Protein Supplementation in Athletes

As a Kinesiology major, I know many active people that are concerned with their health and are aware that the overall quality of health of an individual can be improved by engaging in physical activity and regular exercise. One of the popular topics of conversation and something that is seen on a regular basis in advertisements is the use of protein supplements, which are supposedly helpful in keeping an athlete active and strong throughout tough workout regimens. Personally, I was first exposed to the idea of an increased protein diet from my younger brother, who is a high school athlete that engages in a high amount of physical activity on a daily basis. At the young age of fifteen, he was already drinking whey protein after workouts, began to eat protein bars on a regular basis and was even told by his coaches that protein can help with athletic success. Specifically, this made me question how exactly a diet consisting of an abundant  amount of protein help an athlete. Is this practice really beneficial in exercise recovery or can a diet that is very high in protein lead to negative effects on an individuals health? I feel like all athletes and active people alike pose these questions to themselves; however, never seek out true answers. People fall into the trap of believing everything that advertisement companies say in order to sell their products. Athletic success is one of the most important concerns to an athlete at any age and many individuals will try anything that may aide in an increase in overall performance. 


Originally, being brought to my attention on a personal level, the idea of a diet high in protein was suddenly sparked once again when I came across an advertisement on the side of my Yahoo homepage. In bold print it read, “High-Protien Diets Can Have Surprising Results,” and included a photo displayed under the statement which put the viewer of the ad in a surprising situation (1). As I looked at the picture, it seemed like I, the viewer, was laying on an operating table with two surgeons huddled above me. Reading the blurb associated with the photo, I was surprised to learn that a high-protein and meat heavy diet can increase the risk of osteoporosis, kidney disorders and even colon cancer. Then the short paragraph went on to explain that the most healthy diet a person can have is one that is high in fiber, low in fat, rich in fruits and vegetables and free of animal products. Thinking about my younger brother, I began to investigate the topic. Wrote at the bottom of the short, less than informative paragraph, was a key to where this interesting information had come from, it stated that the blurb was “brought to you by the Physician’s Committee for Responsible Medicine.”  

After using google search to look up any information on the Physician’s Committee for Responsible Medicine, I came across anarticle on their website (2) titled, “Analysis of Health Problems Associated with High-Protein, High-Fat, Carbohydrate-Restricted Diets Reported via an Online Registry.” This article talked about a diet high in protein from an animal source especially without a sufficient intake of carbohydrates can cause many health issues. It was stressed that this practice can cause, for example, reduced kidney function, cardiovascular disease and an increased risk of cancer. Through this article I learned that an individual’s kidney function can be decreased because “high protein increases renal acid secretion and calcium resorption from bone which can reduce renal calcium resorption in the body. Also, animal protein is a major dietary source of purines, a precursor to uric acid.” When this uric acid builds up in the body, it competes with ketone bodies in the kidneys for renal tubular excretion, which can otherwise be explained as competition to simply leave the body. When this competition exists, uric acid can build up even more, causing reduced function and even kidney stones, which can be extremely painful. In addition to reduced kidney function, an individual can also experience an increased risk in cardiovascular disease due to the high fat content in foods with high animal protein as well as an increased risk of roughly 300 percent for colorectal cancer because “high protein diets are typically low in dietary fiber. Fiber facilitates the movement of wastes, including intralumenal carcinogens, out of the digestive tract and promotes a biochemical environment within the colon that appears to be protective against cancer.”

The article spoken about above was very informative in describing why a high level of animal protein in a person’s diet was detrimental to overall health; however, I wanted to discover more about specific protein supplements used by athletes in addition to a diet high in protein rich foods. This question brought me to an article written by a nutrition counselor, Nancy Clark, from SportsMedicine Associates in Brookline, Massachusetts (3). Featured on www.active.com, the entry titled, “Athletes and Protein: The Truth About Supplements,” did a wonderful job in explaining an athletes true need for protein. Clark describes that only 10-15% of  total calories need to come from protein. Of course, the more calories that are consumed, the more of a percentage of those calories will come from protein. We all know that athletes are hungry and require a greater caloric intake than sedentary individuals, which often stimulates the common misconception that athletes need more protein. However, Clark also made a point in explaining that an athlete can get the adequate amount of protein needed from a healthy diet. If this is statement is true, in addition to the fact that when the body’s fuel is scarce it can use protein for energy, then, it is common to think that the more protein that is consumed, the more energy the body can make for increased athletic performance. This common thought; however, is false because even though the body is able to use protein for energy in certain situations, it is not the primary source of energy in the body, carbohydrates are. When an athlete eats foods that are high in protein, it may limit the amount of important carbohydrates from the diet.  

