Proteins from your diet fulfill diverse and dynamic roles in the body. Along with carbohydrates and fat, protein from food is one of the three vital energy nutrients needed by the body. More than just an energy source, protein is a life-sustaining nutrient involved in many key bodily functions as well as a supplier of several B vitamins, iron, zinc, magnesium and most notably, amino acids.
Long strands of amino acids assemble, twist and turn to form proteins. You break down dietary protein into individual amino acids, which your cells then reassembles into various types of proteins used for many functions. Proteins assembled from amino acids are found in every cell in the body and serve many roles from structural support and cell messengers to the creation of enzymes. Some amino acids can be made in the body, but the remaining essential amino acids must come from protein sources in the diet.
Source of Energy
Protein, carbohydrates and fats supply the body with all of its energy needs. Though protein is not the body’s preferred energy source -- your body prefers to run on carbohydrates or fats -- it's vital to ensure the body receives essential amino acids. The Dietary Guidelines for Americans recommend that 10 to 35 percent of total calories come from protein foods. Animal-based proteins such as meat, fish, poultry and dairy are complete proteins, supplying all of the essential amino acids. Plant-based proteins including beans, grains, nuts and vegetables are incomplete, containing some, but not all of the essential amino acids.
Growth and Repair
Protein’s primary role is in muscle growth and repair. As the structural basis of muscle fibers, cells and tissues, proteins provide the amino acids needed to repair damage to muscle fibers, replace tissues and promote growth. Proteins are not only the major components of muscle tissue, they also assist in muscle contraction and body movement.
The body uses protein to support a healthy immune system. When confronted with a harmful substance, called an antigen, your body uses amino acids to produce antibodies. These proteins that protect you from pathogens by binding with antigens, which help remove the pathogens. This response to antigens is often exaggerated in individuals with allergies. When an allergy exists, the body treats an otherwise harmless substance as an antigen, which triggers allergy symptoms.