Henry C. Lukaski

As fall approaches, athletes world-wide begin training for interscholastic, intercollegiate and professional sports. The upcoming Sydney Summer Olympic Games to be held in October will surely raise the incentive of most athletes to prepare for their sports. They also raise concerns about the use of dietary supplements to boost athletic performance.

Creatine is one supplement that captured international prominence in the 1992 Barcelona Summer Olympic Games when two Olympic champions may have benefitted from its use. Their premier performances coupled with extensive media attention have led to a common perception that creatine supplementation is beneficial–even essential-- for victory in sports.

The widespread use of creatine extends from professional athletes to hopeful teenage athletes without an understanding of the relevant research. Consumption of creatine supplements during 1999 exceeded 2,800 tons with sales revenues exceeding $100 million per year! This staggering amount indicates an enormous expectation of potential benefit and fulfills the common athletic belief that if a little is good, then more is better.

Creatine is a nonessential dietary component found in abundance in meat and fish. The body also makes creatine by using other dietary components called amino acids. Creatine is transported into muscle and nerves where it is joined with phosphate to form phosphocreatine. Phosphocreatine can not leave a cell; instead it donates its phosphate to a partially depleted energy source. The transfer results in the fully loaded compound adenosine triphosphate (ATP) - the immediate supplier of energy for all cells, particularly muscle and nerve cells.

Having extra phosphocreatine in muscle cells helps to boost performance in many aspects of sport including jumping, sprinting and repetitions of these actions and thus to enhance performance in sports requiring either short-term all out effort or repeated stop and go activities. Athletes involved in sports like football, soccer, sprinting in track and swimming, basketball, and hockey may hike performance from increasing muscle phosphocreatine content. Phosphocreatine also may help athletes to recover from repeated heavy training session like pre-season training camps.

Two findings support increasing creatine intake. First, vegetarians have almost half the creatine concentration in their muscles as compared to meat-eaters. Supplementation with very large doses of creatine (20 to 30 grams daily equal to about 10 pounds of steak) elevates muscle creatine concentrations to maximal amounts. More recent research indicates, however, that much smaller doses of creatine (3 to 5 grams daily or 1 pound of beef) in excess of the usual intake of 2 grams are equally effective in elevating muscle creatine and phosphocreatine. Second, creatine supplementation of phosphocreatine-low muscles generally increases how hard and fast muscles work after refilling with phosphocreatine.

Here is the puzzle. Studies in research laboratories positively show that creatine supplementation enhances work performance during cycling, rowing and strength testing. In athletic contests, the results are mixed with no clear benefit of creatine supplementation on performance. Why? Most lab findings use healthy young men with mixed athletic ability and training status. Field studies, in contrast, focus on individuals who already perform near peak levels. Because age and sex affect how well creatine supplementation impacts muscle phosphocreatine contents, studies are needed with people of varying age and sex to evaluate the benefit of creatine supplementation on the average athlete.

Testimonial reports imply that creatine supplementation causes nausea, vomiting, diarrhea, kidney and liver problems, high blood pressure, and muscle cramps. The evidence, however, is not definitive. Creatine supplementation should be avoided by athletes who seek to lose weight while exercising heavily in hot and humid conditions. Preliminary findings indicate that creatine supplements may selectively reduce plasma volume which impairs the capacity to sweat and thus decrease the ability to maintain a normal body temperature during exercise in hot, steamy conditions.

Young athletes and pregnant women are cautioned against the use of creatine supplements. There is inadequate information on the safety of these products among anyone less than 18 years of age. Moreover, questions about the transfer of supplemental creatine from mother to fetus and accumulation of creatine in breast milk caution against the use of creatine supplements in pregnant and lactating women.

Because the Food and Drug Administration does not regulate creatine products, purity is a concern. Also, creatine-containing products, drinks and sport bars, may contain components, such as stimulants, that are banned by sport governing organizations. These products may be one example of "buyer beware"!

Some patients with specific clinical disorders that exhibit muscle wasting and premature muscle fatigue may benefit from treatment with creatine supplements. The supplements reportedly improve walking in patients with a variety of neuromuscular diseases and in those who have lost muscle mass and strength after orthopedic surgery. Thus, the supplements may have a role in the medical management of patients in such situations.

Although creatine burst on to the scene as a performance promoter for the physically gifted, questions about performance gains and safety concerns should temper its widespread use among athletes. Its promise of beneficial effects of creatine supplementation among patients with certain nerve and muscle disorders suggest new avenues of "performance enhancement". Creatine supplementation may be an example of adapting nutrition knowledge to meet new challenges.

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