Physical Training July 2002

Metabolic Stimulants: Pyruvate, Carnitine and Creatine Science or Trend?

By Sarah Sakhuja
Copyright © Sarah Sakhuja 2002. All rights reserved.

A balanced diet, exercise and simplistic healthy lifestyles are becoming obsolete.  Nowadays, there seems to be a movement towards new, complex and trendy exercise and diet choices.  Expanding on these trends, oral supplementation over the last ten years as a means of weight loss, endurance or power enhancement has soared with increasing availability and frequency of use.  However, many individuals fail to take the time to question the validity or even the safety of such “miracle drugs.” In an effort to look critically at a few of the metabolic stimulants currently on the market, I have chosen to focus on three popular oral supplements: pyruvate, carnitine and creatine.

Pyruvate is a word that when casually incorporated into conversation at the gym can make an individual sound intelligent and dedicated to their physical enhancement.  Pyruvate is the end product of glycolysis in aerobic respiration, and will ultimately be converted to acetyl-CoA by pyruvate dehydrogenase before entering the mitochondria, forming ATP.  Pyruvate supplementation has often been implemented as a weight loss tool by shifting metabolic gradients, making the body “energetically wasteful” (Dyck lecture notes).  By adding pyruvate to the muscle it will theoretically cycle back to reduce its concentration, burning ATP in the process and thus increasing the energy used by the body.  (Dyck lecture notes).  Interestingly, Stanko et al. (1990) found a 20% increase in arm crank performance following supplementation.  However, in more recent studies there have been no significant results, including no findings of increased performance or blood concentration of pyruvate (Morrison et al. 2000).  Furthermore, many individuals complain of gastrointestinal discomfort including severe bloating and cramping as a common side effect of pyruvate use (Dyck lecture notes).  As an aside, pyruvate users have provided little anecdotal evidence of performance enhancement, and spend a large amount of time dealing with side effects that will leave them blaming the dog.

Carnitine has recently emerged into the lives of many athletes and gym junkies alike.  Carnitine, needed for free fatty acid transport in the body, is provided by foods such as meat and dairy products, or is made endogenously by the liver..  Its proposed mechanism is that increased concentrations of carnitine in the muscle will increase free fatty acid transport into the mitochondria by acting as a buffer to lower acetyl-CoA concentration..  It is thought that this will decrease the use of carbohydrate and glycogen within the body, reducing the rate of fatigue and increasing the duration of exercise..  However, what is interesting is that carnitine supplementation has been shown to stimulate carbohydrate metabolism instead of inhibiting it (Dyck lecture notes).

Creatine use has entered our lives through health food and gym promotions, as well as “natural food products.”  On a recent hot and humid day, I was asked at a juice stand if I would like to add a “booster” to my drink. One of the options advertised as a power and energy kick contained none other than creatine.  Statistics show that a high percentage of the North American athletic population consumes oral doses of creatine on a daily basis (McGuine et al. 2001).  In a recent publication, 37 public high school football teams were questioned regarding their creatine use.  Grade 12 players had the highest proportion of users at 50.5%, most of them attributing an enhanced recovery following workouts to their use. The danger in this situation is a high percentage of users who are unlikely to understand the metabolic actions of creatine and its subsequent side effects.  The researchers stress the need for education and guidance with respect to its uses, doses, benefits and risks (McGuine et al. 2001).

creatine kinase pathway

Creatine is part of an important metabolic cascade required for anaerobic production of energy.  ATP concentration within the muscle can sustain an energy demand during exercise for less than one second (Stryer 1995).  For this reason both skeletal and cardiac muscle contain a pool of high energy in the form of creatine phosphate, which can transfer phosphate bonds to ADP.   It is this reaction that provides a substantial source of energy in the first four seconds of exercise (Stryer 1995).  It is thought that increasing the intracellular concentration of creatine within the muscle will play a significant role in boosting this anaerobic pathway (Hespel et al. 2001).  In fact oral creatine supplementation can increase the intramuscular concentration of creatine within the body, providing positive results for its users.  Furthermore, research is currently being conducted focusing on the relationship between creatine use and the prevention of muscle atrophy (Hespel et al. 2001).  What is scientifically significant is the performance increases associated with intermittent high-intensity resistance exercise (Balsom et al. 1993; Hespel et al. 2001; Volek et al. 1997).  Furthermore, increases in body weight measurements have been recorded with creatine use (Balsom et al. 1993; Hespel et al. 2001; Volek et al. 1997).  However, endurance exercisers cannot attribute performance increases to such supplementation, as creatine use seems to be restricted to short term endurance (Balsom et al. 1993).

