Potential side effects of oral creatine supplementation: A critical review

Objective: To critically review the current data concerning potential safet y concerns of oral creatine supplementation. Data sources and study selection: Medline was searched using keywords to lo cate published works relating to creatine supplementation and adverse effec ts. Abstracts that specifically studied potential adverse effects of creati ne were also utilized, as were human and animal studies of creatine metabol ism in various organ systems. Data extraction and synthesis: Specific data from studies that investigated creatine's side effects and metabolism were grouped by organ system to bet ter describe potential safety issues. Conclusions: Creatine supplementation results in weight gain due to water r etention, which may impede performance in mass-dependent activities such as running and swimming. Although short-term use (fewer than 28 days) at reco mmended doses has not been shown to cause significant adverse effects, the studies on which this is based involved small numbers of subjects, and none of the studies provided a sample size calculation. Furthermore, despite th e fact that creatine is normally found in cardiac muscle, brain, and testes , these areas remain essentially unstudied with respect to oral creatine su pplementation. Future studies should include large randomized controlled tr ials evaluating the short and long term effects of oral creatine supplement ation on the renal and hepatic systems, as well as the many other organ sys tems in which creatine plays a metabolic role.