Protein plays an essential role in the body's ability to build and repair muscle tissue. Approximately 17% of the human body is made up of protein. You need it for your muscles, your skin, your internal organs, and in particular, your heart and brain, as well as your eyes, hair, and nails. It is also required by our immune system to make antibodies necessary to combat infection. Additionally, proteins are involved in regulating blood sugar, metabolizing fat, and producing energy. As you can tell protein plays very vital roles in keeping your body healthy and energized.