Nutrients in Drinking Water

Nutrients in Drinking Water

Water, Sanitation and Health

Protection and the Human Environment

World Health Organization 

Geneva

 

WHO Library Cataloguing-in-Publication Data

Nutrients in drinking water.

1. Water supply. 2. Potable water. 3. Water treatment. 4. Nutrition. 5. Micronutrients. I. World Health Organization.

ISBN 92 4 159398 9 (NLM classification: WA 687)

© World Health Organization 2005

  

  

TABLE OF CONTENTS

Preface .........................................................i

Acknowledgements .....................................iii

 

1. NUTRIENTS IN DRINKING WATER -
Consensus at Meeting .................................. 1

I. Introduction..................................................1

II. Topics Examined in the Meeting............................................................3

III. Drinking Water and Health Relationships..................................................6

IV. Conclusions and Recommendations .......................................10

 

2. DESALINATION GUIDELINES DEVELOPMENT FOR DRINKING WATER BACKGROUND 

(Joseph A. Cotruvo).........................................13

I. Introduc......................................................13

II. Drinking Water Production....................................................13

III. Desalination Technologies................................................16

IV. Membranes..............................................17

V. Distillation Technologies.................................................17

VI. Other Systems ........................................18

VII. Potential Technical Issues Associated With Desalination..................................................19

VIII. Petroleum Contamination..............................................20

IX. Conclusion .............................................23

 

3. WATER REQUIREMENTS, IMPINGING FACTORS AND RECOMMENDED INTAKES (Ann C. Grandjean)................................................ 25

I. Introduction................................................25

II. Adverse Consequences of Inadequate Water Intake, Requirements for Water, and Factors that Affect Requirements................................................25

 

4. ESSENTIAL NUTRIENTS IN DRINKING WATER

(Manuel Olivares & Ricardo Uauy) ...........................................41

I. Introduction................................................41

II. Definition of Nutritional Requirements and Recommendations........................................41

III. What are the Important Dietary Minerals and Electrolytes in the Diet and Potentially in Water
that are Essential for Nutrition and Wellbeing?.....................................................43

IV. What are the RDAs for Minerals and Electrolytes
and how are they determined? ...............44

 

5. MINERALS FROM DRINKING WATER: BIOAVAILABILITY FOR VARIOUS WORLD POPULATIONS AND HEALTH IMPLICATIONS (Choon Nam Ong) ........ 61

I. Introduction................................................61

II. Studies in Asia..........................................61

III. Studies in Pan-America ..........................63

IV. Studies in Africa .....................................64

V. Studies in North America.........................64

VI. Studies in Europe ...................................65

VII. Studies in the Western Pacific Region...68

VIII. Conclusion ............................................68

 

6. THE CONTRIBUTION OF DRINKING WATER TO TOTAL DAILY DIETARY INTAKES OF SELECTED TRACE MINERAL NUTRIENTS IN THE UNITED STATES (Joyce Morrissey Donohue, Charles O. Abernathy, Peter Lassovszky, George Hallberg) ........................................................ 75

I. Introduction..................................................75

II. Sources of Information .............................76

III. Data and Analysis......................................77

IV. Results........................................................80

V. Conclusions ...............................................88

 

7. MINERAL ELEMENTS TO CARDIOVASCULAR HEALTH

(Leslie M. Klevay & Gerald F. Combs) ........ 92

I. Introduction..................................................92

II. Nutritional Determinants of Heart Disease Risk....92

III. Water and Heart Disease ............................93

IV. Other Illnesses Related to Water Mineral Content.......93

V. Hardness Good or Softness Bad?..............93

VI. Trace Elements in Water Supplies............................................................94

VII. Conclusion ................................................95

 

8. STUDIES OF MINERAL AND CARDIAC HEALTH IN SELECTED

POPULATIONS (Floyd J. Frost) ...................... 101

I. Introduction.....................................................101

II. Magnesium Deficiency...................................101

III. Calcium, Copper, and Zinc Deficiencies ........................103

IV. Magnesium, Strenuous Exercise, and Sudden Cardiac Death..............................................103

V. Conclusions ...................................................103

 

9. HOW TO INTERPRET EPIDEMIOLOGICAL ASSOCIATIONS

(Gunther F. Craun & Rebecca L. Calderon) .................................... 108

I. Introduction..............................................108

II. Types of Epidemiological Studies ........109

III. The Exposure-Disease Association ....111

IV. Causality of an Association..................113

V. Web of Causation ..................................114

VI. Conclusions ..........................................114

 

10. WATER HARDNESS AND CARDIOVASCULAR DISEASE: A REVIEW OF THE EPIDEMIOLOGICAL STUDIES, 1957-78

(Rebecca L. Calderon & Gunther F. Craun) .................................... 116

I. Introduction.............................................116

II. Scientific Reviews by Expert Groups.....116

III. Summary of the Epidemiological Studies.......................................................118

IV. Strength of Association .......................121

V. Exposure-Response Relationship .......122

VI. Specificity of the Association .............122

VII. Reversibility .........................................122

VIII. Biological Plausibility ........................123

IX. Conclusions ..........................................123

 

11. DRINKING WATER HARDNESS AND CARDIOVASCULAR DISEASES: A REVIEW OF THE EPIDEMIOLOGICAL STUDIES, 1979-2004

(Silvano Monarca, Francesco Donato, Maria Zerbini) ................................... 127

I. Introduction.........................................127

II. Methods..............................................128

III. Results...............................................128

IV. Discussion.........................................130

V. Conclusions .......................................133

 

12. HEALTH RISKS FROM DRINKING DEMINERALISED WATER

(Frantisek Kozisek) .............................. 148

I. Introduction.........................................148

II. Health Risks from Consumption of Demineralised or Low-mineral Water .........................150

III. Desirable Mineral Content of Demineralised Drinking Water ................................................155

IV. Guidelines and directives for calcium, magnesium, and hardness levels in drinking water ....................157

V. Conclusions ......................................158

  

