Which nutrient is present in foods referred to as body-building foods?

Proteins are a major component of our muscles, bones, skin, organs, nails, and hair. 

They are large biomolecules and are made up of long amino acid chains They are important components of the food we eat. Foods containing proteins are called body-building food. They help our body build and repair tissues and cells, help in growth, and aid the immune system fight viral infections.