Proteins are composed of individual amino acids and are a fundamental aspect of the human body. Amino acids are very similar in composition but their slight variance (the “R-group,” “functional group,” or “side chain”) is what decides their function. There are two types of amino acids; the first is “essential” which means that the body does not make it itself (or make enough itself) so it has to come from the diet. The second is “nonessential”, which is the kind the body can produce. Out of 20 amino acids total, 9 are essential and 11 are nonessential.
Proteins have numerous functions in the body. The most common job of protein is serving as building blocks for muscles, blood, skin and even replacing dead cells. They also form enzymes, which are materials that help break down or build substances and facilitate reactions. Some hormones are proteins, including testosterone and estrogen. Proteins also assist with fluid regulation and balance. For example, if the protein concentration is too high on one side of the cell membrane it will attract water and other fluids, this causes swelling and is most often seen after an injury. Another function of proteins is transporting substances across the cell membrane. A protein has a negatively charged nature it attracts positively charged hydrogen atoms, and because of its relationship with hydrogen atoms it acts as an acid-base regulator. In extreme cases (ex: starvation), proteins can be broken down and used as energy, although it should be noted that this is not their intended purpose. These are just a few examples of their usefulness but proteins are capable of much more!
Now that we understand how important proteins are let’s take a look at how to eat enough of them. When it comes to foods there are high-quality proteins and low-quality proteins. A high-quality protein contains all of the essential amino acids and easily digestable and a low-quality protein does not. It’s important to understand that although some foods do not supply all of the essential amino acids they are still useful to the body. In fact, low-quality proteins may be eaten in combination with each other to supply all of the essential amino acids; this makes low-quality proteins a complete meal for amino acids. For example, eating legumes may provide only partial of what the body needs, so if you pair them with grains you will get the other half of essential amino acids. Those who prefer to avoid eating meat, poultry, fish, cheese, eggs, milk, and some soybean products will typically utilize “protein complementing”. Protein complementing is the act of combining low-quality proteins to form a meal composed of all of the essential amino acids.
Proteins are necessary for everyone, not just bodybuilders; however, it’s easy to eat the wrong amounts. The DRI (daily recommended intake) recommends ingesting 0.8 grams for each kilogram (2.2 pounds) of body weight to maintain muscle mass. So, for example, a 150 lb individual should be eating 54.5 grams of protein daily (150lb / 2.2lb = 68g, 68g x 0.8g = 54.5g). An example of 54.4 grams is one blade steak or two 4oz. chicken breasts.
Sizer, F., & Whitney, E. (2012). The Proteins and Amino Acids. In Nutrition: Concepts and Controversies (12th ed., pp. 189). Belmont, California: Yolanda Cossio.
Whitney, E., & Rolfes, S. (2013). Protein: Amino Acids. In Understanding Nutrition (13th ed., p. 166). Belmont, California: Yolanda Cossio.