13. NUTRIENT MINERALS IN DRINKING WATER: IMPLICATIONS FOR THE NUTRITION OF INFANTS AND YOUNG CHILDREN (Erika Sievers) ..........164

I. Introduction...........................................164

II. Assessment of Mineral Intake in infant Nutrition.....................................................164

III. The Quantitative Intake of Drinking Water in
Infancy and early Childhood ........................165

IV. The Contribution of Drinking Water to Nutrient Mineral Intake in Infancy and Early

Childhood.................................................169

V. Conclusions .........................................175

 

14. FLUORIDE (Michael Lennon, Helen Whelton, Dennis O'Mullane, Jan Ekstrand) ....................... 180

I. Introduction............................................180

II. Fluoride Intake in Humans...................180

III. Dental Effects of Ingested Fluoride ....181

IV. Ingested Fluoride and Health .............182

V. Implications of Desalination.................182

VI. Conclusion ...........................................183

  

PREFACE

 

The World Health Organization assembled a diverse group of nutrition, medical and scientific experts in Rome in November 2003, at the WHO European Centre for Environment and Health, to address a number of questions relating to the nutrient composition of drinking water and the possibility that drinking water could in some circumstances contribute to total dietary nutrition. The original impetus of the meeting was as a contribution to development of Guidance on health and environmental aspects of desalination that was initiated by the WHO Eastern

Mediterranean Regional Office, and
intended ultimately to contribute to the development of the 4th edition of the WHO Guidelines for Drinking Water Quality (GDWQ). There were 18 invited experts from Canada, Chile, Czech Republic, Germany, Ireland, Italy, Moldova, Singapore, Sweden, United Kingdom and United States of America. Additional papers were provided by invitees who could not attend. The task was to examine the potential health consequences of long term consumption of water that had been ‘manufactured’ or ‘modified’ to add or delete minerals.

In particular, the meeting originated from
the question of the consequences of the
long-term consumption of waters that had
been produced from demineralization
processes like desalination of seawater
and brackish water as well as possibly
some membrane treated fresh waters, and
their optimal reconstitution from the
health perspective.

The scope of the review included these
questions:

• What is the potential contribution of drinking water to human nutrition?

• What is the typical daily consumption of drinking water for individuals, considering

climate, exercise, age and other factors?

• Which substances are found in drinking
water that can contribute significantly to
health and well-being?

• Under what conditions can drinking
water become a significant contribution to
the total dietary intake of certain beneficial substances?

• What conclusions can be drawn about
the relationship between calcium,
magnesium and other trace elements in
water and mortality from certain types
of cardiovascular disease?

• For which substances, if any, can a case
be made from the public health
perspective for supplementation of the
mineral content of treated drinking water
derived from demineralized water?

• What is the role of fluoride in such water
with respect to dental benefits, dental
fluorosis and skeletal fluorosis?

Drinking water is usually subjected to one or more treatment processes aimed at improving its safety and/or its aesthetic quality. Fresh waters can be treated by one or more processes such as coagulation, sedimentation, granular media filtration, adsorption, ion exchange, membrane

filtration, slow sand filtration, and
disinfection, and sometimes softening. The conversion of high salinity waters like
seawater and brackish waters to potable
water by desalination is being increasingly practiced in water-short areas as demand
for water increases, and the technology

becomes more economically attractive.
More than 6 billion gallons of desalinated
water are produced daily throughout the world.

Remineralization of desalinated water is
necessary to control its aggressiveness to
piped distribution systems. Since
remineralization of desalinated water is
required, a logical question is: are there methodologies that could bring with them

additional benefits such as by
reconstituting certain important minerals?

Natural waters are of widely diverse compositions depending upon their geologic and geographical origin and the treatments that they have undergone. For example, rain waters and some rain water-dominated surface waters have very low salinity and mineralization, whereas some ground waters can become highly, and sometimes excessively mineralized. If remineralization of processed water is desirable for health reasons, another logical question is whether some natural waters would also be more healthful if they also contained appropriate amounts of beneficial minerals.

The meeting concluded that only a few minerals in natural waters had sufficient concentrations and distribution to expect that their consumption in drinking water might sometimes be a significant supplement to dietary intake in some populations. Magnesium and possibly calcium were the two most likely significant contributors to dietary intake in populations that consumed ‘hard’ water. Information was provided on about 80 of many epidemiology studies of varying quality over the last 50 years that had addressed the issue of hard water consumption and possibly reduced incidence of ischemic cardiovascular disease in populations. Although the studies were mostly ecological and of varied quality, the meeting concluded that on balance they indicated that the hard water /CVD beneficial hypothesis was probably valid, and that magnesium was the more likely positive contributor to the benefits. This conclusion was supported by several case control studies as well as clinical studies. There were other possible health benefits that had been reported, but there was not sufficient data in hand to address those matters. The meeting also concluded that before making a Guidance determination, WHO should undertake a more detailed assessment of that hypothesis to include an examination of its biological plausibility. A follow-up symposium and meeting is being planned in 2006 to address that recommendation.

In respect to fluoride, the meeting concluded that optimal levels of fluoride intake from water are known to contribute beneficially to dental health. It also noted that higher intake levels can contribute to dental fluorosis, and much higher levels cause skeletal fluorosis. It concluded that a decision to remineralize demineralized water with fluoride would depend upon: the concentration of fluoride in the existing water supply, the volume of water consumed, the prevalence of risk factors for dental caries, oral hygiene practices and the level of public dental health awareness in the community, and the presence of alternative vehicles for dental care and fluoride available to the population.

ACKNOWLEDGEMENTS

 

WHO wishes to express its appreciation to Houssain Abouzaid, Coordinator, Healthy

Environments, in the WHO Eastern
Mediterranean Regional Office, for
initiating the desalination guidance
development process, and to Roger
Aertgeerts, WHO European Regional
Advisor for Water and Sanitation, and
Helena Shkarubo of the WHO Rome
office for hosting the meeting.

