WATER AND ELECTROLYTE BALANCE

KOMAL OJHA
PH.D 1st year
WATER AND ELECTROLYTE BALANCE

Content
 Distribution
 Functions
 Sources
 Requirements
 Water intake and loss
 Water balance
 Water intake regulation
 Water excretion regulation
 Mechanism of water balance
 Water imbalance
 electrolytes balance
 References

Water
• Water is considered as the most important nutrient for the body. It forms the
greatest component of the human body, making up 50% to 60% of body
weight. Lean muscle tissue contains about 73% water.
• Fat tissue is about 20% water. Thus as fat content increases in the body,
total body water content declines towards 50%. Water – the most versatile
medium for all kinds of chemical reactions constitutes the major portion of
our bodies.
• Without water, the life processes would cease in a matter of days.
• The water content of soft tissues ranges from 70 to 80 per cent while that of
bone about 20 per cent.

Distribution
The body water can be visualised to be distributed mainly in two compartments.
• Intracellular fluid - a fluid present in the cells.
• Extracellular fluid - a fluid present outside the cells.
The extra cellular water is further sub divided into
• water in blood plasma (about 4 per cent);
• interstitial water – water in tissue spaces (9 per cent) and
• Lymph in the lymphatic vessels (7 per cent).

Functions
Of all the nutrients, water is the most critical as its absence proves lethal within a
few days. Water's importance in the human body can be loosely categorized into
four basic functions: transportation vehicle, medium for chemical reactions,
lubricant/shock absorber, and temperature regulator.
• Regulates body temperature
• Moistens tissues in the eyes, nose and mouth
• Protects body organs and tissues
• Carries nutrients and oxygen to cells
• Lubricates joints
• Lessens burden the on kidneys and liver by flushing out waste products
• Helps dissolve minerals and nutrients to make them accessible to your body

Sources
Most of the requirement of the water is met by drinking as such. Part of the requirements is
met by the foods consumed and water used in cooking and the beverages consumed. A
2000kcal balance diet may provide 500 to 800 ml of water.
Metabolic water
It also contributes to the source of water. Water, in addition to C02 and energy is an end
product of combustion of CHO, fat, and protein. Oxidation of 100g each of fat, CHO, and
protein yields 107, 55 and 41g of water, respectively. Water derived through metabolism is
called metabolic water. Table 2. water content of foods
foodstuff Amount g/100g
Ash gourd 96.5
Water melon 95.8
Tomato 94
Spinach 92.1
Milk 87.5

Requirements
The requirement of water depends on a person’s age, weight, and the life style
and the climate in which he is living.
Table 1. Fluid Requirement per kg of body weight
Group Fluid ml/kg
Infants 110
10 yr old children 40
Young adults 40
Older adults 30
Elderly adults (>65 Yrs)n 25
Adults (by environments temperature)
22.2°C 22
37.8°C 38

Water intake andloss
Loss of water from the body is continuous. The body loses water
• via kidney as urine;
• via the skin in the form of insensible perspiration and as sweat;
• via the lungs in the expired air;
• to a small extent via the large intestines in the faeces and
• through milk during lactation. Water is taken in food and also as drinking water.
In addition, water is formed in the tissues by the oxidation of hydrogen released during fat, carbohydrate
and protein metabolism.
Water intake and source of body water: Water is taken as drinking water, about 1500 ml (in temperate
climate), through food, 1000 ml; and from oxidation of carbohydrates, fats and proteins in tissues, 300 ml.
Water loss: The body loses water through urine, about 1500 ml; via skin 800 ml; via lungs 400 ml and in
faeces 100 ml. In a normal individual, the water intake is approximately equal to water lost from the body
and thus the water balance of the body is maintained fairly constant.

Water Balance
Water balance refers to the balance between the amount
of water consumed and the amount of water excreted. For optimal
functioning of the body, it is essential that the water content of the body
should be maintained constant. Body fluids contain solutes (chemical
compounds that are soluble in water), which separate into charged
particles, or ions, when dissolved in water. Intracellular fluids are high
in potassium and phosphate ions, while interstitial fluids are high
in sodium and chloride ions. These ions help to maintain the amount of
fluids both within and outside the cells. Water molecules follow the
solutes moving across cell membranes from a lower to higher solute
concentration to maintain homeostasis.

Water Intake Regulation
• When there is excessive loss of water from the body, the
concentration of solutes in the blood becomes too high and the
solutes attract water from the salivary glands, making the mouth dry
and causing a person to feel thirsty.
• Heat, intense physical activity (profuse sweating), diarrhoea,
vomiting, and excessive urination can all cause excessive fluid loss.
A runner can lose upto six cups of fluid in an hour through sweat. If
the replenishment of water is not adequate, a state of dehydration
can occur. Mild dehydration occurs with a loss of 5 percent or less
of a person's bodily fluids, moderate dehydration is a loss of 5 to 10
percent of a person's bodily fluids, and severe dehydration is a loss
of 10 to 15 percent of fluids. Severe dehydration can cause death.

