Do Proteins Help the Body as Related to Sports Exercise and Nutrition?

Proteins are often called the building blocks of life. In fact, the very word "protein" implies their importance in the body: it is a Greek word meaning "first place." Approximately fifty percent of the dry weight in animal cells is comprised of protein (Campbell 71). They play a roll in almost everything the body does and "are used for support, storage, transport of other substances, signaling from one part of the organism to another, movement, and defense against foreign substances." (Campbell 71). Proteins are essential to the proper functioning of every organism known to man.

The human genetic code holds the instructions for the making of over ten thousand different types of proteins; all with specific purposes. Additionally, "Proteins are the most structurally sophisticated molecules known." (Campbell 71). In comparison to other molecules, proteins are enormous and come in nearly every shape imaginable. However, despite their variety and size, proteins are simply polymers made up of only twenty different amino acids. What makes one protein different from another has to do with the ordering of these amino acids and the shapes that they form. "By varying the numbers of different amino acids and their sequences, the body creates proteins of skin, blood, muscle, hair, bone, and nails, as well as enzymes, the catalysts that speed up chemical reactions of cells." (Ronzio 539).

About sixteen percent of protein is nitrogen (Ronzio 539). Accordingly, a rough estimate of protein content in food can be calculated by measuring the amount of nitrogen in that food. What the body generally gets out of this food is not a full protein itself -- that is broken down during digestion -- but the amino acid ingredients to build a protein. "Digesting dietary proteins supplies essential amino acids that cannot be made in adequate amounts by the body." (Ronzio 540). The body's DNA holds the information necessary to build any given protein, and the dietary amino acids are grabbed by biological processes to make-up the protein that is being coded for.

If an individual ingests a surplus of amino acids -- more than the body requires -- they are not converted directly into proteins, but instead, can be burned off as energy or stored as fat. So, it would seem from a biological standpoint that the amount of protein, in the form of food, that is taken in by the body should be proportional to the amino acid requirements for that person. However, "Most Americans eat more than enough protein to meet their amino acid needs." (Ronzio 540).

In accordance with the observation that proteins are large and complex molecules it should not be surprising that breaking them down to their amino acid components, via digestion, is a costly endeavor in terms of energy. "Protein digestion normally begins in the stomach where the strong acid (hydrochloric acid) unfolds protein in food, rendering it more accessible to attack by the digestive enzymes of the stomach. The initial phase of protein digestion yields fragments called peptides, rather than individual amino acids." (Ronzio 540). Further on in the digestive process, the pancreas and then the intestines continue to assault the peptides until, finally, individual amino acids are freed and released into the bloodstream.

Each of the aforementioned chemical processes require energy, which ultimately detracts from the net amount of energy acquired from the food. This is probably why, through their evolutionary history, humans have developed a taste for cooked forms of protein. "Cooking foods denatures and partially breaks down proteins, making them more accessible to digestive proteins." (Ronzio 540). By cooking our foods, we have increased the net amount of energy that can be freed from them.

Over the course of any given day the proteins that are in place and allow our bodies to function eventually get worn out and degrade. This is the underlying premise for the necessity of including protein in a diet: these degraded proteins need to be rebuilt and replaced. "A steady input of essential amino acids is therefore required even when the body is at a stable weight. The recommended dietary allowance (RDA) of .75 g protein per kilogram of body weight for adults was based upon long-term and short-term studies of humans." (Ronzio 541). So, for example, a 174 pound male requires a protein intake of 63 grams daily. Obviously, this rate is different for children because they require more protein to support their rapid growth. This RDA has been established as what the average adult should ingest each day.

Yet, when individuals attempt to maximize their physical capabilities, may times they try to alter the diets recommended for average adults because they consider themselves atypical. "Historically, many athletes believed that consuming large quantities of protein was the key to successful athletic performance." (Berning 45). Much research performed in the nineteenth century indicated that protein was the primary fuel for strenuous exercise. However, subsequent research revealed that carbohydrates and fats were far more efficient sources of energy.