Joseph Cotruvo, USA, and John Fawell, UK, organized the meeting. Professor Choon Nam Ong, Singapore, chaired the meeting. Gunther Craun, USA, contributed to the document editing and reviews of comments.

Specific thanks are due to the experts that participated in the WHO Workshop on
'Nutrient Minerals in Drinking Water',
whose work was crucial to the
development of this document:

Rebecca Calderon, Gerald Combs, Gunther Craun, Jan Ekstrand, Floyd Frost, Ann Grandjean,

Suzanne Harris, Frantisek Kozisek, Michael Lennon, Silvano Monarca, Manuel Olivares, Denis O'Mullane, Souleh Semalulu, Ion Shalaru and Erika Sievers.

WHO especially wishes to acknowledge
the organizations that generously
sponsored the meeting. These included:
the International Life Sciences Institute
(ILSI), the U.S. Environmental
Protection Agency’s Office of Science and Technology (Washington), and Office of
Research and Development (Research
Triangle Park, North Carolina), the
American Water Works Association

Research Foundation, the Center for
Human Nutrition at the University of
Nebraska Medical Center (Omaha),
and Health Canada’s Water Quality
and Health Bureau (Ottawa, Ontario).

1. NUTRIENTS IN DRINKING 

WATER

 

Potential Health Consequences Of 

Long-Term Consumption Of 

Demineralized, 

Remineralized And Altered Mineral 

Content Drinking Water

Expert Consensus Meeting Group 

Report

  

__________________________

 

I. INTRODUCTION

 

Desalination of sea water and brackish
water is widely practiced and it is rapidly
growing as the principal source of new fresh water in the world. Water treatment processes including desalination followed by remineralization alter the mineral composition of drinking water compared to water derived from many fresh water sources.

The WHO Guidelines for Drinking-water Quality (GDWQ) provide a point of reference for drinking water quality regulations and standards setting world-wide. The Guidelines are kept up to-date through a process of ‘rolling revision’ that includes the development of
accompanying documents substantiating
the content of the guidelines and
providing guidance on experience with
good practice in achieving safe drinking-
water. This plan of work includes the
development of guidance on good
practices of desalination as a source of
safe drinking water.

In 1999, WHO’s Eastern Mediterranean Regional Office initiated a proposal to
develop WHO "Guidance for Safe Water:
Health and Environmental Aspects of
Desalination", because numerous existing facilities had developed on a case-by-case
basis with potentially inconsistent

consideration of important principles of
siting, coastal zone protection, chemicals
and contact surfaces used in plant
operation, water treatment and plant
construction , contaminants, water

distribution, microbial control and final
product water quality. International
guidance would reduce ad hoc decision

making and facilitate informed
decision making, assist the provision
of higher quality water, assure
higher quality water, assure consideration of environmental protection factors, reduce costs and allow more rapid project completion. Such guidance would be timely given the rapidly
increasing application of desalination world-wide. In 2000, the proposal to proceed was endorsed at a WHO Guidelines for Drinking-water Quality Committee meeting in Berlin, 

Germany. In May 2001, the proposal was examined at a dedicated expert consultation in Manama, Bahrain and an operating plan and program were proposed. This report and its supporting papers were the product of an meeting conducted in the WHO office for the European Region in Rome, Italy in 

2003. That meeting was part of the development plan for the Desalination Guidance describe above.

Health considerations addressed in this report are those potentially arising from long-term consumption of water that has undergone major alteration in its mineral content, such that it must be remineralized to be compatible with piped distribution systems. The report also considers the relationships between calcium and magnesium in drinking water on certain cardiovascular disease risks. In addition there also a brief review of fluoride in remineralized water and dental effects in relation to associated water consumption.

1. Background

Drinking water, regardless of its source, may be subjected to one or more of a variety of treatment processes aimed at improving its safety and/or aesthetic quality. These processes are selected in each case according to the source water and the constituents and contaminants that

require removal. Surface fresh waters will
often undergo coagulation, sedimentation,
rapid sand filtration and disinfection.  

Ground waters, which are often naturally
filtered, usually undergo less treatment
that could be limited to disinfection alone.
Other treatment processes may include
pH adjustment, softening, corrosion
control chemicals addition, alkalinity
adjustment, carbon filtration/adsorption, membrane filtration, slow sand filtration
and supplemental fluoridation. The
disinfectants applied could include
chlorine, chlorine dioxide, ozone, or
chloramines. Some substances will be
added by the chemicals used for
treatment, i.e. direct and indirect additives.

For waters with high salinity (e.g. from 
perhaps 1000 ppm up to about 40,000 
ppm) such as brackish waters or sea 
water, treatment processes must remove
most of the dissolved salts in order to
make the water potable. The major

methods include reverse osmosis, other membrane treatments or several
distillation/vapor condensation
processes. These processes require 
extensive pretreatment and water
conditioning and subsequent
remineralization, so that the finished
water that is now significantly
different from the source water will
not be overly aggressive to the piped
distribution systems that it will pass
through on the way to consumers.

In the course of treatment of fresh water, contaminants and some potentially 
beneficial nutrients will be removed and 
some might be added. Other waters, 
such as those treated by softening or 
membrane filtration may also undergo 
significant changes in their mineral 
content due to the treatment processes.

Remineralization and increasing alkalinity for the purpose of stabilizing and reducing

corrosivity of water from which dissolved solids have been substantially reduced are often accomplished by use of lime or 

limestone. Sodium hydroxide, sodium bicarbonate, sodium carbonate, 

phosphates, and silicates are also 

sometimes used alone or in combination. 

The mineral composition of limestone is 

highly variable depending upon the 

quarry location and it is usually 

predominantly calcium carbonate, but it sometimes also contains significant
amounts of magnesium carbonate along
with numerous other minerals. Quality specifications exist in many countries
for chemicals and materials including
lime used in the treatment of drinking water.

