2. • Water is the most essential constituent of our body. It accounts for 55-70% of our
total body weight.
• Men have a higher proportion of water in their body as compared to women.
• Lean individuals have more water than obese, and infants and children have a
greater proportion of water than adults.
• The body fluid is distributed among two major compartments.
1) The extracellular fluid or water present outside the cells in the interstitial space
and blood plasma.
2) The intracellular fluid or the water present inside the cells.
• Considering an average of 60% of body weight contributed by water, an adult
weighing 70kg has a total body water of 42 litres of which 28 litres is intracellular
and 14 litres is extracellular.
• Of the 14 litres, 11 litres is present as interstitial fluid and 3 litres as plasma.
3. • Water present in the body is never plain water but has electrolytes dissolved in it.
similarly, when the body loses water, it loses electrolytes as well.
• Sodium is the principal electrolyte of the extracellular fluid while potassium is
predominant in the intracellular spaces.
• The normal concentration of ions in the intracellular and extracellular fluids needs
to be maintained at all times.
• This concentration of ions is preserved by a balance between the intake of water
and the output or loss of body water.
• Functions:-
• Water quenches thirst and is the most refreshing and cooling of all liquids.
• It is a structural component of all cells. In the bone, water is tightly bound.
• Water is the medium in which all chemical reactions take place.
• It is an essential component of all body fluids such as blood, lymph, bile, digestive
juice, and urine.
4. • It acts as a lubricant and helps food to be swallowed and digested food to pass
through the gastro intestinal tract.
• It acts as a solvents for the products of digestion and helps in transporting these
products to different tissues.
• Water regulates body temperature by taking up and distributing heat produced in
cells when metabolic reactions take place.
Daily intake of water:-
Apart from the water we drink during the day to relive thirst between and during
meals, there are three major sources of water.
Beverages and liquid foods:- hot and cold beverages such as tea, coffee, milk
shakes, fruit juices, and soups are largely made up of water. Both stimulating
beverages and refreshing beverages are important sources of water and nutrients.
Water content of solid foods:- Another important source of water is fruits,
vegetables, and the water used for cooking food. Solid foods contain varying
percentages of water.
5. • The water consumed from beverages and solid food amounts to 2100ml/day
approximately.
• Metabolic water:- it is synthesized in the body as result of oxidation of fat,
proteins and carbohydrates, adding to about 200ml/day.
• Oxidation of 100g fat 107ml water
• 100g protein 41ml water
• 100g carbohydrates 56ml water
• The intake of fluid varies among different people and also varies according to the
climate, habits, and physical activity on a day-to-day.
6. DAILY LOSS OF BODY WATER
• insensible water loss:- it is the loss of water we are not consciously aware of even
though it occurs continuously in all living beings. It includes
1) Continuous loss of fluid by evaporation from the skin, which occurs
independently of sweating (this loss by diffusion through the skin is about 300-
400ml/day) , and
2) insensible water loss through the respiratory tract, which is about 300-
400ml/day (this loss of water is greater in cold weather.)
• Water loss through sweat:- the extent of water loss through perspiration or
sweat largely depends on physical activity and environmental temperature. The
volume of sweat secreted is normally about 100ml/day but could increase to a few
litres in very hot weather or during heavy exercise.
• Water loss in urine:- this is the most important mechanism by which the body
maintains a balance between fluid intake and output as well as electrolyte
homeostasis. ( maintain relatively constant internal environment is called) water,
body temperature, chemical levels.
7. • urine volume can be as low as 0.5 litre/day in a dehydrated person or as high as
20 litres/day in a person who has been drinking tremendous amount of fluid.
• The rate of filtration of water in the normal kidney is about 125ml/minute or
approximately 180 litres daily for an adult. About 99% of the water filtered is
reabsorbed into the blood while 500-2000 ml is excreted as urine.
• Water loss in faeces:- only a small amount of water (100ml/day) is normally lost
in faeces.
• If there is a diarrhoea or vomiting, fluid losses may be large and cause
dehydration.
• Water balance:-
• Deficiency of water
• Excessive loss of water could take place due to diarrhoea, vomiting, fever,
excessive perspiration, strenuous exercise, and uncontrolled diabetes mellitus. It
can result in dehydration. Dehydration can be classified as
8. Mild <5% fluid loss
Moderate 5-15% fluid loss
Severe 15-20% fluid loss
A 20% loss of fluid from the body can be dangerous.
A dehydrated person feels thirsty, has a dry mouth, dry eyes, and may feel restless,
irritable, or even lethargic or unconscious in severe cases.
A dehydrated person is usually managed by Oral Rehydration Therapy (ORT). The
WHO recommends Oral Rehydration Salts (ORS) that are to be dissolved in a
1litre of water. This is to be sipped till hydration returns to normal.
ORS Formula
Ingredients Amount in Grams
Sodium chloride (Nacl) 3.5
Trisodium citrate dehydrated 2.9
Pottasium chloride 1.5
Glucose anhydrous 20
water 1 litre
9. • Oral rehydration salts are most often presecribed in cases of diarrhoea. Glucose
present in ORS, enhance the absorption of salt.
• Apart from ORS,ORT also includes any of the following
• Sugar and salt solution (40g sucrose + 4g NaCl in litre of water)
• Rice water with salt(50g rice + 4g salt in 1 litre water)
• Plain water, lemon water, coconut water, thin soups, or dal water may also be
given along with ORT.
• If vomiting is severe, intravenous fluids such as normal saline (0.9%NaCl) and
dextrose need to be administered. When the body loses fluids, it loses both water
and electrolytes, hence ORS or Dextrose Normal Saline (DNS) is given.
Dehydration cannot be treated by giving pure water only.
• Daily Requirement:-
• A minimum of six to eight glass of water is recommended to enable the body to
perform optimally and keep one active and refreshed throughout the day. It should
be consumed at regular intervals so that the body is always well dehydrated.