, for calcium a minimum of 20 mg/l and an optimum of about 50 mg/l, for fluoride an optimum of 0.5 – 1 mg/l and a maximum of 5 mg/l. For total water hardness the sum of calcium and magnesium should be 200 to 400 mg/l.

At these concentrations, minimum or no adverse health effects were observed and the maximum protective or beneficial health effects of drinking water appear to occur.

Conclusion and recommendations
Minerals are important parts of drinking water and are of both direct and indirect health significance. Sufficient evidence is now available to confirm that a certain minimum amount of minerals in water is desirable, since their deficiency have many negative health effects: diseases and possible aggression from toxic elements and bacteria.
The optimum Ca and Mg levels in drinking water should lie within the following ranges: from 20 to 30 mg/l for Ca and from 40 to 80 mg/l for Mg and from about 200 to 400 mg/l for water hardness.
Unfortunately, over the past two decades little research attention has been given to the beneficial or protective effects of drinking water substances.
As recommended in the rolling revision of the WHO guidelines for drinking water quality, titled: ‘Nutrient minerals in drinking-water and the potential health consequences of long-term consumption of demineralised and remineralized and altered mineral content drinking-waters’, there is a need for more precise data on the impact of water composition and intake under a broader range of physiologic and climatic conditions, in order to more precisely evaluate the importance of minerals in drinking water on mineral nutrition. Additional studies should be conducted on potential health consequences associated with consumption of both high and low mineral content waters in addition to consideration of water hardness. When studies are conducted, investigators should consider exposures to both calcium and magnesium levels in combination with other minerals and trace elements that may be present in hard and soft waters. National governments and water suppliers should be encouraged to practice stabilization of demineralised water with additives that will increase calcium and magnesium levels and to conduct studies that monitor public health impacts. Community and bottled water suppliers should provide information to the general public and health professionals on the composition of water for constituents including possibly beneficial substances. Water bottlers should also consider providing waters with mineral compositions that are beneficial for population segments.

For all you questions on demineralised water move to the demineralised water FAQ or look at our demiwater web page.

For further information of mineral water click here.

Related topics

Mineral water composition


Bottled water

Pure water

Alternative drinking water sources

Drinking water FAQ

Drinking water standards


  • C. Ingram, The drinking water book, Ten Speed Press, 1991

  • F. Kožíšek, Health risks from drinking demineralised water, WHO, 2004

  • F. Kožíšek, Health significance of drinking water calcium and magnesium, National Institute of Public Health, February 2003

  • Consensus of the meeting August 2004, Nutrient minerals in drinking-water and the potential health consequences of long-term consumption of demineralized and remineralized and altered mineral content drinking-waters, WHO

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