These specifications are intended to
assure that drinking water treatment
grade chemicals will be used and that
their addition will not concurrently
contribute significant levels of
potentially harmful contaminants to
the finished drinking water under
foreseeable use conditions.

2. Scope of the Review

 

Several issues were examined relating to the composition of drinking water that has

undergone significant treatment relevant to drinking water guidelines aimed at 

protecting and enhancing public health:

• What is the potential contribution of 
drinking water to total nutrition?
 

• What is the typical daily consumption 
of drinking water for individuals, 
considering climate, exercise, age etc.?

 

• Which substances are often found in 
drinking water that can contribute 
significantly to health and well-being?

 

• Under what conditions can drinking 
water be a significant contribution to 
the total dietary intake of certain 
beneficial substances?
 

• What conclusions can be drawn on the relationship between calcium, 
magnesium, and other trace elements in 
water and mortality from certain types of cardiovascular disease?
 

• For which substances, if any, can a case 
be made for supplementation of mineral 
content in treated reduced mineral content drinking water from the public health perspective?
 

• What is the role of fluoride in 
remineralized drinking water with respect 
to dental benefits and dental fluorosis, 
and skeletal fluorosis?

II. TOPICS EXAMINED IN THE 

MEETING
 

1. Drinking Water Consumption

It is important to understand water 
consumption patterns. The daily water 
volume ingested will also determine the consumption of any minerals that it 
contains. An individual’s daily aqueous 
fluid ingestion requirement can be said 
to roughly equate to the obligatory 
water losses plus sweat/perspiration 
losses resulting from increased physical 
exertion and climate. WHO (2003) and 
others (ILSI 2004) have reviewed water consumption and hydration needs under 
a variety of conditions. Table 2.1 
provides information on volumes of 
water required for hydration.

An assumed water intake of 2 liters per 
day for adults is commonly used by WHO 
and regulators in computing drinking 
water guidelines and standards. Physical 
exertion, especially in extreme heat, can significantly increase water requirements. 
Sweat rates can reach 3 – 4 liters per 
hour, with variations in rate depending 
upon work/exercise intensity and 
duration, age, sex, training/conditioning, 
heat acclimatization, air temperature, 
humidity, wind velocity, cloud cover and, 
clothing. The US Army has estimated 
hourly water intake in relation to heat 
categories and has also concluded that 
liquid intake should not exceed 1.03 
liters/hr or 11.35 liters/day. Persons 
under thermal and physiologic stress 
need to pay special attention to fluid 
and total salt (sodium chloride) intake, 
with salt requirements ranging from 2 
to 4 grams per day in cool 
environments to 6 to12 grams per day 
in very hot environments. 
Hyponatremia can be a fatal 
consequence of inadequate salt intake 
under those conditions.

Table 1. Volumes (liters/day) of Water Required for Hydration - Reference value estimates,

WHO 2003

Average

Conditions

Manual Labor in High

Temperature

Total Needs in

Pregnancy/Lactation

Female Adult

2.2 , 4.5 , 4.8 (pregnancy) 3.3 (lactation)

Male Adult 2.9 , 4.5

Children 1.0 , 4.5 

Humans ingest water as plain drinking 
water, water in other beverages, and water 
in food (inherent, and/or added during preparation) and they also obtain some 
water from metabolism of food. 
Approximately one third of the daily 
average fluid intake is thought to be 
derived from food. The remaining water requirement must be met from consuming 
fluids.

Availability, ambient temperature, flavor, 
flavor variety, beverage temperature, 
proximity of the beverage to the person, 
and even beverage container have all been 
shown to impact total intake. Cultural 
variations are also known to impact the 
types of beverages consumed. Obviously, 
the total daily intake of both potentially 
harmful contaminants and beneficial

elements will be directly associated with 
the total amount and type of water that is 
being consumed.

2. Drinking Water as a Source of 
Essential Minerals

Some 21 mineral elements are known or 
suspected to be essential for humans. 
This number includes four that function physiologically as anions or in anionic 
groupings {chlorine as Cl-, phosphorus 
as PO4-3, molybdenum as MoO4-2, 
fluorine as F-}, eight that function in 
their simple cationic forms {calcium (Ca+2), magnesium (Mg+2), sodium (Na+), potassium (K+), ferrous iron (Fe+2), copper (Cu+2), zinc (Zn+2), manganese (Mn+2) } and which are subject to chelation by either intact proteins or a variety of small, organic molecules; ions of two nonmetals{iodine (I) and selenium (Se)} that function as constituents of covalent compounds (e.g., iodothyronine, selenocysteine) that are formed metabolically; and ions from five additional elements: boron (B), chromium (Cr), nickel (Ni), silicon (Si), vanadium (V)} the nutritional significance of which remain to be fully elucidated. Thus, fourteen mineral elements are established as being essential for good health; these elements in combined form affect bone 
and membrane structure (Ca, P, Mg, F), water and electrolyte balance (Na, K, Cl), metabolic catalysis (Zn, Cu, Se, Mg, Mn, Mo), oxygen binding (Fe), and hormone functions (I, Cr).

Health consequences of micronutrient deficiencies include increased morbidity, mortality due to reduced immune defense systems and impaired physical and mental development.
 

Deficiencies of several mineral elements, particularly iron and iodine, are the basis 
of health problems in many parts of the world. Nearly 40% of the world’s women are estimated to be anemic due, to a great extent, to poorly bioavailable dietary iron. Low intakes of Ca, and perhaps Mg, contribute to rickets in children and osteoporosis in women worldwide. Due to inadequate diets, many children are deficient in Fe, Zn, and Cu and other micronutrients especially in developing countries. One third of the world's children fail to reach their physical and mental potentials and many are made vulnerable to infectious diseases that account for half of all child deaths. Nearly 750 million people have goiter or my edematous cretinism due to iodine deficiency, and almost 2 billion people have inadequate iodine nutrition. These nutritional deficiencies decrease worker productivity and increase the rates of disease and death in adults.
 

