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Q: I am an avid runner with a desire to improve my performance. In some of the athletic stores and in magazines I have read advertisements for a performance, enhancing supplement called creatine. What is this supplement, what amounts are generally taken, and are there side effects associated with creatine supplementation? |
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A: Creatine supplementation has become popular by a variety of athletes due to the notion that it can enhance muscle performance. In a limited number of research studies oral creatine supplementation has been shown to enhance performance during repeated bursts of stationary cycling and weight lifting. However, the limited research for running and swimming has not demonstrated a clear benefit of oral creatine supplementation on performance. This may be in part due to weight gain associated with creatine usage, which may negatively affect performance.
The rationale for taking creatine supplements is that it will increase muscle phosphocreatine, the energy producing form of the amino acid creatine, which may enhance muscle energy, delay fatigue, and possibly improve muscle mass. Creatine is an amino acid found in the diet (meats and fish), taken as a dietary supplement (creatine monohydrate), or made endogenously by the liver, kidneys, and pancreas. "Normal" diets contain about 1-2 g/day of creatine with less being consumed by vegetarians. Creatine is stored in the skeletal muscle, heart, kidneys, and brain.
In the muscles creatine exists in different forms including creatine, phosphocreatine and creatinine. During high-intensity short burst of exercise the muscle uses phosphocreatine to generate ATP, the bodies source of energy, for muscle contraction and power. Consuming creatine supplements has been shown to increase the amount of phosphocreatine in muscle, improved regeneration of phosphocreatine during recovery, and may increase muscle mass. Therefore, increasing muscle phosphocreatine can aid in providing energy during short burst of activity and may prevent muscle fatigue.
Unfortunately, there are no clear guidelines for creatine supplementation. However, in a survey of dosing of male college athletes an initial loading phase for 2 to 5 days of a 20 g/d (0.3 g/kg body weight) dose, which is followed by a maintenance dose of 2 g/d (0.03 g/kg body weight) has been reported. Exceeding the dosing regimens has not been shown to further enhance maximum muscle creatine concentrations. Furthermore, muscle phosphocreatine levels return to baseline after ~28 days after cessation of creatine supplements.
The reported adverse effects include weight gain (e.g. 2-5 pounds during loading phase), muscle cramping, gastrointestinal disturbances (e.g. diarrhea and gastrointestinal cramping), increased risk of dehydration, and impairment of kidney function. Moreover, there are limited studies documenting the long-term effects of oral creatine supplementation on other organs such as reproductive organs, heart, or liver.
In summary, oral creatine supplementation may enhance performance during short bursts of high-intensity exercise such as stationary cycling or weight lifting. Limited studies reveal a positive benefit of creatine supplementation on enhancing running performance, likely due to weight gain associated with supplementation. As with many dietary supplements that claim to have ergogenic or other health benefits more research is needed in order to better understand both the positive benefits and potential side effects of short and long-term supplementation. Therefore, when considering taking oral protein supplements it is recommended to consult with your physician or sports medicine professional to discuss usage.
References and Web Resources:
Juhn, MS: Oral Creatine Supplementation, Separating Fact from Hype. 27(5): 232-234,1999. http://www.physsportsmed,com/issues/1999/05_99/juhn.htm
Juhn,, MS, O’kane JW, Vinci DM: Oral creatine supplementation in male collegiate athletes: a survey of dosing habits and side effects. J Am Diet Assoc 99(5): 593-595, 1999.
Juhn MS, Tarnopolsky M: Oral Creatine supplementation and athletic performance: a critical review. Clin J Sports Med 8(4):286-297, 1998.
United States Department of Health and Human Services, Office of Disease Prevention and Health Promotion, Washington, DC: Dietary Supplement Health and Education Act of 1994 (DSHEA 1994): Public Law 103-417). http://web.health.gov/dietsupp/toc.htm |
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Rebecca L. Persinger, RD, CNSD, PhD
Rebecca is active in the Seattle running and cycling communities and enjoys other outdoor activities including: snowshoeing, skiing, mountain biking, and hiking.
Dr. Persinger bio |
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