As I am not disputing the obvious advantages and positive attributes of creatine use, it is the side and long term effects that must be investigated.  The scientific community agrees that caffeine significantly counteracts the positive effects of creatine use (Vandenberghe et al. 1996).  Therefore, the many individuals who take this supplement without significant education and comprehension may completely counteract any positive effects with the use of caffeine, a staple in most North American diets. Also, estimations of increased body mass could be attributed to an increase in water retention due to the rise of the intracellular concentration within the muscles.  In a recent study, skinfold measurements and therefore fat composition did not change following supplementation, despite an increase in mass (Volek et al. 1997).  This leads to the question of kidney involvement and urine excretion.  Approximately half of the oral creatine is excreted within the urine, suggesting potential harm to the kidneys with long-term creatine supplementation and excretion (Burke et al. 2001).  It has also been suggested that creatine use over long periods of time could contribute to an increase in cancer rates.  However, at this time there is insufficient evidence linking cancer and creatine use (Hespel et al. 2001).  This indicates the need for research regarding long-term creatine use on the human body.  Although we can see short-term performance enhancement, long-term effects have not been verified or fully documented.

It is important to stress the fact that although I do not support the use of such supplementation, it is not valid to say that none of these substances have scientific validity.  I am positive that many users would have an abundance of personal testimony indicating their own success stories.  However, what I do know is that any benefits present do not negate the risks and discrepancies associated with both short and long-term ingestion.

In conclusion the only scientific certainty associated with a healthy lifestyle is a nutritious diet and regular exercise.  It is important for society to include these two components as the foundation of their lifestyle until further research on pyruvate, carnitine and creatine emerges.

Works Cited

      Balsom, P.D., Harridge, S.D.R., Söderlund, K., Sjödin, B., Ekblom, B.  1993.  Creatine supplementation per se does not enhance endurance exercise performance.  Acta Physiol. Scand.  149: 521-523.
      Burke, D.G., Smith-Palmer, T., Holt, L.E., Head, B., Chilibeck P.D.  2001.  The effect of 7 days of creatine supplementation on 24-hour urinary creatine excretion.  J Strength Cond. Res.  15(1): 59-62.

      Dyck, D.  2001.  Lecture Notes; Nutrition Exercise and Metabolism.  November 6.  University of Guelph.

      Hespel, P., Eijnde, B.O., Derave, W., Richter, E.A.  2001. Creatine Supplementation: Exploring the Role of the Creatine Kinase/Phosphocreatine System in Human Muscle.  Can. J Appl. Physiol.  26(Suppl.): S79-S102.
      McGuine, T.A., Sulivan, J.C., Bernhardt, D.T.  2001.  Creatine supplementation in high school football players.  Clin. J Sports Med.  11(4): 247-253.

      Morrison, M.A., Spriet, L.L., Dyck, D.J.  2000.  Pyruvate ingestion for seven days does not improve aerobic performance in well-trained individuals.  J Appl. Physiol.  89(2): 549-556.

      Stanko, R.T., Robertson, R.J., Spina, R.J., Reilly J.J. Jr., Greenawalt, K.D., Goss, F.L.  1990.  Enhancement of arm exercise endurance capacity with dihydroxyacetone and pyruvate.  J Appl. Physiol.  68(1): 119-124.

      Stryer, L.  1995.  In Biochemistry.  W.H. Freeman & Company, New York.  pp. 447-448.
      Vandenberghe, K., Gillis, N., Van Leemputte, M., Van Hecke, P., Vanstapel, F., Hespel, P.  1996.  Caffeine counteracts the ergogenic action of muscle creatine loading.  J Appl. Physiol.  80(2): 452-457.

      Volek, J.S., Kraemer, W.J., Bush, J.A., Boetes, M., Incledon, T., Clark, K.L., Lynch, J.M.  1997.  Creatine supplementation enhances muscular performance during high-intensity resistance exercise.  J Am. Diet. Assoc.  97(7): 765-770.

Sarah Sakhuja holds a BSc. in Human Kinetics from the University of Guelph
Physical Training July 2002