Proteins Are Often Called theTerm Paper

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[. . .] 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.

First, numerous studies have been conducted in an attempt to discern what an athlete who participates in resistance training can maximally turn into muscle. These studies seem to indicate that the most protein any athlete can readily convert into muscle mass is approximately 1.7 to 1.8 grams of protein per kilogram of body mass per day (Berning 54). Anything beyond this rate is excessive, even for athletes, and will simply be used as energy or stored as fat. So, aiming to maximize protein intake would be a mistake for strength training -- instead this rate should be aimed for.

Second, although this rate is significantly greater than the RDA, it is "more than likely it is less than most persons currently consume." (Berning 50). This fact may be surprising; but for some strength-training athletes to reach their optimal protein intake, they may have to decrease the amount of protein they eat.

Similarly, athletes participating in resistance exercise routines with an emphasis on endurance should also aim for the 1.7 to 1.8 gram rate of consumption. The only significant difference being that they may require higher levels of Creatine to restore the adenosine triphosphate that is lost during these types of workouts (Berning 52).

The other category of athletes that may benefit from additional levels of protein are aerobic endurance athletes. As evidenced from the physical stature of these athletes, aerobic training does not significantly add to muscle mass, but as mentioned before, there are significant increases in amino acid oxidation that need to be accounted for. "Increased amino acid oxidation has been shown to occur during prolonged exercise and could contribute 5% to 10% of the energy needs." (Berning 53). Therefore, experts suggest that aerobic endurance athletes consume 1.2 to 1.4 grams of protein per kilogram of body mass each day (Berning 53). Yet again, this amount is probably less than most Americans already consume. So, although these types of athletes require more protein than sedentary individuals, they may find that they need to reduce the level of protein they eat to reach their optimum level.

Many of the adverse affects of ingesting too much protein are linked to the types of foods that contain a lot of protein -- namely red meats. Body builders in particular are notorious for consuming mass quantities of red meat. During recent years, in light of the research done on saturated fats, many of these athletes have switched to protein supplements to avoid such drawbacks. Yet many researchers believe that protein supplementation, for most athletes, is overkill. "Much marketing of whole protein and amino acid supplements is directed to both endurance and strength athletes. Yet clearly, an athlete's elevated protein needs are easily met or exceeded on an adequate calorie diet, rendering protein supplements unnecessary." (Ryan 73). Protein supplements have been shown to neither be digested more readily, nor have they been shown to significantly reduce the amount of calories that would be consumed on a lean protein diet. Too much protein, from food or otherwise, will be converted into fat and can lead to health problems. Essentially, even the increased protein requirements of athletes should not warrant mass intakes of any products that can supply these needs.

Works Cited

1. Berning, Jacqueline R. And Suzanne Nelson Steen. Nutrition for Sport and Exercise. Gaithersburg: Aspen Publications, 1998.


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