Creatine
Creatine is a natural substance made in our bodies and also found in meat and fish. In muscle, creatine is used for high-intensity contractions. Creatine is stored in muscle cells as creatine phosphate, a compound that can provide quick energy to working muscles.
Proposed performance-enhancing properties
The idea behind creatine supplements is to increase the resting levels of creatine phosphate in the muscle cells, thus theoretically increasing the amount of energy available for high power output. A higher power output would delay fatigue and improve performance in short duration high intensity exercises such as sprinting or weight lifting [1].
Scientific evidence
Studies show that creatine supplementation of approximately 20-25 g/day for several days increases creatine levels in the muscle tissue by 20% (more so in people who had a lower creatine store to begin with) [2]. These levels will be sustained by taking 3 g per day thereafter.
Many studies show that creatine supplementation increases power output in exercise involving repeated bouts of high intensity activity such as sprinting, high velocity sprinting and knee extensions [3,4,5].
However, a careful review of all the research to date concluded that these ergogenic effects, when found, were in untrained subjects performing several exercise bouts under laboratory conditions. Highly trained athletes, on the other hand, did not appear to benefit from creatine supplementation. Therefore, the use of creatine to improve competitive performance does not seem to be justified [6].
Cautions and side effects
Studies have reported a gain in body weight during creatine supplementation [3], probably due to an increase in muscle water content.
Anecdotal evidence suggests that muscle cramping and intestinal discomfort also occur with creatine supplementation, yet published research does not support these effects.
There is a distinct lack of scientific data on the safety of creatine when taken by children and pregnant or breast feeding women. If you fit into these categories do not take creatine.
As with all dietary supplements, make sure that you inform your physician of what you are taking.
Points to Consider
Be aware that purity of creatine supplements is not guaranteed by law.
Creatine is usually marketed under the name of creatine monohydrate. All creatine monohydrate is the same chemically, so the cheapest brand is probably as good as a more expensive brand.
References
1. Eichner ER: Ergogenic aids: what athletes are using and why. The Physician and Sport Medicine 25:4 April 1997.
2. Harris R, Sutherland K, Hultman E.: Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clinical Science 83:367-374, 1994.
3. Greenhaff PL, Bodin K, Soderlund K, Hultman E.: The effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis. Am. J. of Physiol. 266:E725-E730, 1994.
4. Maughan RJ.: Creatine supplementation and exercise performance. Int. J of Sport Nutr. 5:94-101, 1995.
5. Volek JS. Creatine supplementation and its possible role in improving physical performance. ACSM's health and fitness journal. 1(4):23-29, 1997.
6. Mujika I, Padilla S: Creatine supplementation as an ergogenic aid for sports performance in highly trained athletes: A critical review. Intern. J of Sports Med., Vol.18, No.7, pp.491-496, 1997.