Nutrients in potable water


Water, sanitation, health and the environment.





In November 2003, a group of experts in nutrition and medicine gathered in Rome (the European Center for Environment and Health) to work on issues related to the composition of drinking water and its possible contribution to the total supply of nutrients. The initial objective of this meeting was to contribute to the development of the Guidelines for the Healthy and Environmentally Safe Desalination of Water, introduced by the WHO Eastern Mediterranean Regional Office, for the preparation of the 4th edition of the WHO Drinking Water Quality Guidelines (DWCP).

In particular, the question arose about the consequences of long-term use of demineralized water: on sea water and brackish water subjected to desalination, on fresh water processed in the membrane system, and on recreating their mineral composition.


As a rule, drinking water is subjected to one or several treatments before delivery to the consumer in order to achieve appropriate safety performance and improve aesthetic properties. Fresh water is usually subjected to coagulation, sedimentation, filtration through granular materials, adsorption, ion exchange, membrane filtration, slow filtration through sand, disinfection, sometimes softening. The receipt of drinking water from highly saline waters such as marine and brackish waters through desalination is widely practiced in regions experiencing its acute shortage. This technology, in the face of ever-increasing consumption of water, is becoming more attractive from an economic point of view. More than 6 billion gallons of demineralized water are produced every day in the world. Remineralization of such water is mandatory: it is aggressive in relation to distribution systems. If remineralization of desalinated water is a prerequisite, a logical question arises: are there water treatment techniques that can restore the content of some important minerals?




The health consequences of using demineralized drinking water


František Kolízek


National Institute of Public Health


Chech Republic


I. Introduction



Artificially treated demineralized water, which was originally obtained by distillation and then by reverse osmosis, should be used for industrial, technical and laboratory purposes. Water treatment technologies began to be widely used in the 60s of the last century in coastal and inland areas. This is due to the shortage of natural water supplies and the increasing consumption of water due to demographic growth, higher standards of quality of life, industry development and mass tourism. Demineralization of water is needed when available water resources are represented by highly mineralized brackish or sea water. The problem of drinking water on ocean liners and spacecraft was always topical. The above treatment methods were previously used to provide water exclusively for these objects because of technical complexity and high cost.



In this chapter, demineralized water is understood to mean water completely or almost entirely freed from dissolved minerals by distillation, deionization, membrane filtration (reverse osmosis or nanofiltration), electrodialysis, etc. The composition of the dissolved substances in such water can vary, but their total content should not be More than 1 mg / l. The electrical conductivity is less than 2 mS / m3 * and even less (<0.1 mS / m3). Initially, it was clear that the treated water is not suitable for use without additional mineral enrichment:

- demineralized water is very aggressive, it must be neutralized; Otherwise, it can not be fed to the distribution system, passing through the pipes and storage tanks. Aggressive water destroys pipes and flushes metals and other materials out of them;



- distilled water has "poor" flavor characteristics;



- it was proved that some substances present in drinking water are important for the human body.



After assessing the hygienic, organoleptic properties and other information, the scientists gave recommendations on the composition of the demineralized water:



1) min. Mineralization of 100 mg / l; the content of hydro carbonate ions is 30 mg / l; calcium 30 mg / l; 2) the optimum dry residue (250-500 mg / l for chloride-sulfate waters and 250-500 ml for hydro carbonate waters); 3) the maximum level of alkalinity (6.5 meq / l), sodium (200 mg / l), boron (0.5 mg / l) and bromide ion (0.01 mg / l). Some of the recommended values are discussed in more detail in this chapter.



Demineralized water undergoes further processing: various salts are added to it, for example, calcium carbonate or limestone; Mix with small volumes of highly mineralized water to improve taste characteristics and reduce aggressiveness in relation to distribution networks and sanitary equipment.



Some brands of bottled drinking water are demineralized water, enriched subsequently with mineral substances to give it a favorable taste characteristics. People who consume this water may not receive the minerals present in the more highly mineralized water.


II. Health risk from the use of demineralized or slightly mineralized water

Demineralized water, which was not subsequently enriched with minerals, is an extreme case. It contains dissolved substances, such as calcium and magnesium, which make the main contribution to stiffness, in very small quantities.


Possible consequences of consumption of water, poor in mineral substances, fall into the following categories:


- direct effect on the intestinal mucosa, metabolism, and homeostasis of minerals, and other functions of the body;


- low intake/absence of calcium and magnesium;


- a small supply of another macro- and microelements;


- loss of calcium, magnesium and other macro elements during cooking;


- a possible increase in the intake of toxic metals into the body.


1. Direct effects on the intestinal mucosa, metabolism, and homeostasis of minerals, and other body functions

Distilled and slightly mineralized water (total mineralization <50 mg / l) can be unpleasant to taste, but over time, the consumer gets used to it. Such water does not quench thirst well (3).


