Proteins are one of the most important building blocks for good cell formation and energy production. Proteins are a class of nitrogen-containing compounds that are comprised of amino acids. Proteins are essential for anabolic growth and repair processes throughout the body. All tissues in the body are made of protein – muscle cells, skin cells, collagen, keratin (hair and nails), and red and white blood cells. Enzymes in the body are composed of protein, as are hormones and antibodies. Certain amino acids are needed for production of the different neurotransmitters in the brain. Lean protein is considered an excellent source of fuel for energy. Many experts recommend that a high-nutrition diet consist of approximately 25% protein.