Nutrition includes all those processes of a living being whereby it takes food, digests it, and utilizes the digested materials for (i) its survival, (ii) growth, and (iii) repair of worn-out parts the body. Digested and assimilated materials become the food for cells.

Nutrition is required for the following purposes.

1. Growth:

Body cells multiply regularly. They increase in size also. For these processes and to replace damaged and worn-out tissues, new protoplasm is continuously required. Food helps in the formation of new protoplasm in the body.

2. Release of Energy:

Energy is required for performing various life process like ingestion, digestion, absorption, movement, co-ordination, secretion, circulation, respiration, etc. energy required for these processes is released by the oxidation of food in the protoplasm.

3. Formation of Organic substance:

Many organic substances like enzymes and hormones are required by the living beings. These are produced from the raw materials provided by food.

4. Regulating Metabolic Processes:


Food is required by the organisms for various other metabolic activities. For maintaining and repairing various parts, the food provides basic raw materials.

5. Giving resistance:

Food is also helpful in building up the resistance against diseases. Nutrition is classified into two types-autotrophic and heterotrophic.