View Full Version : Nutr., Supplements & Kidney Disease (Research Paper Critique)

04-27-2010, 03:40 PM
Thought I'd see if I could get some input, sources, advice, etc... on a recent research paper wrote. There is still alot of info on the topic I'd like to cover, so constructive criticism is appreciated. Hopefully, this will be informative to some people.

Optimal Nutrition or Suppplementation: How The Kidneys Affect Performance

The ongoing search for the “magic pill” has led many athletes and others to stray from a good nutritional foundation. Unbeknownst to these weary searchers of the proverbial “holy grail” of supplements, their pursuit steered them in the wrong direction when the answer they have been looking for was under their noses the whole time. They have fallen for false claims and promises that what they “need” to improve their performance or health can be found in a few scoops of powder or a handful of pills.

Eating a nutrient-dense diet full of the vitamins and minerals that have an astounding effect on health and performance is considered too difficult or too easy to be effective and, consequently, completely dismissed. The decision to choose supplementation over a nutrient-dense diet has life-changing consequences for them, many of which are silent and undetectable until it is too late. One of the most overlooked areas of the body that is impacted the most by these decisions is the kidneys. Some of the most common supplements (creatine and protein) believed to enhance athletic performance, are in fact the most potentially damaging to the kidneys.

Some of the responsibilities of the kidneys are removing waste and drugs from the body, producing hormones that regulate blood pressure, balancing the fluids of the body, producing a form of vitamin D for bone health and controlling the production of red bloods cells, amongst many other functions. By not supplying the body with a nutrient-dense diet and resorting to supplementation, a two-fold effect occurs. The kidneys are deprived of the nutrients they need for optimal performance, while increasing the stress and workload required of them. Kidney damage or nephritic syndrome may occur as a result of having to filter the excess amounts of toxins from the supplements. As kidney function declines, waste levels in the blood can build up as well as other problems, such as high-blood pressure, anemia, weak bones, nerve damage, and an increased risk of heart and blood vessel disease. Athletic performance will decline as kidney function declines. From a comparative study of health and performance when dealing with an athlete’s choice of diet, it is apparent that a nutrient-dense diet is superior to supplementation for athletes, especially when comparing the relationship between supplementation and chronic kidney disease (CKD) and the effects each has on performance and health.

Supplements can be very effective for improving an individual’s health or performance, when they are used responsibly. Dietary supplements are of particular concern because of the potential for mislabeling and contamination with banned substances, especially when their ads are notorious for making bold and unsubstantiated claims.1,2 Iron requirements for athletes are much greater than that of the average person, especially for endurance athletes whose iron requirements are increased about 70%.2 (pg 8) Iron deficiencies can hinder an athlete’s performance by impairing muscle function and limiting work capacity. Given the direct effects an iron deficiency can have on performance, it is surprising to find it is one of the most common deficiencies found in athletes.

Although there are a number of supplements, safe and otherwise, the two most well known to athletes are protein and creatine. Along with being the most well-known, these two are also the most misunderstood supplements. The recommended daily allowance (RDA) for protein for the average person is about 0.8 g/kg.2 (pg 8), 3 Current, and still debated, research suggests athletes may need anywhere from 1.2 to 2.0 g/kg of protein.3 (pg 134) It is important to note that most people already consume 1.5 to 2 times the 0.8 g/kg RDA of protein without the use of supplements.4 Although not as widely accepted beliefs as they once were, there are still a number of people who are misinformed that protein is the primary fuel source for muscles and that increased protein consumption directly improves performance. A tolerable upper intake level (TUL) for protein has yet to be established due to the lack of studies conducted in regards to the long-term effects of high protein diets, 4 (pg 888) when the amounts consumed begin to exceed 2.0 g/kg. When looking at the available epidemiological evidence and short-term studies concerning excess protein consumption above what an individual’s body is able to utilize, the same approach that is taken to sift out some of the inaccurate perceptions, encouraging the use of excessive amounts of protein, should also be applied to the believed health risks lacking sufficient data.

While there are a number of concerns about the safety of consuming significant amounts of extra protein, the kidneys are impacted the most. When protein is broken down and metabolized by the body, the kidneys filter and excrete urea that has emerged as a waste product of protein metabolism.3 (pg 143) Consuming excessive amounts of protein increases the amount of stress placed on the kidneys to remove urea. Short-term studies do not appear to show any adverse affects of this increased stress for athletes with normal kidney function.3 (pg 143) Although long term studies are lacking on the effects of continued stress placed on the kidneys, it would seem only prudent to assume continued stress on the kidneys will result in negative consequences. One indirect concern is the increased risk of dehydration that results from a combination of both the amount of water needed for the digestion of proteins, as well as the amount of water lost in urine that results from increased excretion of urea.3 (143) The importance of adequate protein consumption is undeniable; however, the benefits of consumption, to the extent they have been taken, are less than accurate. While there is still a need for more extensive and long-term studies in regards to possible risks associated with high protein consumption,4 (pg 887) the available research strongly supports a correlation between protein intake and kidney function. It is imperative that athletes understand their own personal needs when increasing their protein intake and err on the side of caution if amounts become excessive of 2.0 g/kg.

