Protein is an essential nutrient for building and repairing muscle tissue. When you exercise, you create tiny micro-tears in your muscle fibers, and protein is necessary for repairing and rebuilding those fibers, which can lead to muscle growth and increased strength over time.

There are many sources of protein that can be incorporated into a muscle-building diet. Some examples include:

1. Lean meats like chicken, turkey, and fish
2. Eggs
3. Dairy products like milk, yogurt, and cheese
4. Plant-based proteins like beans, lentils, nuts, and seeds
5. Protein supplements like whey protein, casein protein, and plant-based protein powders

It’s important to note that while protein is essential for muscle building, it’s not the only factor. A balanced diet that includes carbohydrates, healthy fats, and plenty of fruits and vegetables is also important for overall health and fitness. Additionally, regular strength training and adequate rest and recovery are crucial for building muscle.