You cannot survive without protein. This vital nutrient should make up about 10 percent to 35 percent of your daily caloric intake, according to the University of Illinois McKinley Health Center. Each gram of protein contains about four calories, so based on a 2,000-calorie diet plan, you would aim to take in 200 to 700 calories from protein each day. Protein supports many bodily systems, including cell growth, immune function, metabolism and hormone production.
The main function of protein in the body is to build and repair cells and tissues. This includes supporting muscle development and all other cells in the body. Certain amino acids – the building blocks of protein – are particularly beneficial for muscle repair and growth. These amino acids are called the branched-chain amino acids, or BCAAs. According to a 2004 report from the department of health and exercise science at The College of New Jersey, published in the “Journal of Sports Science and Medicine,” BCAAs help prevent muscle breakdown during exercise. The three BCAAs include leucine, valine and isoleucine.
Protein plays a role in virtually every aspect of your immune system. According to the University of California Los Angeles, UCLA, people who consume too little protein have low immunity and are at risk of getting sick more frequently. White blood cells, made from proteins, attack viruses and bacteria in your bloodstream. Certain sources of protein, such as dairy or whey, help boost levels of glutathione in your system, which is an antioxidant that helps fight bacteria and viruses.
Hormones are composed of proteins. Protein and amino acids also support hormonal secretion. Protein plays a vital role in the release of two of the most important hormones for muscle development, including testosterone and human growth hormone, HGH. According to Richard B. Kreider, Ph.D. of the Exercise and Sport Nutrition Laboratory at the University of Memphis, there’s evidence that certain amino acids promote the release of muscle-developing hormones like HGH. Arginine was shown to promote the release of HGH. Foods rich in arginine include soy, spinach, turkey and seeds.
Your body can convert individual amino acids to energy when needed. Although protein is not the body’s main source of energy – glycogen from carbohydrates is the preferred source – excess protein/amino acids may metabolize to form glycogen when your body’s stores are low. Another healthful benefit of protein is in liver health. According to the previously mentioned study in the “Journal of Sports Science and Medicine,” protein helps repair damaged liver cells in patients with liver disease or those suffering from alcoholism.
- University of Illinois McKinley Health Center: Macronutrients: the Importance of Carbohydrate, Protein, and Fat
- “Journal of Sports Science and Medicine”; Protein – Which is Best?; Jay R. Hoffman, Michael J. Falvo; September 2004
- University of California, Los Angeles: Protein
- SportSci.org; Effects of Protein and Amino Acid Supplementation on Athletic Performance; Richard B. Kreider; 1999