Creatine: Separating Fact from Hype
August 1, 1999 4 minutes read
Creatine: Separating Fact from Hype
Abstracts & Commentary Synopsis: The potential risks and benefits, historical perspective, site of action, means of excretion, and suggested dosing protocol of the dietary supplement.
Sources: Volek JS. What we now know about creatine. ACSM’s Health and Fitness Journal 1999;3:27-33; Juhn, MS. Oral creatine supplementation: Separating fact from hype. Phys Sports Med 1999;27:47-56.
The articles on creatine by volek and juhn provide an excellent review of the historical perspective, site of action, means of excretion, and suggested dosing protocols, as well as potential risks and benefits of this dietary supplement. The sports world’s recent enamorment with creatine as an ergogenic aid was spurred by the 1992 report of Harris and colleagues1 in which they showed that muscle creatine could be significantly and rapidly increased by ingesting creatine monohydrate. The following responses provide highlights from these articles.
What is Creatine?
Creatine is a nitrogenous amino acid found primarily in skeletal and heart muscle, brain, testes, and retina. According to Volek, a Penn State registered dietician and exercise physiologist as well as co-author of the American College of Sports Medicine’s Current Comment statement on "Creatine Supplementation,"2 95% of all creatine is found in skeletal muscle primarily as phosphocreatine.
Why is Creatine Important?
Creatine and phosphocreatine play important roles in anaerobic energy production by participating in the reversible creatine kinase reaction that acts not only to replenish ATP during intense exercise but also to resynthesize phosphocreatine during periods of rest, as depicted in the following reaction:
Creatine Phosphate
Phosphocreatine + ADP + H+ ATP + Creatine
ATP = Adenosine Triphosphate
ADP = Adenosine Diphosphate
H+ = Hydrogen Ion
Phosphocreatine, because it produces a large amount of ATP per unit of time, functions as a temporary energy buffer during periods of rapid ATP turnover such as occurs with repeated bouts of intense activity.
What is the Body’s Source of Creatine?
The body synthesizes 1-2 grams of creatine each day (the normal daily requirement) in the liver, kidneys, and pancreas. Additional dietary sources of creatine (primarily from fish and meats) are used to enhance the body’s production of creatine and phosphocreatine. Storage of creatine and phosphocreatine in skeletal muscle is limited but, as data from Harris et al demonstrated, storage of creatine and phosphocreatine can be significantly increased by diet supplementation with oral creatine monohydrate.
How Much Creatine is Needed to Enhance Muscle Stores?
Juhn, a frequent lecturer on creatine and a clinical instructor at the University of Washington, suggests a dosing schedule of a loading dose of 20 grams of creatine each day for five days followed by a maintenance dose of 2 grams per day. Others have suggested 2-5 grams a day as a maintenance dose. Juhn also states that if one does not wish to use high loading doses, "3 grams per day of creatine for 28 days results in muscle creatine concentrations similar to 5 days of loading." Furthermore, he emphasizes that following loading, excessive daily doses of creatine are of no additional benefit, as muscles have a saturation limit and additional creatine will only be excreted in the urine.
Creatine supplementation can increase muscle phosphocreatine concentration by 6-16%, according to Juhn, and muscle’s total creatine (creatine + phosphocreatine) by up to 20%. Muscle storage of creatine is variable during the loading dose, but both Juhn and Volek suggest ingesting large amounts of glucose during creatine loading can be used to enhance creatine accumulation.
Why is Creatine Considered an Ergogenic Aid?
Creatine supplementation appears to enhance some repeated short-burst, high-energy activities (e.g., repeated sprints on a stationary bike). This seems logical since creatine supplementation increases muscle stores of phosphocreatine, increasing availability of phosphocreatine for energy production. However, data on the performance-enhancing effects of creatine supplementation are conflicting. Some feel the variability of creatine accumulation within muscles following supplementation is responsible for these variable reports. More research is needed, according to both Juhn and Volek.
Are There Any Adverse Effects to Taking Creatine Supplements?
Although no definite adverse effects of creatine supplementation have been proven, side effects such as dehydration, GI distress, muscle cramping, and nausea and vomiting have been reported. Concern has also been raised regarding liver and renal dysfunction. The effect of creatine supplementation on brain or testicular creatine is unknown. The articles by Juhn and Volek provide excellent discussions on the risks and benefits of creatine supplementation.
Comment by Letha Y. Griffin, MD, PhD
Since the time of the ancient Greeks and probably before, athletes have been looking for an edge, a way to enhance normal energy-producing pathways in order to push physiologic limits. Excess vitamins, hormones, oxygen, red cells, metabolic substrates, cofactors, and many other sport enhancers have risen and fallen in popularity. Creatine can be added to this list. Reading comprehensive reviews such as these two articles will help medical personnel stay abreast of current controversies surrounding this potential ergogenic aid.
References
1. Harris RC, et al. Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clin Sci (Colch) 1992;83:367-374.
2. Kraemer WJ, Volek JS. Creatine supplementation current comment. Clin Sports Med 1999;18:651-666.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content