1. Growth: Food is essential for growth. Without food a living organism will stop growing. The living cells in our body multiply after getting nourishment from the food we eat. Insufficient or a wrong type of food does not help healthy growth.
2. Repair: Living organisms sometimes damage their parts by accident. Constant work also causes wear and tear of the body parts. If we get a wound or cut, it heals up after some time. If we damage our skin due to some burn etc., it regains its shape in due course. The body needs food for all these functions.
3. Energy: We spend our energy when we do work. That is why after doing considerable work, we get tired. We then need food and rest to regain the lost energy. If we do not get food, we would become weak.
4. Protection from Diseases: We need to protect our body from diseases and keep it healthy. For this, we need vitamins and mineral salts in our food. Vitamins neither provide energy nor do they repair or replace the worn-out parts. But they are essential for our proper health.