Water Excretion Regulation
• The brain and kidneys regulate the amount of water excreted by the body. When the
blood volume is low, the concentration of solutes in the blood is high. The brain
responds to this situation by stimulating the pituitary gland to release a hormone
known as Anti diuretic hormone (ADH), which signals the kidneys to reabsorb and
recirculate water. When the individual needs more water, the kidneys will excrete
less and even reabsorb some.
• When excessive fluid loss occurs, the blood volume, as well as blood
pressure decreases. The kidneys respond by secreting an enzyme called rennin.
Rennin activates the blood protein angiotensinogen to convert to angiotensin, which
causes the blood vessels to constrict and blood pressure to rise. Angiotensin also
activates the adrenal glands to release a hormone called aldosterone. Aldosterone
causes the kidneys to retain sodium and water. When the body needs water, less is
excreted and more is retained.

Mechanism of water balance
• In the body, several mechanisms work together to maintain water balance. One of the most
important is thirst. When the body needs water, nerve centers deep within the brain are stimulated,
resulting in the sensation of thirst. The sensation becomes stronger as the body's need
for water increases, motivating a person to drink the needed fluids. When the body has excess water,
thirst is suppressed.
• Another mechanism for maintaining water balance involves the pituitary gland (located at the base of
the brain) and the kidneys. When the body is low in water, the pituitary gland secretes antidiuretic
hormone (also called vasopressin) into the bloodstream. Antidiuretic hormone stimulates the kidneys
to conserve water and excrete less urine. When the body has excess water, the pituitary gland
secretes little antidiuretic hormone, enabling the kidneys to excrete excess water as urine.
• The body can move water from one area to another as needed. When water loss is severe, the
amount of water in the bloodstream decreases, so the body moves water from inside the cells to the
bloodstream until it can be replaced through increased intake of fluids. When the body has
excess water, the amount of water in the bloodstream increases, so the body moves water from the
bloodstream into and around the cells. In this way, blood volume and blood pressure can be kept
relatively constant.

Water imbalance
Too much water – whatever amount the kidneys are unable to excrete – can be
toxic, but an excessive amount would have to approach many liters each day. Most
people have little risk of drinking too much water, but problems do accompany
some disease states and mental disorders. When water exceeds the kidney’s
capacity to excrete, blurred vision is one resulting symptom.
• Water Intoxication
Water intoxication occurs when there is too much fluid in the body. Excess fluid
may collect in body tissues, particularly in the feet and legs resulting in a
condition called oedema. Excess consumption of fluids, as well as kidney
disorders that reduce urine output, may contribute to water intoxication. The
symptoms of water intoxication are confusion, convulsions, and, in extreme
cases, death.

Cont…..
• Dehydration
Dehydration of the body results when water is not taken in adequate
amounts to make up the water loss. Dehydration occurs rapidly in
severe diarrhea and vomiting in infants and children. Some clinical
signs of dehydration include dry skin, less frequent
urination, fatigue, light-headedness, dark-colored urine, dry mouth,
and lack of skin elasticity. Often, increased fluid intake and
replacement of lost electrolytes are sufficient oral rehydration
therapy for mild dehydration. In cases of severe dehydration, it may
be necessary to hospitalize the person and restore fluid balance
through intravenous fluid replacement.

Electrolyte balance
Electrolytes are the chemicals dissolved in the body
fluid. Sodium and potassium are two of the electrolytes essential for
proper body function. Several foods that we eat provide these
electrolytes, but often they are not in the correct proportion. Sodium
chloride is found mostly in extracellular fluid, while potassium and
phosphate are the main ions in the intracellular fluid.
1. Sodium
2. Potassium
3. Chloride

Sodium
Sodium is the major positive ion of the extracellular fluid. It is important for
maintaining
– Fluid balance
– Muscle irritability
– Acid-base balance
– Conducting nerve impulses and osmotic pressure.
When combined with chloride, the resulting substance is sodium chloride or table
salt. Excess sodium (such as that obtained from dietary sources) is excreted in the
urine. Fluid balance throughout the body depends partly on varied sodium
concentrations among the water-containing compartments in the body. In a normal
man the extracellular fluids contain 2175 mEq. of Na and intracellular fluids about
375 mEq. In addition about 900 mEq of Na is present in the bones, making a total of
about 3450 mEq. (200g. of Nacl) in the whole body.

Cont….
Intake of sodium:
Dietary intake of sodium is very variable. Most normal people ingest 5 to 20g.
NaCl/day, corresponding to 70 to 350 mEq. of Na. The food as served contains about
200 mEq. Na/day. In general, foods as such, contain relatively little sodium, but large
amounts may be added in cooking. In most forms of processing and preservation, salt is
added. Butter and many other foods are commonly salted in preparation.
Output of sodium:
Sodium is lost through sweat, faeces and urine. In normal conditions, the losses
through the first two routes are minimal, and a bulk of it is lost in urine. The sweat
loss is variable and can be decreased by adaptation to heat. Most of the daily output
of sodium is in the urine which usually contains 100-150mEq./24 hrs., and reflects
the dietary intake.

