by Michael Nickels, M.D., Ph.D.
Several people have asked me recently about the dietary supplement creatine, its ability to boost athletic performance and any dangers that may be associated with its use.
When dealing with dietary supplements, it is always best to remember the caveat “let the buyer beware.” According to the Nutrition Business Journal, which provides market research for the dietary supplement industry, U.S. sales of pills, powders, bars, and beverages to boost athletic performance reached $1.26 billion in 1997. This market was expected to grow by 6–10% in 1998.
The sale of creatine, in particular, rose from $30 million in 1995 to an expected $200 million in 1998. Thus, the economic pressure to hype athletic benefits from dietary supplementation is enormous, and marketing claims typically range from exaggerations to outright lies.
Furthermore, since the dietary supplement industry is not regulated by the Food and Drug Administration, these substances are not subject to the same scientific and manufacturing scrutiny as medically prescribed drugs. While many vitamins, herbs and dietary supplements may be beneficial to our health and increase athletic performance, we should always maintain a certain degree of skepticism and not blindly buy into the industry hype. Decisions to supplement your diet with these substances should be based on an examination of the scientific literature and your supply should be purchased only from reputable sources.
This being said, what is the current evidence for and against the use of creatine to improve athletic performance?
Creatine is a peptide (small protein) made from the amino acids glycine, arginine and methionine. The average 70 kilogram male contains 120 grams of creatine, 95% of which is in skeletal muscle. Stores of creatine are maintained from ingestion of fish and meat products, as well as from production in the liver. Oral ingestion of excess creatine has been shown to reversibly inhibit its production in the liver and, once our skeletal muscles become saturated with creatine, the excess is filtered by the kidneys, then removed in the urine. Conversely, an absence of creatine from our diet, as occurs in strict vegetarians, results in suboptimal muscle concentrations, indicating that our liver is not capable of making all the creatine required for smoothly functioning skeletal muscles.
Our body stores energy for later use within the molecular phosphate bonds of ATP (adenosine triphosphate) molecules. When energy is required, a molecule of phosphorus is removed from ATP resulting in ADP (adenosine diphosphate), phosphorus, and energy. ATP is therefore similar to a battery in that it can supply energy on demand. Approximately 60–70% of muscle creatine is similarly phosphorylated, providing a second source of energy storage.
As our skeletal muscles deplete their stores of ATP during activity, the phosphocreatine molecules pass their stored energy to ADP, resulting in a rapid replenishment of ATP. The theory behind creatine supplementation is that by increasing our stores of phosphocreatine in skeletal muscle, more energy will ultimately be available during periods of exercise.
Most research studies indicate that creatine supplementation can improve performance in athletic endeavors requiring the use of explosive force over a period of a few seconds to a few minutes. The greatest benefit is likely to be for sports such as weight lifting, where repeated episodes of maximal exertion occur over short periods of time. Creatine is probably not beneficial to long duration aerobic exercises, such as distance running, since these activities utilize different biochemical pathways following depletion of ATP stores. Furthermore, the effects of creatine supplementation have been found to be highly variable among individuals, with maximum performance boosts being only about 5%.
Creatine does not directly promote increased muscle mass, other than providing extra energy to possibly get one more repetition. Initial weight gain with creatine use is typically secondary to increased water retention within skeletal muscle.
Short-term use of supplementary creatine within recommended guidelines (loading phase of 20–25 grams a day for 6 days, then 2 grams per day) is generally considered to be safe. The effect of long-term use, however, is unknown.
Dehydration is a potential problem, and one should be sure to consume plenty of fluids during use of supplemental creatine, especially during the hot summer months. Most reports of adverse consequences associated with its use have come from competitive wrestling, were dehydration secondary to fluid restriction is common in an effort to “make weight.”
It should also be noted that creatinine, a breakdown product of creatine, is used by physicians to evaluate renal function, as increased blood levels may indicate varying degrees of kidney failure. If your doctor starts talking about renal disease, be sure to tell him you are taking supplemental creatine, or you may find yourself in the middle of an expensive kidney disease work-up that could include a renal biopsy (sampling of kidney tissue).
In conclusion, although creatine is generally considered to be one of the “safer” athletic dietary supplements, unless you are in the top 1% of competitive athletes competing in activities requiring explosive exercise, you would be better served to improve performance through skill development, sweat and improved diet. Creatine is a very expensive way to get a small return on performance.
If you’re not among the “best of the best,” the person you are probably helping most is the chairman of the board of the company who sold you the product in the first place.
Michael Nickels received an M.D. and a Ph.D. in Biomedical Science (Microbiology and Immunology) from the University of South Carolina School of Medicine.