'Beginning in the 1970's, research investigations began to show that athletes might require a greater protein intake than their sedentary counterparts. More recently, information has become available that the protein requirements of athletes may depend upon the type of physical activity they do and that athletes participating in different activities need this enhanced protein intake for varying reasons." (Berning 46). In other words, a world class weight lifter's protein requirements will be different from the requirements of a world class marathon runner, and both will be different from the requirements of a world class sprinter. Considering the facts that too little protein consumption can lead to protein malnutrition and protein over consumption can lead to other serious health problems, it has become essential in the world of sports to balance these two forces with specific consideration given to the activity an athlete performs.

The first risk is protein malnutrition. This, obviously, is protein deficiency taken to its extreme. "With inadequate dietary protein, yet with adequate calories, less muscle wasting occurs than with malnutrition due to a lack of both protein and energy sources because protein is not broken down so extensively." (Ronzio 542). With a dearth of amino acids on hand it becomes necessary for the body to borrow them from other places. In order for the body to maintain normal blood sugar levels and increase amino acid levels in the blood, muscle proteins must be used. As a result, the muscles of the body atrophy, and begin to fall apart.

Other health risks involved with protein malnutrition include: atrophy of the intestinal lining, reduced liver function, improper fluid balance, edema, anemia, and reduced levels of antibodies (Ronzio 542). Clearly, appropriate amounts of protein must be ingested to ensure proper functioning of the body. But, consuming too much protein can result in other serious health problems.

Although red meat is an abundant source of protein, it is also linked to high levels of saturated fat. So, individuals who try to maximize their protein intakes by eating lots of red meat are putting themselves at risk for health problems associated with high doses of saturated fat; "excessive saturated fat is linked to cardiovascular disease and to problems of overweight." (Ronzio 542). Furthermore, "The surplus waste products from burning excess protein place an extra burden on the kidneys." (Ronzio 542). Additional research has found possible links between protein over consumption and osteoporosis, liver cancer, blood cholesterol, and even stroke. So, eating an appropriate amount of protein is important to everyone because ingesting too much or too little can both have adverse affects on the rest of the body.

Somewhere between these two extremes is where today's athletes attempt to find protein levels that will boost their performance. Naturally, not all athletes understand the importance of a varied diet; and some even put their health at risk because they have inaccurate notions of how to maximize their results. Basketball great Charlie Ward remembers, "Back when I was playing college ball, I figured the best way to pack on muscle was to eat a lot of fat. My idea of the food pyramid was to stack a cheeseburger on top of a double cheeseburger." (Schlosberg xxvii). Assuredly, Ward was ingesting a lot of protein with this diet but he was also taking in exorbitant amounts of fat, saturated fat, and cholesterol.

Considering the long established RDA of protein, nutritionists have identified several categories of athletes that may require greater levels of protein to reach peak performance. These types of athletes include; "endurance athletes, athletes performing intense strength training programs, teenage athletes with growth as well as exercise requirements, exercisers and athletes following a calorie-restricted weight loss program." (Ryan 70).

The first group, endurance athletes, may need more protein because they incur increased protein fuel costs during training. The requirement comes about because exercise of a long duration can deplete glycogen stores in the body, and protein can be converted into glucose to accommodate immediate energy requirements. Additional protein is needed to repair tissues damaged by the extended duration of physical exertion.

Repair and recovery is also an important use of protein for strength-training athletes. "Though strength-training athletes often consume large amounts of protein in hopes of building more muscle mass, the actual requirements for this tissue building are relatively small. Protein consumed in excess of actual requirements will not be used to build more muscle, but rather will be converted and used as energy or stored as fat." (Ryan 71-72). So, for adult athletes the RDA can vary between 1 to 2 grams per kilogram of body mass per day.

