Water: Functions and Role

Water: Functions and Role

Water is essential for life. In fact, one can survive without food for weeks but not without water. Water is a macronutrient made of two elements hydrogen and oxygen. A molecule of water contains two atoms of hydrogen and one atom of oxygen. In other words the ratio is 2:1. Remember water is an inorganic compound. You would have noticed that water has earlier been referred to as a food. This is because water in the form in which we consume it contains other nutrients like sodium and potassium which belong to the mineral category.


What role does water play in our body?

Many of the functions of water are self-evident. 

  • Water is the major component of our body. It makes up approximately 60 percent of the total weight of an adult and almost 75 per cent in the case of theb infant. It serves as the major and essential component of all cells and tissue though the amount of water present in different body tissues varies.

  • Water is the medium of all body fluids including blood, saliva, digestive juices urjne, faeces, sweat or perspiration.

  • Water plays an important role in the regulation of body temperature. Under normal circumstances your body temperature is maintained at 98.4° F or 37° C. You know that heat is produced in the body by the burning of carbohydrates, fats and proteins. Water helps to distribute this heat throughout the body. Some amount of water is lost from the

  • body by evaporation and cools it down. This is because the water uses the body heat to evaporate. Thus, extra heat from the body is lost and body temperature is maintained.

  • Water is a universal solvent. This means it dissolves a variety of substances including all the products of digestion and carries them to various parts of the body via blood. Similarly, it helps in the removal of the waste products from the body. This property of water makes it essential for all the chemical reactions taking place in the body.

  • Water bathes the body cells and keeps them moist. Hence it acts as a lubricant. Water present in saliva and other digestive juices helps in the passage of food down the digestive tract. It is also an important lubricant for the joints. Water does not undergo any digestive change in the body and is absorbed as such.


Our body gets water mainly by:

  • The ingestion of water in the form of liquids: This includes water which we drink daily as such or part of beverages like tea, coffee, fruit juices and aerated drinks.

  • The ingestion of water in the form of solid foods: Water is present in various foodstuffs in hidden or invisible forms. The water content of foods varies widely. Table gives water (moisture) content of some of the foodstuffs. It is vital that the water we drink is safe and free from germs causing water borne diseases such as diarrhoea, dysentery, and cholera. Clean and safe drinking water is absolutely necessary.

Moisture content of some Foodstuff
Foodstuff Moisture content  (g)












Cow's milk




Rice (raw, milled)




Bengal gram


  • Water formed in the body from the metabolism of nutrients. Some amount of water is formed in the body during the various chemical reactions involved in the metabolism of carbohydrates, as you have studied earlier. The reactions involved in fat and proteih metabolism also contribute water to the body.

Thus the total water available to the body is obtained through these three sources  i.e. drinking water and beverages, foods and the metabolism of nutrients in the body.

During the course of utilization of water for various body processes some amount of water is also lost from the body through the kidneys, skin, lungs and digestive tract.
A significant amount of water is lost through the skin in sweat or perspiration. Water is lost from the kidneys in the form of urine. A small amount of water is also lost from the digestive tract in saliva and faeces. The air we breathe out from the lungs also contains some amount of water. Normally the body maintains balance between intake of water i.e. ingestion and loss of water from the body i.e. excretion. This is termed water balance.

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