Which of the following nutrients is essential for muscle building and repair?

Proteins are essential for muscle building and repair due to their role as the body's building blocks. They are made up of amino acids, which are crucial for synthesizing new muscle tissue after exercise or injury. When you engage in resistance training or any form of physical activity, muscle fibers undergo micro-tears. Proteins help repair these tears, leading to muscle growth and recovery.

While fats and carbohydrates also play important roles in overall health and energy supply, they do not directly contribute to muscle repair and synthesis in the same way that proteins do. Fats are vital for hormone production and energy, while carbohydrates provide a quick energy source for high-intensity activities, but they aren't involved in building muscle tissue. Vitamins, on the other hand, are essential for various bodily functions but do not provide the structural components needed for muscle repair and growth. Hence, proteins are uniquely important when it comes to muscle building and repair.