Creatine: little impact on athletic performance, but a risk of adverse effects

(1) Creatine occurs naturally in the body. Some is derived from dietary sources, but endogenous synthesis covers individual requirements. Creatine deficiency occurs only in subjects with genetic disorders. (2) Oral creatine supplementation at supraphysiological doses seems to slightly improve the performance of some types of muscle exercise, but only those lasting less than 30 seconds; even this small effect is inconsistent. (3) The vague regulatory status of creatine supplements hinders effective monitoring of adverse events. Serious adverse events have been reported in people taking creatine supplements, but it's still unclear whether or not the creatine is responsible. Animal data suggest a link with cancer after long term exposure. (4) The precise composition of creatine supplements is unclear: contamination is possible, and other substances, especially doping agents, are sometimes added. (5) Taking creatine supplements is inadvisable.