As of 2011, there was no clearly established scientific connection between creatine and cancer. Creatine, a naturally occurring amino acid that athletes sometimes take as a dietary supplement, has at various times been reported to cause cancer or to cure cancer. None of these claims have been sufficiently backed up by credible scientific research though.
Creatine is an amino acid involved in anaerobic or "power" exercise, such as weightlifting and other high-intensity, short-duration activities. Most of the creatine that a person needs is created naturally by the kidneys, with some being taken in by eating fish, wild game or lean red meat. Creatine supplements, usually in the form of a powder, are marketed to improve athletes' performance in some activities, but the effectiveness of these supplements varies widely from person to person.
A report published in the early 2000s indicated that creatine supplements might cause kidney cancer, but this report has been largely discredited. Research has not conclusively disproven any relationship between creatine and cancer risk, but there is also no significant reason to believe the two are linked. There are no documented cases of it leading to increased risk of cancer in either humans or animals. In fact, a few subsequent studies have shown that taking creatine might actually decrease a person's chances of getting cancer, but as of 2011 there was not yet enough evidence to substantiate this research.
In the mid-1900s, a creatine-derived treatment known as Krebiozen was marketed to treat cancer. It was never submitted for clinical trials in the US, however, because there was no evidence linking creatine and cancer cures. This remedy has also been discredited by the scientific community as a whole.
Since creatine has been shown to increase muscle mass in many athletes, it has been proposed as a treatment to stop cancer patients from losing muscle mass during chemotherapy treatment. This is not a direct link between creatine and cancer, however, since the creatine is being used to treat the side effects of the treatment, rather than the illness itself. As of 2011, more research is still needed in order to determine whether cancer patients could benefit from this use of creatine.