Sodium: Functions, Food sources, Absorption and excretion

Sodium: Functions, Food sources, Absorption and excretion

An adult body contains approximately 120g of sodium. Most of this is present in the extracellular fluid. Extracellular fluid refers to the fluid outside the cell just as intracellular fluid refers to fluid inside the cell. One example of extracellular fluid is blood plasma. You may remember that blood has two parts- cells and plasma. The term plasma refers to the fluid part of the blood.

Let us now learn what role sodium plays in our body.

( ) Potassium is mainly present in the fluid inside the cell (Intracellular), ( x ) Sodium and ( O ) Chloride are present mainly in the fluid outside the cell (Extracellular)


Some of the important functions of sodium are listed here:

  • Regulating the balance of extracellular and intracelluler fluid: Sodium, the principal mineral in the extracellular fluid, is responsible for maintaining the fluid balance. By fluid balance we mean the process of maintaining a balance between the fluid present within the cells (intracellular) and that circulating outside the cells (extracellular). Sodium along- with potassium (another mineral) helps to maintain this balance.

  • Regulating the alkalinity and acidity of the body fluids: Sodium tends to make the body fluids alkaline. Another mineral namely chloride present in the body fluids tends to make them acidic. Sodium combines with chloride in the fluid and together they help maintain the balance between the alkalinity and acidity of the body fluids.

  • Aiding in the passage of messages from one nerve cell to another.

  • Aiding the contraction of muscles and

  • Regulating the passage of substances into and out of the cell.

Food sources

Do you know what items in our diet provide maximum sodium? You are familiar with common table salt which is nothing but sodium chloride. Common table salt is the principal source of sodium in our diet. One teaspoon of salt provides almost 2000mg sodium. Other rich sources of sodium include milk, egg white, meat, poultry, fish among the animal foods and green leafy vegetables (such as spinach, fenugreek leaves) and pulses among the plant sources.

Absorption and excretion

Sodium ingested 1st readily absorbed by the digestive tract and used for various body functions. The excess amount of sodium over and above body needs is lost from the body through urine, sweat, and faeces. Sodium losses are high whenever we sweat more as in hot weather. Any disease condition in which water is lost from the body also causes excessive sodium loss. A common example is diarrhoea i.e. loose motions. Excessive sodium loss is not good as it affects the fluid balance of the body. This requires special attention. Intake of fluids and salt should be increased during such times so as to make up for the loss. The major regulation of the amount of sodium in the body is done by the kidneys by varying the total amount of urine excreted. When intake of sodium increases, excretion increases and when intake decreases, excretion decreases. This process helps to keep the body concentration of sodium within normal limits.

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