The production of energy, overall, in a person’s body stems from the production of energy in each individual cell through a process called cellular respiration. This process consists of 3 steps, when oxygen is present, glycolysis, the TCA cycle and the electron transport chain and can be refereed to as aerobic respiration, primarily used by athletes that train using muscle-building resistance exercise. Cellular respiration can also happen in two steps, glycolysis and fermentation, when oxygen is not present for the body to utilize, which takes place when an athlete is taking part in a long duration of vigorous intensity exercise. In this situation, much of the oxygen is depleted and is used quickly rendering the body unable to primarily use the oxygen it has left in the blood and tissues for energy production.

When oxygen is available in cellular respiration, aerobic respiration, the cell uses glucose, which is a 6 carbon sugar molecule, retrieved directly from the carbohydrates a person consumes, to start to make energy. This energy can be referred to as ATP, or adenosine triphosphate. The glucose molecule is first fed into the initial step of cellular respiration, glycolysis, and is changed multiple times into different molecules with the help of enzymes and other factors, ending with the production of 2 molecules of ATP, two molecules of NADH and 2 molecules of Pyruvate, a three carbon molecule. The 2 molecules of NADH are mainly saved to use in the third step of aerobic respiration and pyruvate is used in the next step, the TCA Cycle. A single molecule of Pyruvate, one at a time, is converted into Acetyl-CoA in order to enter this cycle. After the cycle is complete, the cell will have produced two molecules of ATP, which is added to the 2 molecules already produced in glycolysis, totaling 4 molecules of ATP thus far. The TCA cycle also yields 8 molecules of NADH, 2 molecules of FADH which are used in the following, final step of aerobic cellular respiration along with the 2 molecules of NADH from glycolysis. The electron transport chain is the final step and uses the ten total molecules of NADH and the two total molecules of FADH to create a proton gradient and give the electrons from each molecule to a sequence of electron carrier complexes. Each complex is at a lower energy level and as the electrons are passed, energy is released and used to to pump the protons, from the gradient that was created, across a membrane, to the final electron acceptor, oxygen and specifically resulting in 28 molecules of ATP and water, a bi-product.  This whole process of aerobic cellular respiration ultimately makes a total of 36 molecules of adenosine triphosphate, or ATP. When the body does not have oxygen; however, it is not possible to go through the TCA cycle or the electron transport chain. The molecule of glucose is pumped through glycolysis, yielding 2 molecules ATP, 2 molecules of pyruvate and 2 molecules of NADH. The 2 molecules of ATP can be used for energy; however, the pyruvate is exposed to the enzyme lactate dehydrogenase and forms lactic acid, which builds up in the muscles. As you can see in the photo above summarizing metabolism, in the electron transport chain, the ATP produced can then also be recycled, turning into ADP (adenosine diphosphate, seen in the Marvin Sketch window at the bottom of this blog). The breaking off of the third phosphate group of the ATP is what gives a majority of cells energy to do work. What many people may not know, even those familiar with anaerobic cellular respiration, which I discovered (4) is that the lactic acid that builds up in muscle diffuses into the blood and can be utilized for energy or can be taken to the liver and used to create stores of glycogen which can, in turn, be tapped into for molecules of glucose in order to start up another cycle of energy production, or cellular respiration. 

The Body's Energy: ATP

 I began to wonder, since carbohydrates are the primary fuel for the body, then are proteins and fats ever used to generate energy, also known as ATP? I found that only when carbohydrates are not available for the body to use will the body utilize protein and fats to fuel the process of cellular respiration. In order to use proteins it is necessary for them to be broken down into their respectful amino acid counterparts, the amino group is knocked off and the remaining carboxyl group, -R side chain and alpha carbon linkage is then used to create a molecule of  pyruvate (figure). Due to this production of a pyruvate molecule, it is known that the glycolysis can be skipped and the pyruvate can either enter into the TCA cycle if oxygen is available or into the process of fermentation is oxygen is not present. In the case of pyruvate entering into the TCA cycle and skipping glycolysis, the net yield of ATP will be less than that of carbohydrates. When fats are utilized, on the other hand, they are broken down into their counter parts, fatty acids and glycerol. The glycerol is converted into a molecule of G3P, also known as glyceraldehyde-3-phosphate, a molecule in glycolysis, and the fatty acids, where most of the energy from fats are stored, are broken down into “two-carbon fragments by a metabolic sequence called beta oxidation. These two-carbon chunks are then added into the citric acid cycle as acetyl Coenzyme A (or acetyl CoA). Interestingly enough, NADH and FADH2are also generated during beta oxidation and are useable by the electron transport chain to make even more ATP (5).” 

