What does protein in the diet primarily contribute to the body's chemistry?

• A. Calories
• B. Fat
• C. Nitrogen
• D. Minerals

Answer: (C)

Proteins primarily contribute nitrogen to the body's chemistry. Dietary protein supplies amino acids that contain amino groups with nitrogen, and the body uses this nitrogen to build and repair tissues and to form nitrogen-containing molecules such as enzymes, hormones, and nucleotides. While protein can provide energy, its standout chemical contribution compared with carbohydrates and fats is the nitrogen content, which is essential for making the countless proteins and other nitrogenous compounds the body needs. The body maintains nitrogen balance by adjusting both intake and excretion, and excess nitrogen is disposed of as urea. For reference, protein is about 16% nitrogen by weight, underscoring why nitrogen is the key contribution.