Body building block is a term used to describe the essential nutrient PROTEIN. PROTEIN is a macronutrient that is necessary for the growth and repair of cells in the body. It is also important for the production of hormones, enzymes, and other body chemicals. PROTEIN is found in many foods such as meat, fish, eggs, dairy products, legumes, nuts, and seeds. Eating enough PROTEIN is important for muscle growth and maintenance, as well as for overall health.