Many result from diets that may also
involve insufficient intakes of Cu, Cr and
B. In developed countries changing
dietary patterns such as reduced milk
consumption may predispose to

conditions like osteoporosis.
 

Drinking water supplies may contain some of these essential minerals naturally or through deliberate or incidental addition. Water supplies are highly variable in their mineral contents and, while some contribute appreciable amounts of certain minerals either due to natural conditions (e.g., Ca, Mg, Se, F, Zn), intentional additions (F), or leaching from piping (Cu), most provide lesser amounts of nutritionally - essential minerals. Many persons consume mineral waters because of the perception that they may be more healthful.
 

The enteric absorption of minerals from drinking water is determined by several factors including the intrinsic properties of particular chemical species that are present, physiological conditions of the gut environment, and exogenous factors related to the meal/diet in which the minerals are ingested. Accordingly, waterborne selenium (selenite, selenate) is passively absorbed at somewhat lower efficiencies (60-80%) than the seleno amino acids in foods (90-95%) that are actively transported across the gut.

The inorganic oxidized iron in water will be absorbed at very low is also subject to age-related declines inefficiency (Cu, Zn), early post-natal lack of regulation (Fe, Zn, Cr), adaptive increases in efficiency by receptor up-regulation during periods of deficiency (Fe, Zn, Cu, Mn, Cr), dependence on other co-present nutrients for metabolism (Se-I, Cu-Fe), and to anabolic and catabolic effects on tissue sequestration (Zn, Se, Cr).

Minerals in water are subject to most of
the same determinants of bioavailability
that affect the utilization of those minerals
in foods. For example, phytate,
phosphorus and triglycerides can each
reduce the lumenal solubility and, hence,
the absorption of calcium. Phytate and
other non-fermentable fiber components
can bind Fe, Zn, Cu and Mg, and sulfides
can bind Cu, reducing the absorption of
each. Minerals that share transporters can
be mutually inhibitory (SO3-2 vs.

SeO3-2; Ca+2 vs. Zn+2; Cd+2 vs. Zn+2;
Zn+2 vs. Cu+2). In contrast, the
bioavailability of the divalent cations
(Ca++, Fe++, Cu++, Zn++) can be
enhanced by certain chelating substances
(e.g., unidentified factors in meats,
ascorbic acid) that promote their enteric absorption, and by certain pro-biotic
factors (e.g., inulin and other fructo-oligosaccharides) that promote their hind

gut absorption. In general, poor
bioavailability can be expected of water-
borne iron consumed with plant-based
diets containing phytates and/or
polyphenols and a few promotor substances.
 

Similarly, waterborne calcium will be
poorly utilized when consumed with
oxalate-containing vegetables (amaranth,
spinach, rhubarb, beet greens, chard); and
water-born Ca, Fe, Mg, P or Zn will be
poorly utilized when consumed with
foods/diets high in unrefined,
unfermented cereal grains or high
phytate soy products. This complexation*
between calcium and oxalate in the gut
could reduce the potential for kidney
stone formation. The typical
bioavailability and occurrence of these
minerals is summarized in Table 2.
 

Note*: Complexation is the combination of individual atom groups, ions or molecules to create one large ion or molecule. One atom or ion is the focal point of the complex. This central atom contains empty electron orbitals that enable bonding with other atoms as well as unshared electrons.

The potential contributions of drinking
water to nutritional status also depend on
water consumption, which is highly
variable depending on both behavioral
factors and environmental conditions.
Individuals with the greatest relative
consumption of water include infants,
residents in hot climates, and individuals
engaged in strenuous physical activity.
 

Table 2. Typical Bioavailability and Occurrence of Nutritionally Important Minerals in Drinking Water
 

Bioavailability // Occurrence:

Moderate Amounts in Some

Supplies // Low Amounts in Most Supplies

 

High //: Se* // P

Na // K*

Cl // Mo

F // I*

B*

Moderate/Variable // :Ca* //Mn

Mg*

Cu*

Zn*

 Low // :Fe* // Cr

**sub-optimal consumption and/or prevalent deficiency in at least some countries
 

With all of these considerations in mind,
the nutrients sometimes found in drinking
water at potentially significant levels of
particular interest are:
 

• Calcium – important in bone health and possibly cardiovascular health
 

• Magnesium – important in bone and cardiovascular health
 

• Fluoride – effective in preventing dental caries
 

• Sodium – an important extracellular electrolyte, lost under conditions of excess sweat
 

• Copper – important in antioxidant function, iron utilization and cardiovascular health
 

• Selenium – important in general antioxidant function and in the immune system
 

• Potassium is important for a variety of biochemical effects but it is usually not
found in natural drinking waters at
significant levels.
 

3. Infants and Neonates

 

The needs of water and essential minerals
in infancy and childhood are increased
compared to adults in relation to body
weight. The highest intake per body
weight water volume is needed in the
neonate and it decreases with age. Special situations require additional water intake,
e.g. premature or low birth weight infants
or diarrhoeal disease. The elderly and
infirm often do not consume sufficient
water or other fluids and can become
dehydrated with significant adverse

health consequences (WHO 2003)

The WHO Global Strategy on Infant and Young Child Feeding promotes exclusive breastfeeding in the first six months of life. If this is not feasible, it may be necessary to consider feeding formula. Variable mineral content of drinking water used to reconstitute feeding formula will result in variability in the mineral content of formula milk. Some types of water may not be suitable for use in the reconstitution of infant formula due either to deficiency of appropriate minerals or to the presence of excess salts that may be harmful to infants and young children. Sodium is a good example since the requirement of infants for sodium is low.
 

