Protein is one of the three basic macro-nutrients comprising the foods we eat. (The remaining two are fat and carbohydrate.) On a molecular level, protein consists of long chains of nitrogen-containing subunits known as amino acids. Of the 21 different amino acids that go into building a protein chain, nine of them are considered essential amino acids because the human body lacks the physiological machinery to assemble them from their component parts. Of the remaining twelve amino acids, three of them are considered to be conditionally essential because, in many instances, our bodies become too overwhelmed to assemble them in sufficient quantities.
You do not have to know the names or recognize the different structures of the various amino acids to grasp the significance of adequate protein intake. However, it is important to appreciate that over half of all amino acids cannot be manufactured by the body in sufficient quantities to promote muscle toning, and that adequate amounts of these amino acids must be included in the diet.
Although proteins contain four calories per gram, they do not ordinarily serve as primary fuel sources. Instead, proteins are the main building blocks of virtually every living animal tissue. The structural integrity of the human body, from tendons and ligaments to muscles and organs, relies on a protein frame-work. To maintain, repair, or add to existing tissues, the body must synthesize genetically defined protein configurations. Although this principle applies to virtually all tissues, adequate protein intake is especially important for maintaining muscle mass.
Unlike your internal organs, which are surrounded and protected by your rib cage, pelvis, and skull, peripheral organs like skin and muscle are more vulnerable to environmental stressors. Our skin acts as a physical barrier between us and the outside world. It is our first line of defense against insect bites, burns, infectious agents, radiation, allergens, sharp objects, blunt force, friction, and countless other potentially damaging assaults.
Although our muscles must also contend with many of these same dangers, the greatest source of muscle trauma is actually muscle use. Physical exertion causes microscopic damage, known as micro-trauma, within muscle fibers. It takes a steady supply of raw materials to repair and maintain healthy skin and muscle.
So, if you want both vibrant, young-looking skin and a firm, toned physique, you must provide your body with ample amounts of high-quality protein. By “high quality,” I mean protein that contains a significant compliment of essential (and conditionally essential) amino acids. Protein foods that derive from animal sources, such as dairy products, eggs, poultry, meat, and fish, are rich in essential amino acids. These foods are also great sources of nitrogen, which is integral to the synthesis of many important compounds including nonessential amino acids.