Creatine; Does it Work?

Sports Science Exchange 91 Supplement

VOLUME 16 (2003) NUMBER 4

Creatine: Does It Work?

When athletes consume creatine in their diets, whether from meat and fish or from creatine supplements, some of the creatine will be absorbed from the blood into the muscles. Once in the muscles, creatine can be combined with phosphate to form phosphocreatine, a vital�but very limited�source of energy for brief, high-power activities such as sprinting and resistance training. It follows that creatine users should have more phosphocreatine energy available to perform these kinds of activities, leading to improved performance.

This rationale for consuming creatine supplements sounds great, and many millions of dollars worth of creatine supplements are sold every year. But even after the completion of several hundred scientific investigations, many questions remain about the value of creatine supplementation for performance of various sports and about how much and when to use creatine�if it should be used at all. Here is some of what is known:

Supplementing the diet with 20 grams of creatine daily (four 5-gram doses) for 4-5 days (i.e., "creatine loading") will increase muscle levels of creatine in some, but not all, individuals. Doses of 5 grams raise blood creatine concentrations to the optimal amount that will maximize uptake of creatine into muscles. Creatine ingested in amounts greater than 20 grams per day will be wasted in the urine.
Ingestion of 2 grams of creatine daily for 30 days takes longer but is just as effective as creatine loading for increasing the creatine concentration in muscle.
Carbohydrates consumed with creatine supplements will increase creatine uptake by muscles compared to creatine supplements alone, but not by much.
Creatine ingestion will likely increase body mass by a few pounds or kilograms, some of which will be extra muscle and the rest extra water. This weight gain could be detrimental in sports like running in which additional body weight may impair performance.
Because creatine can make muscles appear larger by increasing the muscle uptake of water, it may enhance motivation to perform better and work harder in sports where increased muscle mass is desirable.
Most laboratory studies of high-power tests lasting 30 seconds or less show slight, but potentially important improvements in performance in creatine users. A common example of such performance tests is repeated bouts of maximal cycling exercise, each bout lasting about 6-10 seconds.
With laboratory performance tests that last between 30 and 90 seconds, the evidence for creatine effects on performance is predominantly positive, but is less persuasive than for activities lasting less than 30 seconds.
As test durations exceed 90 seconds, it is progressively less likely that creatine users will perform better than non-users (Table 1S).

TABLE 1S. Evidence that Supports or Refutes an Ergogenic Effect of Creatine for Various Performance Tests

Performance Test	Evidence for Ergogenic Effect
Intense Brief Exercise (Laboratory Tests; <30 sec)	Convincing
Weight-lifting (when creatine is used concurrently with resistance training)	Convincing
Intense Exercise (Laboratory Tests; 30 sec to 3 min; intermittent effort)	Moderately Convincing
Convincing Intense Exercise (Laboratory Tests; >3 min)	Not Convincing
Intense Exercise (Field Tests such as Swimming and Sprinting)	Not Convincing

When consumed in moderate doses, there seem to be no adverse effects of creatine supplementation in healthy adults.
Scientists do not know the effects of creatine supplementation on children who are still growing. Individuals younger than 18 years of age should not take creatine supplements.
Because the Food and Drug Administration does not tightly regulate supplements, there is no guarantee that all the ingredients in a product are stated on the label. There have been incidents where supplements are "spiked" with stimulants or prohormones that are banned by sport governing bodies.
Don't count on supplements to make you a champion. Using any supplement, including cratine, can never take the place of hard training and skill practice, good nutrition, sound sleep, and ample rest.

SUGGESTED ADDITIONAL RESOURCES

Branch, J.D. (2003). Effect of creatine supplementation on body composition and performance: a meta-analysis. Int. J. Sport Nutr. Exerc. Metab. 13:198-226.

Kreider, R.B. (2003). Effects of creatine supplementation on performance and training adaptations. Mol. Cell. Biochem. 244:89-94.

Preen, D., B. Dawson, C. Goodman, J. Beilby, and S. Ching (2003). Creatine supplementation: a comparison of loading and maintenance protocols on creatine uptake by human skeletal muscle. Int. J. Sport Nutr. Exerc. Metab. 13:97-111.

Rawson, E. S. & Volek, J. S. (2003). The effects of creatine supplementation and resistance training on muscle strength and weight-lifting performance. J. Strength Cond. Res. 17, 822-831.

Terjung, R.L., P. Clarkson, E.R. Eichner, P. Greenhaff, P.J. Hespel, R.G. Israel, W.J. Kraemer, R.A. Meyer, L.L. Spriet, M.A. Tarnopolsky, A.J. Wagenmakers, and M.H. Williams (2000). American College of Sports Medicine roundtable. The physiological and health effects of oral creatine supplementation. Med. Sci. Sports Exerc. 32:706-717