The process of converting food into energy-giving substances is called digestion. It involves the breakdown of complex food molecules into simpler forms that can be absorbed and utilized by the body. Digestion occurs in the digestive system, which includes the alimentary canal and associated digestive glands.

Process of converting food into energy-giving substances:
The process of converting food into energy-giving substances is known as digestion. It is a complex process that involves breaking down food into smaller molecules that can be absorbed and utilized by the body for energy.

Stages of digestion:
- Ingestion: Food is taken into the mouth and broken down into smaller pieces by chewing.
- Digestion: Enzymes and acids in the stomach break down food into smaller molecules.
- Absorption: Nutrients are absorbed into the bloodstream through the walls of the intestines.
- Assimilation: Nutrients are transported to cells throughout the body where they are used for energy production.

Role of digestive system:
The digestive system plays a crucial role in the process of converting food into energy-giving substances. It consists of various organs such as the mouth, stomach, intestines, and liver, each with specific functions in breaking down food and extracting nutrients.

Importance of digestion:
Proper digestion is essential for maintaining overall health and well-being. It ensures that the body receives the necessary nutrients and energy to function optimally. Any disruptions in the digestive process can lead to various health issues such as nutrient deficiencies and digestive disorders.
In conclusion, digestion is a vital process that converts food into energy-giving substances that are essential for the body's functioning. Proper digestion ensures that the body receives the nutrients it needs to thrive and maintain optimal health.