Protein is essential for the body because it plays several critical roles:

1. Building and Repairing Tissues: Protein helps build muscles, skin, organs, and other tissues. It also repairs damaged tissues after injury or exercise.

2. Enzyme Production: Many enzymes in the body are proteins, which help carry out vital chemical reactions such as digestion and energy production.

3. Hormone Regulation: Some hormones, like insulin and growth hormone, are made of protein and help regulate various body functions.

4. Immune Function: Proteins help form antibodies, which protect the body from infections and illnesses.

5. Transport and Storage: Proteins like hemoglobin transport oxygen in the blood, while others help store nutrients.

6. Energy Source: While not the body's primary fuel, protein can be used for energy when carbohydrates and fats are insufficient.