Despite the anecdotal claims concerning the negative effects of creatine supplementation, the evidence supports the claim that creatine supplementation is safe. In the past, there have been claims that creatine supplementation can cause gastrointestinal problems and muscle cramping, but it is quite possible that there were additional factors involved that caused these adverse reactions. Kim, Kim, Carpentier, and Poortmans’ review study on the safety of creatine supplementation found that creatine supplementation (20g/day) has no effect on liver or kidney function. Additionally they dispelled claims that creatine could have a potential carcinogenic effect. According to their study, the only people at risk for adverse health effects from creatine supplementation are those with preexisting renal disease or persons with a condition which puts them at risk for renal dysfunction (i.e. diabetics, hypertension, metabolic disease, etc.)
Faraji et al. examined a group of 21 year old collegiate males to see if six days of creatine supplementation would improve their athletic performance in the 100 and 200 meter sprint. They found a significant increase in 100m time from the creatine group, but did not find a significant increase in the 200 meter time. They concluded that the 200 meter time did not improve as much due to the participants not having enough time to develop the proper running mechanics. The evidence from the improvement of the 100 meter time supports past studies which claim that creatine supplementation will improve athletic performance.
Faraji et al. discussed previous studies’ claim that creatine supplementation does not improve athletic performance. What the group found was that professional or semi-professional athletes were used in these studies. They concluded that in well-trained athletes their muscles have already achieved the maximum creatine uptake level. Regardless of how much additional creatine they add to their diet, it is not possible for their muscles to store any more. In amateur athletes and untrained populations, it is possible for their muscles to uptake much more creatine due to them not hitting their maximum level, and therefore, people who have not reached their full athletic potential can still benefit from creatine supplementation.
Kim, H., Kim, C., Carpentier, A. A., & Poortmans, J. (2011). Studies on the safety of creatine supplementation. Amino Acids, 40(5), 1409-1418.
Faraji, H., Arazi, H., Vatani, D., & Hakimi, M. (2010). THE EFFECTS OF CREATINE SUPPLEMENTATION ON SPRINT RUNNING PERFORMANCE AND SELECTED HORMONAL RESPONSES. / Die effek van kreatienaanvulling (of supplementasie) op naelloopprestasie en geselekteerde hormonale response. South African Journal For Research In Sport, Physical Education & Recreation (SAJR SPER),32(2), 31-39.