Formula-fed infants are also a group at risk for excess intake of potentially toxic elements in drinking water, e.g. excess copper or lead leaching from copper or lead pipes associated with highly corrosive water. In the latter case not using ‘first draw’ water for formula preparation, by allowing the tap water to run to waste for a short time, would usually significantly reduce the metal content in the water if the lead is derived from lead-containing brass faucet fixtures or from lead soldered pipe joints. Lead services or lead pipe require other actions.
 

Remineralization/stabilization of
demineralized water for drinking water
supply should take into account the
special requirements of infants and
children, including calcium, magnesium,
and other minerals based upon regional
dietary composition.
 

III. DRINKING WATER AND

HEALTH RELATIONSHIPS
 

1. Water Hardness and Cardiovascular

Disease: Epidemiological studies of

water hardness, Ca and/or Mg, and

CVD risks

 

More than 80 observational
epidemiological studies were collected
from the worldwide literature published
since 1957 which related water
hardness and cardiovascular disease
risks (see Calderon and Monarca papers
and Table 3.1 for partial summaries).
These studies were conducted in more
than 17 countries, primarily in North
America, Europe, and Japan. Most of
the studies summarized in this report
were published in peer reviewed
English-language scientific journals,
and some were translated from eastern
European literature.
 

Most, but not all, of the studies found an inverse (protective) association between cardiovascular disease mortality and increased water hardness (measured by calcium carbonate or another hardness parameter and/or the calcium and magnesium content of water). The associations were reported in numerous countries, and by many different investigators, with different study designs. Both population and individual-based studies have observed benefits.

The most frequently reported benefit was a reduction in ischemic heart disease
mortality. The strongest epidemiologic
evidence for beneficial effects was for
drinking water magnesium concentrations;
there was also evidence - but not as strong
- for drinking water calcium
concentrations. In addition, there is
supporting evidence from experimental
and clinical investigations suggesting a
plausible mechanism of action for
calcium and magnesium. The potential significance of the epidemiological
findings is that beneficial health effects
may possibly be extended to large
population groups on a long-term basis
by simple adjustments the water quality.
 

Figure 1. Principal epidemiological studies 1979-2003
 

Principal epidemiological studies 1979 to 2003 on the association between drinking water hardness and chronic diseases

 

Drinking water hardness and/or Ca/Mg

concentrations:-

  

4. Neural tube defects

  

Ecological studies: n=3

Case-control studies: n=1

 

1. Cardiovascular diseases

  

Ecological studies: n=19

Case-control studies: n=6

Cohort studies: n=2

3. Cancer

Ecological studies: n=1

Case-control studies: n=6   
 

2. Renal stone formation

(nephrolithiasis)

Cross-sectional studies: n=2

Case-control studies: n=1

Ecological studies: n=1

Clinical trials: n=6 

5. Other diseases

(cognitive impairment,

diabetes, eczema, low birth

weight)

Case-control studies: n=1

Cross-sectional studies: n=4

Ecological studies: n=1    

Several intervention and clinical studies (which were not specifically included in this report) for magnesium and also calcium indicate that they may be effective in reducing blood pressure in hypertensive individuals. Magnesium exerts multiple cellular and molecular effects on cardiac and vascular smooth muscle cells, which could be a plausible basis to explain its protective action. Several medical treatment studies involving infusion of magnesium after a cardiac event have had mixed results, but in one example treatment of suspected myocardial infarction cases with intravenous magnesium salts reduced mortality due to arrhythmia and infarction thirty days post therapy. Other controlled human consumption studies have measured physiological differences when comparing persons on low and higher magnesium diets.
 

2. Studies of other water constituents

 

Other micronutrients and trace element nutrition studies have not been extensively examined in this review, but nutritional studies suggest that some may have an indirect or direct beneficial role associated with their presence in drinking water. However, a recently published study in Finland suggested that iron and copper in drinking water may be associated with increased risks of heart attack. On the other hand, it has been suggested that the apparent benefits associated with consumption of hard water might also be explainable as an indirect consequence of lower corrosivity compared to soft water, thus reducing human exposures to metals extracted from the pipe and fixtures. More studies are needed to better understand the possible risks and benefits of these essential and other trace elements found in water and the conditions of water exposure.

 

Principal epidemiological studies 1979 to 2003 on the association between drinking water hardness and chronic diseases:-

 

Drinking water hardness and/or Ca/Mg

concentrations

Neural tube defects

Ecological studies: n=3

Case-control studies: n=1

 

Cardiovascular diseases

 

Ecological studies: n=19

Case-control studies: n=6

Cohort studies: n=2

 

Renal stone formation

(nephrolithiasis)

Cross-sectional studies: n=2

Case-control studies: n=1

Ecological studies: n=1

Clinical trials: n=6

 

Cancer

Ecological studies: n=1

Case-control studies: n=6
 

Other diseases

(cognitive impairment,
diabetes, eczema, low birth
weight)

Case-control studies: n=1

Cross-sectional studies: n=4

Ecological studies: n=1

3. Discussion

Hard water is a dietary source of calcium
and sometimes magnesium, although the
absolute and relative concentrations will
vary greatly by source and the water
consumption levels.

Consumption of moderately hard water
containing typical amounts of calcium and magnesium may provide an important
incremental percentage of the daily dietary requirement. Inadequate total dietary intakes of calcium and magnesium are common worldwide, therefore, an incremental contribution from drinking water can be an important supplement to approach more ideal total daily intakes. It has also been suggested that hard water can reduce the losses of calcium, magnesium and other essential minerals from food during cooking. If low mineralized water were used for food and beverage production, reduced levels of Ca, Mg, and other essential elements would also occur in those products. Low intakes would occur not only because of the lower contribution of these minerals from water used in beverages, but also possibly
because of higher losses of the minerals from food products (e.g., vegetables, cereals, potatoes or meat) into water during cooking.
 

Most of the reported epidemiology studies are of the less precise ecological type, but there are also several cohort and case control studies. Based upon the studies that have been reviewed, the meeting concluded that on balance there is sufficient epidemiological and other
biological evidence to support the
hypothesis of an inverse relationship
between magnesium and possibly calcium concentrations in drinking water and
(ischemic) cardiovascular disease mortality.
 