04-27-2010, 03:41 PM
Creatine supplements are widely used by many athletes for various reasons. The most noticeable benefit is an increase in performance for short-term high intensity exercise.2 (pg 11) Creatine supplementation generally entails consuming 20 grams daily for the first 4-6 days, then 5 grams daily for the next 2-3 weeks.5 Like protein, the byproduct of creatine breakdown, createnine, is excreted in the urine. Excess creatine intake, above what the body can utilize, does not provide any benefits and is excreted in the urine.5 (pg 2891s) Interestingly enough, many athletes take creatine supplements because of the rapid increase in body mass that occurs from water retention. Many associate the increase in muscle mass with an increase in strength, but studies have found no difference in the strength between athletes taking creatine and those taking a placebo.5 (pg 2891s) There are no long-term studies over the safety of prolonged creatine use; however, given the probability of excessive doses and the increased work of the kidneys, it comes as no surprise that there are a growing number of reports concerning renal damage and other issues relating to creatine supplementation.

Somewhere along the road, society has been led to believe that improvements in their health and performance are just a bottle of pills away. Ironically, when the product in which they had once placed their faith does not meet their expectations, they then continue to repeat the process, in hopes that a different product will be the key to their success. Rarely do these people realize how much more complicated they are making everything. The majority of people attained some sort of basic knowledge throughout their life about eating a variety of fruits, vegetables, grains, and meats, while limiting their intake of “junk” food. Something so basic and simple has been labeled as too difficult or too time consuming to follow. Ease and convenience have replaced healthy practices of consuming nutrient-dense foods with that of consuming energy-dense foods. RDAs for vitamins and minerals essential for optimal health and performance are rarely met through the majority of the population’s diet of energy-dense foods.6 Common diet practices of today have resulted not only in a growing number of people who are overweight and obese, but those same people are malnourished as well.6 (pg 3164s) What was once a very unrealistic outcome is now very common. The one thing that would have the greatest impact on improving our population’s health is also the one thing to which people rarely turn: a healthy, balanced, nutrient-dense diet. Instead, “answers” to their health problems are found in magazines and infomercials. The most basic concepts of eating healthy that most people were introduced to as children are often viewed as too simple to be effective. Ironically, simplicity has proven time and time again to be highly effective. Given the obvious reluctance of most people to eat healthier, it would seem to be easier to convince people to take a multivitamin mineral pill as assurance against ill health than to change their diet appreciably.6 (pg 3164s)

Given the growing amount of people who turn towards supplementation, it
becomes apparent that many of them take for granted the resilience of their kidneys. The kidneys are able to take a substantial amount of abuse before their functioning begins to decline. In fact, if one kidney is removed, the other will gradually increase in size in order to take on the extra workload. One way to look at the capabilities of the kidneys is to compare them to a sports car. A sports car may have the ability to go 200 mph, but it will rarely get to 100 mph. As for maintenance, chances are if someone owns a sports car, then he or she will not be putting chemicals in it that have even the smallest chance of damaging it. However, most people take the opposite approach for their own health. Poor food choices are constantly preferred over healthy ones. A common result of unhealthy eating is becoming overweight or obese, which in turn leads to other health issues like high blood pressure, high cholesterol, and type-2 diabetes. The two leading causes of chronic kidney disease are high blood pressure and type-2 diabetes, both of which can cause damage to the blood vessels in the kidneys, thus hindering their ability to efficiently clean the blood. The consequence that should be of most concern to athletes is that abnormalities in muscle function, exercise performance, and physical activity begin in earlier stages of chronic kidney disease and progressively worsen as ESRD ensues.7 Given that chronic kidney disease generally does not show any signs of it’s presence until later stages, an athlete noticing a decline in his or her performance may unintentionally cause more damage by using supplements as a solution to their problem.

There has always been confusion between what a person wants, as opposed to what they need. The belief held by many that supplements are what they “need”
to better their health and performance has put them at risk for potential kidney damage and other health problems. While supplements may be beneficial when used correctly, there is no need for an athlete consuming an adequate variety of food to pursue supplementation.2 (pg 2) In conclusion, from a comparative study of health and performance when dealing with an athlete’s choice of diet, it is apparent that a nutrient-dense diet is superior to supplementation for athletes, especially when comparing the relationship between supplementation and chronic kidney disease (CKD) and the effects each has on performance and health.

1. Ambrose P. J. Drug use in sports: a veritable arena for pharmacists. Medscape Today. 2010. Available at: medscape.com/viewarticle/487473. Accessed on March 28, 2010.

2. Rodriguez N. R., DiMarco N.M., Langley, S. Nutrition and athletic performance. Medscape Today. 2010. Available at: medscape.com/viewarticle/717046. Accessed on March 26, 2010.

3. Fink H. H., Burgoon L. A., Mikesky A. E. Practical applications in sports nutrition, 2nd ed. Sudbury, MA: Jones and Bartlett; 2009.

4. Metges C. C., Barth C. A. Metabolic consequences of a high dietary-protein intake in adulthood: assessment of the available evidence. J. Nutr. 2000; 130: 886–889.

5. Jones D., Borsheim E., Wolfe R. R. Arginine metabolism: enzymology, nutrition, and clinical significance. J. Nutr. 2004; 134: 2888S-2894S.

6. Ames. B. N. Free radicals: the pros and cons of antioxidants. J. Nutr. 2004; 134: 3164S-3168S.

7. Ikizler T., Himmelfarb J. Muscle wasting in kidney disease: let’s get physical. J Am Soc Nephrol. 2006; 17: 2097-2098.

8. Maillot M., Darmon N., Darmon M., Lafay L., Drewnowski A. Nutrient-dense food groups have high energy costs: an econometric approach to nutrient profiling. J. Nutr. 2007; 137: 1815–1820.

9. Greger J. L. Bioavailability of nutrients and other bioactive components from dietary supplements. J. Nutr. 2001; 131: 1339S-1343S.

10. Garlick P. J. Glutamine metabolism: nutritional and clinical signeifcance. J. Nutr. 2001; 131: 2556S-2561S.

04-27-2010, 03:42 PM
brb, not taking creatine