Which of the following is considered a macronutrient?

Protein is classified as a macronutrient because it is one of the essential nutrients required by the body in larger amounts to support various physiological functions. Macronutrients include proteins, carbohydrates, and fats, and they provide the energy needed for daily activities as well as the building blocks for growth, repair, and maintenance of tissues.

In contrast, Vitamin C and Iron are considered micronutrients. Micronutrients are required in smaller quantities but are still critical for health, playing vital roles in metabolic processes and the functioning of enzymes. Calcium, while also important, is also categorized as a micronutrient, even though it is needed in larger amounts than many other micronutrients, because it does not provide energy but is crucial for bone health and various bodily functions. Thus, protein is uniquely significant as a macronutrient that contributes both energy and structural functions in the body.