Protein and amino acid supplements receive a lot of attention on health-food store shelves, and there's a good reason.
Protein, as the second-most-plentiful substance in the body (after water), is needed for the growth and repair of every cell in the body. Muscles, not surprisingly, are primarily made up of protein.
Skin, hair, nails, antibodies, many hormones, and enzymes are also mostly comprised of, you guessed it, protein.
Protein profile