Creatine is a nitrogen-containing organic acid that is synthesized by the body and stored primarily in muscle tissues in the form of phosphocreatine (also known as creatine phosphate). Phosphocreatine aids in energy production by donating phosphate to ADP to make ATP, the principal source of energy for muscle tissues. In addition to that which is manufactured within the body, small amounts of creatine may be obtained through the diet, primarily in foods high in animal protein such as meat and fish. Creatine is also available as a dietary supplement in the form of creatine monohydrate.
Creatine supplements are used primarily by athletes, weight lifters, and body builders who wish to increase muscle strength and lean muscle mass. Many small-scale studies indicate that creatine supplementation can increase lean body mass and muscular strength and improve performance in high-intensity, short-duration exercises. However, other studies failed to show performance enhancement in well-trained athletes, and creatine does not appear to improve endurance performance or aerobic exercise capacity. Due to small test-group size and inconsistent results, larger studies are needed before the effects of supplemental creatine can be determined.
Studies with positive results have generally used 20 grams of creatine monohydrate per day for at least 5 days. Smaller doses or shorter periods of administration may not be sufficient to significantly raise muscle phosphocreatine levels. Creatine has very low toxicity and appears to be well tolerated at this dosage range; however, the long-term effects of creatine supplementation are unknown at this time.