Protein is a nutrient that is critical to keep your body functioning normally. When you consume protein-containing food, your gastrointestinal tract digests it, breaking it down into its building blocks, amino acids. These molecules are absorbed into your blood and travel to all of your cells, which use them to construct many different new proteins. Examples include enzymes that fuel biochemical reactions, structural proteins in your muscles and proteins that control what molecules can enter your cells. Meat is a complete protein source that provides all the essential amino acids, according to the Centers for Disease Control and Prevention, which also says you should consume about 50 grams of protein daily. In general, a 3-ounce piece of red meat -- the serving size recommended by the Mayo Clinic -- contains about 21 grams of protein, and poultry has about 15 grams.