There are no known harmful human health
effects in the general public associated
with the consumption of calcium and
magnesium within a large range, and the nutritional essentiality of calcium and
magnesium is well known. In addition,
limited but suggestive evidence exists for

benefits associated with other diseases
(stroke, renal stone formation, cognitive impairment in elderly, very low birth
weight, bone fractures among children,
pregnancy complications, hypertension,
and possibly some cancers). The
suggestion is that reintroduction of
magnesium and calcium into
demineralized water in the
remineralization process would likely
provide health benefits in consumer
populations. Adding calcium and
magnesium carbonates (as lime or

limestone) to the demineralized water is a  common water stabilization practice and is relatively inexpensive. The increased daily intake of those elements from that source does not require individual behavioural change, and it is already done as part of many water treatment processes.

Epidemiological studies in the United Kingdom, United States, Sweden, Russia, and France and research on changes in calcium/phosphorus metabolism and bone decalcification provide information about drinking water levels of calcium and magnesium (and water hardness) that may provide beneficial health effects. Several authors have suggested that reduced cardiovascular mortality and other health benefits would be associated with minimum levels of approximately 20 to 30 mg/l calcium and 10 mg/l magnesium in drinking water. The percentage of the recommended daily allowance of calcium and magnesium provided bydrinking water at these minimum levels will vary among and within countries. Thus, lower concentrations in water may be sufficient to provide health benefits in some areas, but higher levels may be beneficial in others. Overall health benefits would be dependent upon total dietary intakes and other factors in addition to water concentrations. Because the exposure-response information is limited, further analyses, and possibly additional studies, are needed to determine the levels of calcium and magnesium that may provide most favorable population benefits in each location.
 

4. Fluoride in Remineralized Drinking Water

 

Most drinking waters contain some fluoride. Fluoride is present in seawater at concentrations of about 1.2 to 1.4 mg/l, in groundwater at concentrations from nil to about 67 mg/l, and in surface waters sometimes at concentrations as low as 0.1mg/litre or less. The amount of fluoride in treated drinking water is also affected by treatment processes such as anion exchange that will remove it along with the target contaminant (e.g.arsenic). Demineralization and some other treatment processes will also remove fluoride.
 

Very high levels of excess fluoride intake cause crippling skeletal fluorosis which is almost always associated with high fluoride intake from drinking water. This is a significant irreversible health problem in parts of India, China and Africa, for example. Ingestion of excess fluoride during tooth development , particularly at the maturation stage, may also result in dental fluorosis; these effects may also be mitigated by co-exposure to some minerals such as calcium or magnesium. Mild dental fluorosis presents as barely detectable whitish surface striations in which the enamel is fully functional. As the excess intake of fluoride increases the severity of dental fluorosis also increases. Severely fluorosed enamel is more prone to wear and fracture, and may present as pitted, darkly stained and porous enamel.
 

Fluoride intake has been known for the past 50 to 60 years to play a beneficial role in dental health; there is some evidence that it may be beneficial for bone formation, but this has not been proven. The optimal drinking water concentration of fluoride for dental health is generally,between 0.5 to 1.0 mg/litre and depends upon the volume of drinking water consumed and the uptake and exposure from other sources. These values are based on epidemiological studies conducted over the past 70 years in communities in many countries with natural and added fluoride in their drinking water. In this concentration range the maximum caries preventative effect is achieved while minimizing the levels of dental fluorosis. The WHO drinking-water 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 U.S. based upon prevention of crippling skeletal fluorosis in its climate, and a guidance level of 2.0 mg/l to avoid moderate to severe dental fluorosis. The prevalence of dental and skeletal fluorosis will also be influenced by inhalation exposure to fluoride from other sources such as burning high fluoride coal (e.g. in parts of China), other dietary sources, and total water consumption. Other water factors, such as lack of calcium and magnesium may possibly also exert some influence.
 

Dental caries (tooth decay) is the result of an interaction on the tooth surface between certain bacteria in the mouth and simple sugars (e.g. sucrose) in the diet. The level of oral hygiene care and habits of the community, including the use of fluoridated toothpaste, dental treatment such as the topical application of fluoride, and consumption of fluoridated water are major factors contributing to reduction of caries incidence. Dietary sugar intake is a significant contributing tooth decay factor. Communities in which sugar intake is low
(less than approximately 15 kg per person
/year) will usually have a low risk for
dental caries, while communities in
which sugar intake is high (greater than approximately 40 kg per person/year)
will be at high risk.

Where the risk for skeletal and dental fluorosis is high as a consequence of excess fluoride intake from drinking water, fluoride levels in drinking-water should be reduced to safe levels, or a lower - fluoride source used, especially for young children, and control of significant
non-ingestion/ inhalation exposures.
Where the aggregate risk factors for
dental caries are low (and are remaining
low) consuming low fluoride water
would probably have little or no impact
on dental caries, but to guard against
possible net loss of fluoride from the
skeleton, the meeting participants felt
that consideration should be given to
maintaining a baseline level of 0.1 to
0.3 mg/l.
 

Where caries risk is high or increasing
authorities may consider addition of
fluoride to the demineralized public
water supply up to in the range of the
WHO GDWQ level of 1.5 mg/l,
preferably adjusted to water
consumption rates; however, other
factors must also be considered.
 

For example, in countries such as those in Scandinavia, where public dental
awareness is very high and alternative
vehicles for fluoride (e.g. fluoridated

toothpaste) are widely available and
widely used, a decision to not fluoridate
the water, or remove fluoride, or to supply drinking water with suboptimal levels of
fluoride would likely be of little
consequence. On the other hand in
developing and developed countries
where public dental health awareness in
some population groups (e.g. lower
income) might be much lower, water
containing either natural or added fluoride
at concentrations of 0.5 to1.0 mg/l would
be important for dental health. Some
countries use fluoridated table salt as a
means of supplementing fluoride in
deficient areas. A decision to use
demineralized water as a drinking water
source without addition of fluoride during remineralization will depend upon: the concentration of fluoride in the existing
local supply, the volume of water
consumed, the prevalence of risk factors
for dental caries (including sugar
consumption data), oral hygiene
practices and dental care, the level of
public dental health awareness, and the
presence of alternative vehicles for
fluoride intake available to the whole

population.
 