The results of the experiment carried out by the scientists of WHO in human volunteers showed a similar pattern (3), which allowed us to outline the main mechanism of the effect of water with mineralization up to 100 mg / l on the exchange of water and minerals:


1) increased diuresis (by 20% compared with the norm), the level of fluid in the body, the concentration of sodium in the serum; 2) decreased potassium concentration in the serum; 3) increased excretion of sodium, potassium, chloride, calcium and magnesium from the body.


Incorrect distribution of fluid in the body can affect even the functions of vital organs. The first signals - fatigue, weakness, and headache; More serious - muscle cramps and heart rhythm disturbance.


2. Low intake/absence of calcium and magnesium

Epidemiological studies conducted in different countries over the past 50 years have shown that there is a correlation between the increased number of cardiovascular diseases, followed by death and consumption of soft water. Recent studies have shown that consumption of soft water, for example, by poor calcium, can lead to an increased risk of fractures in children (16), neurodegenerative changes (17), premature birth and reduced weight of newborns (18) and some cancers (19.20). In addition to the increased risk of sudden mortality (21-23), with the use of water poor in magnesium, cases of cardiac muscle disruption (24), late toxicosis of pregnant women (so-called preeclampsia) (25), and some cancers (26-29).


1. WHO Report of 1980

Drinking water with low salinity helps wash out salts from the body. Changes in the water-salt balance in the body were noted not only with the use of demineralized water, but also water with mineralization from 50 to 75 mg / l. Therefore, a team of WHO researchers who prepared a report for 1980 (3) recommends drinking water with mineralization of at least 100 mg / l for drinking purposes. Also, scientists concluded: the optimal mineralization is 200-400 mg / l for chloride-sulphate waters and 250-500 mg / l for hydro carbonate waters (1980, WHO).


2. Current recommendations

These results support the assumption that the magnesium content in drinking water should be at least 10 mg / L, calcium 20 mg / L, and not 30 mg / L, as stated in the WHO report for 1980.


Based on the available data, the researchers recommended the following concentrations of calcium, magnesium and the amount of hardness of drinking water:


- for magnesium: at least 10 mg / l (33.56), the optimum content of 20-30 mg / l (49, 57);


- for calcium: at least 20 mg / l (56), the optimal content is about 50 (40-80) mg / l (57, 58);


- total hardness of water, the total content of calcium and magnesium salts is 2-4 mmol / l (37, 50, 59, 60).


V. Conclusions

Drinking water should contain at least the minimum quantities of important minerals (and some other components, for example, carbonates).


This issue is relevant not only for demineralized drinking water, which was not enriched with a complex of minerals but also for water in which the mineral content is reduced due to domestic or centralized treatment, as well as for slightly mineralized bottled water.


Potable water obtained by demineralization is enriched with minerals, but this does not apply to water treated at home. Even after stabilizing the mineral composition, water may not have a beneficial effect on health. Usually, water is enriched with mineral substances, passing through limestone or other carbonate-containing minerals. Water at the same time is saturated mainly with calcium, and the deficiency of magnesium and other trace elements, for example, fluorine and potassium, is not replenished. In addition, the amount of calcium introduced is regulated more by technical ones (reduced water aggressiveness) than by hygienic considerations. Perhaps, none of the ways of artificial mineral enrichment with mineral substances is optimal, because all important mineral substances do not saturate. As a rule, the methods for stabilizing the mineral composition of water are designed to reduce the corrosive activity of demineralized water.


Unimplemented demineralized water or water with a low mineral content - in the light of the lack or absence of important minerals in it - is by no means an ideal product, hence its regular consumption does not adequately contribute to the overall consumption of some significant nutrients. This chapter substantiates this statement. Confirmation of experimental data and discoveries obtained by human volunteers in the study of highly demineralized water can be found in earlier documents that do not always correspond to modern methodological requirements


There is evidence that a higher magnesium content in water leads to a lower risk of cardiovascular disease and sudden death.


In addition to the increased risk of death from cardiovascular diseases, low magnesium content in water is associated with possible diseases of the motor nerves, pregnancy complications (so-called preeclampsia), the sudden death of small children and some types of cancer. Modern researchers suggest that the use of soft water with a low calcium content can lead to fractures in children, neurodegenerative changes, premature birth, the low body weight of newborns and some types of cancer. It is impossible to exclude the role of aqueous calcium in the development of cardiovascular diseases.


International and national organizations responsible for the quality of drinking water should consider a manual for the treatment of demineralized water, necessarily determining the minimum values of important indicators, including calcium, magnesium, and mineralization. If necessary, plenipotentiaries are required to support and promote targeted research in this area to improve the health of the population. If a quality manual is developed for individual substances that are mandatory in demineralized water, plenipotentiaries should be sure that the document is applicable to consumers of domestic water purification systems and bottled water.