It is seen through the information gathered that even though carbohydrates are used primarily for energy production, proteins and fats can be used in cellular respiration as well under the circumstances that the level of carbohydrates in the body are low. Proteins will yield slightly less energy than carbohydrates when looking at a single gram but averaging at around the same amount of energy, and when fats are used, one gram of fat will yield more than twice the amount of energy than one gram of carbohydrate. So in no way is it more beneficial for an athlete to use mostly proteins, at just under 4 kcals/g of energy, instead of the commonly used, primary source of energy, carbohydrates, at around the same 4kcals/g of energy; however, there is a benefit to utilizing fat stores due to the high, 9 kcals/gram, of energy produced from the oxidation of lipids. 

 Knowing now that protein only makes up some of the energy produced by the body when carbohydrates are not available, I found an interesting study that showed that even an increase in protein intake, far above the amount you ingest during a mixed nutrient filled meal, will not stimulate muscle protein synthesis any more than when you provide your body with the essential amino acids needed through healthy eating alone. In a study done by scientists, Bohe, Low, Wolfe and Rennie, at the University of Texas and the University of Dundee in the UK (6), it was proved that the amount of amino acids that are ingested does effect your muscle protein synthesis; however, too high of a level of amino acids can cause synthesis to plato. When the level of essential amino acids in the blood are raised from basal/fasting levels by 50-80%, synthesis of muscle protein shows a linear increase, but once above that level, the synthesis is saturated. This seems to prove that even though essential amino acids are necessary for synthesis, the level at which synthesis is active is within a narrow range. Too much protein intake can therefore cause a reduction of muscle protein synthesis because of the saturation that is activated when the concentration of amino acids available to use is too high. 

When seeing that carbohydrates are truly responsible for the primary production of energy, I went back to my younger brother with this newly found information and I was faced with one last question about a common idea which athletes believe to be true about the intake of additional protein. After exercise, will ingesting a protein enriched supplement, such as a shake or snack bar, increase the speed of glycogen synthesis resulting in faster recovery? According to a study done by scientists, Hall, Shirreffs and Calbet, that was published in the Journal of Applied Physiology, there is no additional benefit when consuming a combination of carbohydrates and proteins when compared to consuming carbohydrates alone after exercise (7). The additional amount of protein that was ingested, that was once thought, when paired with carbohydrates, would increase the rate of glycogen synthesis actually does not have significant differences from ingesting carbohydrates alone. The coingestion of protein and carbohydrates after exercise as well as the ingestion of carbohydrates alone both did however, result in a greater synthesis of glycogen when compared to a placebo, water model. This tells us that carbohydrates alone, can be just as beneficial to our bodies in recovery as a protein-carbohydrate supplement. The extra carbohydrates needed after a bout of exercise that can increase glycogen synthesis can be obtained by eating a healthy snack, rich in complex carbohydrates such as fruits, vegetables, whole grains and legumes (8). Therefore, from all the information complied in this blog, I now believe it is possible to finally conclude that additional protein intake after exercise and a diet high in protein, especially when paired with an inadequate amount of carbohydrates, can overall be more harmful to your heath than helpful when trying to increase performance and athletic success.

Resources: 

1. Safe Diets

http://www.atkinsdietalert.org/images/print-ad-large.gif

2. Physicians Committee for Responsible Medicine 

http://www.pcrm.org/health/reports/analysis-of-health-problems-associated-with-high

3. The Truth about Supplements

http://www.active.com/nutrition/Articles/Athletes_and_protein__The_truth_about_supplements.htm

4. Lactic Acid Facts 

http://sportsmedicine.about.com/cs/exercisephysiology/a/aa053101a.htm

5. Cellular Respiration, Breakdown of Carbohydrates and Fats

http://wiki.answers.com/Q/How_are_fats_and_proteins_broken_down_in_cellular_respiration

6. The Journal of Nutrition: Human Muscle Protein Synthesis
http://jn.nutrition.org/content/132/10/3225S

7. Journal of Applied Physiology: Muscle Glycogen Resynthesis  

http://jap.physiology.org/content/88/5/1631.short

8.  Livestrong: Complex Carbohydrates

http://www.livestrong.com/article/27398-list-complex-carbohydrates-foods/