Creatine is an amino acid made in the liver and stored in the muscles of the body.
This translates into greater gains in muscle mass, strength, and sprint performance during intense athletic training. The many scientific studies of creatine published over the past five years have found no deleterious effects or medical risk. While there have been some isolated anecdotal reports of negative side effects, such as decreased sexual functioning, there appears to be no credible evidence challenging its safety. One concern some researchers have is that with continuous supplementation the body might decline in its ability to produce creatine on its own. Some indirect evidence of this was found in a study with rats.