Cont..
Table : Sodium balance in man (mmoles/day)
a---- Variable with environmental temperature and humidity and physical activity
b---- Negligible in basal state but can be high in diarrhoeal diseases.
Source Sodium input Source Sodium output
Food and water 100-400
Sweat
Faeces
Urine
a
b
Total 100-400 100-400
Men doing hard work in hot humid climates, as in mines suffer from heat cramps, i.e.,
intense and painful contractions of skeletal muscle. This is due to NaCl deficiency
caused by loss of NaCl from the body by excessive sweating.

Cont….
• Increased sodium level in the blood (hypernatremia) occurs whenever
there is excess sodium in relation to water. There are numerous causes of
hypernatremia; which include kidney disease, too little water intake, and
loss of water due to diarrhea and/or vomiting.
• A decreased concentration of sodium (hyponatremia) occurs whenever
there is a relative increase in the amount of body water relative to sodium.
This occurs in some diseases of the liver and kidney, in patients with
congestive heart failure, in burn victims etc.
A normal blood sodium level is 135 - 145 milliEquivalents/liter (mEq/L), or in
international units, 135 - 145 millimoles/liter (mmol/L).

Potassium
Potassium performs functions similar to those of sodium, except that it is the main positive
ion found inside(intracellular), cells. Potassium is vital to fluid balance and nerve
transmission. The potassium content of foodstuffs is very variable.
• Intake of potassium:
The intake of K+ is largely from diet with some contribution from drinking water.
Natural diets provide from 50 to 150 mEq. K/day. Most of the common foods contain
moderate amounts. Cereals (including rice and wheat), cheese, eggs, fats and almost all
fresh fruits contain less than 8 mEq. K/100g. and have been used in planning low
potassium diets.
 a and b – 5% loss through sweat and faeces
Source Sodium input Source Sodium output
Food and water 100-400
Sweat
Faeces
Urine
a
b
Total 100-400 100-400

Cont….
Output of potassium:
Excretion of potassium is through sweat, faeces and urine, Urinary excretion alone
accounts for 95% of the total intake. The output of potassium in the urine closely
reflects the dietary intake. The adreno- cortical hormones cause increased potassium
excretion in the urine. Excessive production of aldosterone causes large losses of
potassium in the urine and consequent deficiency in the cells and a low level in the
blood.
• Increased potassium concentration is known as hyperkalemia. Since potassium
is normally excreted by the kidneys, disorders that decrease the function of the
kidneys can result in hyperkalemia. Certain medications may also predispose an
individual to hyperkalemia.
• Hypokalemia, or decreased potassium, can arise due to kidney diseases;
excessive loss due to heavy sweating, vomiting, or diarrhea, eating disorders,
certain medications, or other causes.

Chloride (Cl-)
• Chloride is the major negative ion of extracellular fluid. Sea water has almost the same
concentration of chloride ion as human body fluids. Chloride also plays a role in helping
the body maintain a normal balance of fluids.
• The important functions of chloride are maintenance of ECF acid-base balance and
osmotic pressure. It is also essential for the secretion of hydrochloric acid in the
stomach. The balance of chloride ion (Cl-) is closely regulated by the body. Significant
increases or decreases in chloride can have deleterious or even fatal consequences.
• The total body chloride content is about 2150 mmoles in a 60 kg man.
• Increased level of chloride (hyperchloremia): may be seen in diarrhoea, certain kidney
diseases, and sometimes in over activity of the parathyroid glands.
• Decreased chloride level (hypochloremia): Chloride is normally lost in the urine,
sweat, and stomach secretions. Excessive loss can occur from heavy sweating, vomiting,
and adrenal gland and kidney disease.
The normal range for serum chloride is 98 - 108 mmol/L.

References
• Gordon Wardlaw Gordon M. & Insel Paul M., 1992, Contemporary Nutrition,
Mosby year Book, Boston p-p 293-298.
• Swaminathan, M. 1997, Essentials of Food and Nutrition, vol I Second edition,
BAPPCO, Bangalore.p-p 432-437.
• Bamji, M. S, Prahlad Rao.N and Vinodini Reddy,(2003), Text book of Human
Nutrition, Oxford & IBH Publishing Co. Pvt. Ltd, New Delhi pp 104-110.
• Davidson. S.S. and Passmore R. (1966), Human Nutrition and Dietetics, the
Williams and Wilkins Co. pp 134-143.
• http://www.icmr.nic.in/ijmr/2009/november/1126.pdf
• http://www.8sxe.com/html/Diet---Nutrition/200907/12-511.html

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