IV. CONCLUSIONS AND

RECOMMENDATIONS

 

The meeting participants concluded that:
 

• On balance, the hypothesis that
consumption of hard water is associated
with a somewhat lowered risk of CVD

was probably valid, and that magnesium
was the more likely contributor of those
benefits.

 

• Stabilization of demineralized and
corrosive drinking water should be done
where possible with additives that will
increase or reestablish calcium and
magnesium levels. The general
public and health professionals should
have access to information on the
composition of community supplies
and bottled water. Water bottlers may
also consider providing some waters
with mineral compositions that are
beneficial for population segments.

• Unless properly stabilized, demineralized
and some natural waters are corrosive to

plumbing resulting in damage to the

plumbing systems, and also in potentially increased exposure to metals such as

copper and lead. Properly stabilized water

should be provided by suppliers, and

appropriate plumbing materials should be used.

 

• There is a need for more precise data on
the impact of fluid composition and intake,

including water and other aqueous
beverages, on nutrient intake under a
broader range of physiologic and climatic

conditions for sensitive population
segments in order to more precisely
evaluate the importance of minerals in
drinking water on mineral nutrition.

• Additional studies should be conducted
on potential positive or negative health

consequences associated with
consumption of both high and low total
dissolved solids content waters in addition to consideration of water hardness.
Investigators should consider exposures to
both calcium and magnesium levels in
addition to other minerals and trace
elements that may be present in hard and
soft waters and in softened waters.
 

• Information should be provided on
methods of application of home water
softening devices so that consumers can

also have access to mineralized water for
drinking and cooking.
 

• Chemicals such as lime used in the
treatment of drinking water should
be assured to be of suitable quality for

that application so as not to contribute unacceptable amounts of potentially
harmful chemicals to the finished water.
 

• Investigators may take advantage of
natural experiments (communities
changing water sources and treatment)

to conduct population intervention studies
to evaluate potential health impacts. For
example, studies could compare
communities before and after changing
source waters, or the introduction of
treatment technologies that significantly
change water composition.
 

• Water utilities are encouraged to
periodically analyse their waters for
calcium, magnesium, and trace elements.

This would be helpful in assessing trends
and conducting future epidemiologic studies.

• Studies on the mineral nutritional content
and adequacy of world diets should be
conducted so that adequacies and

inadequacies can be documented and
possibly mitigated.

 

 

• Studies should evaluate a number of

potentially relevant health outcomes

(e.g., renal stone formation, CVD*,

hypertension incidence, osteoporosis,

stroke, mineral balance, mineral

nutritional deficiencies). Exposure
assessments should include analyses for
calcium, magnesium, and trace elements.

NOTE*- Cardiovascular disease (CVD)
is a class of diseases that involve the heart
or blood vessels. Cardiovascular disease
includes coronary artery diseases (CAD)
such as angina and myocardial infarction (commonly known as a heart attack).
 

• Studies should evaluate the issue of
whether there are adverse health
consequences associated with
consumption soft corrosive water due to

extraction of metals from pipe.

There should also be additional studies to determine whether and how softened
waters differ in that respect from soft waters.

• Clinical trials of people at high risk of
heart attacks and other illnesses such as osteoporosis, should be conducted to
assess the potential benefits of mineral

supplementation. Results of previous
studies have been inconsistent.

• In the revisions of the Guidelines for
Drinking-water Quality, WHO should
consider the beneficial roles of nutrient

minerals including water hardness
characteristics.

 

• This subject is of such potential general
public health significance that a detailed
state-of-the-art review should be

prepared prior to consideration in the next
revision of the WHO Guidelines for
Drinking Water Quality.

References

1. Calderon. R. and G. Craun, Water Hardness and Cardiovascular Disease: A Review of the Epidemiological Studies 1957-78.

2. Cotruvo, J.A., Desalination Guideline Development for Drinking Water.

3. Craun, G.F., and R. Calderon, How to Interpret Epidemiological Associations.

4. Donohue, J.M., Abernathy, C.O., Lassovszky, P. and G Hallberg. The Contribution of Drinking Water to Total Dietary Intakes of Selected Trace Mineral Nutrients in the USA.

5. Frost, F., Studies of Minerals and Cardiac Health in Selected Populations.

6. Grandjean, A., Water Requirements, Impinging Factors and Recommended Intakes. ILSI

North America, Hydration: Fluids for Life, 2004, Monograph Series.

7. Klevay, M. and G.F. Combs Jr., Mineral Elements Related to Cardiovascular Health.

8. Kozisek, F., Health Risks from Drinking Demineralized Water.

9. Lennon, M.A., Whelton, H., O’Mullane, D. and L. Ekstrand, Fluoride.

10. Monarca, S., Zerbini, I. and F. Donato, Drinking Water Hardness and Cardiovascular

Diseases: A Review of Epidemiological Studies 1979-2004.

11. Olivares, M. and R. Uauy, Nutrient Minerals in Drinking Water: Overview.

12. Ong, C.N., Minerals from Drinking Water: Bioavailability for Various World Populations

and Health Implications.

13. Sievers, E., Nutrient Minerals in Drinking Water: Implications for the Nutrition of Infants

and Young Children.

14. WHO 1999, Fluoride in Drinking Water. WHO/WSH/Draft99.4, Geneva 1999.

15. WHO 2003, Howard G. and J. Bartram, Domestic Water Quantity, Service Level and Health, WHO/SDE/WSH/3.02.

16. WHO 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/SDE/WSH/04.01.