To better analyze what appropriate levels of protein consumption are for athletes, rather than sedentary individuals, it is important to identify specifically what factors most strongly influence these protein requirements. "Because nitrogen balance may be affected by the intensity and duration of exercise, energy content of the diet, and the training level of the subject, care should be taken to control these variables when designing an experimental protocol. Gender has also been shown to affect the substrate used for energy production during exercise, and thus nutrient requirements may be different for male and female athletes." (Berning 47).

Exercise intensity has been shown to alter the rates by which amino acids are oxidized -- or converted to energy -- by the body. This has not been found to be a linear progression of intensity to oxidation, but rather an exponential relationship (Berning 47). Therefore, an exercise routine that is just slightly more intense than another routine may trigger the oxidation of a significantly larger amount of amino acid. This fact needs to be accounted for when considering the protein needs of an athlete with a particularly intense type of workout.

A second factor influencing protein requirements is the length of an athlete's workout. The observation that has lead nutritionists to this conclusion is, "An increase in blood urea concentration during intense, prolonged exercise has been shown after 60 to 70 minutes of activity. The increase in blood urea is presumed to be the result of an increase in amino acid oxidation, rather than a decreased removal rate caused by reduced kidney function during exercise." (Berning 47). Athletes who exercise for prolonged periods of time also will begin to employ amino acids as an alternate form of energy, and thus, require more in their diets.

A third factor to be considered in the protein requirements of an athlete is the amount of energy they typically consume. The general relationship between energy and protein intake has been found to be: the more energy an individual consumes, the less protein they will need to consume. "As stated previously, amino acids can be used to supply glucose; therefore, increased availability of glucose through carbohydrates necessarily reduces the oxidation of amino acids to glucose." (Berning 49). So, if an athlete eats a lot of fats and carbohydrates, their body will need less protein.

Unfortunately, nutritionists have yet to find any clear relationships between the training state of an athlete and the oxidation rates of amino acid in their bodies. "Henderson et al. found that the oxidation of continuously infused leucine was significantly greater in trained than in untrained rats both at rest and during exercise, and although the relative role of the amino acids as an energy source decreased with exercise, the absolute rate of leucine oxidation increased." (Berning 49). In other words, one particular type of amino acid was oxidized more readily in conditioned rats than in sedentary rats; but on the whole, the sedentary rats used more amino acids as a form of energy. The task, therefore, would be for conditioned athletes to increase their intake of that particular type amino acid relative to the others.

Research has also indicated that gender plays a role in the protein requirements of an individual. During a study of physically conditioned males and females, "The males excreted significantly more urea nitrogen during the exercise than the rest." (Berning 49). This indicates that the male athletes were making use of more amino acids than the females, and accordingly, would require more protein in their diets to re-supply their stock.

Exercise intensity, exercise duration, energy consumption, level of conditioning, and gender are the most significant variables concerning the protein requirements of any adult athlete. It should, therefore, be expected that athletes who partake in significant levels of strength training should have different protein needs than athletes who partake in significant levels of endurance training.

In general, most athletes feel that maximizing protein intake is the best path to improved performance. Yet, "These elevated protein requirements should be put into perspective. Basically, your increased protein requirements are easily met in a balanced training diet which is adequate in calories." (Ryan 72). This is because, contrary to many athletes' beliefs, the additional protein they require is mostly being used to supply their bodies with energy -- not to build muscle or to increase strength. Of course, some protein is being used for this purpose, but by greatly increasing protein intake they are mainly just increasing their energy supply.

Understanding this point, it is now possible to determine what the best diet should be for different types of athletes. Regular resistance training should, usually, result in an increase in muscle mass and muscle strength. "However, for muscle to be enhanced, the athlete must be in a state of progressive nitrogen balance. Thus, to maximize protein synthesis, sufficient amounts of amino acids must be made available to the muscle." (Berning 50). On the surface, it would seem that if an athlete wants to increase their muscle mass they should simply increase the amount of protein they consume. But, there are two reasons why this might not be the case.