Side effects and adverse reactions to creatine supplementation
Short term (less than 2 weeks) exercise studies have not reported any adverse events associated with creatine supplementation. There have been no long term studies done to evaluate the safety of prolonged administration. This is unfortunate because increasingly more and more athletes are taking creatine supplements for longer periods. Anecdotal reports have begun to emerge and have noted increased muscle cramping (especially during exercise in the heat), nausea and other gastrointestinal disturbances, elevated liver transaminases, and acute renal injury.
Creatine supplementation, in the dosages commonly used, results in urinary concentrations that are 90 times greater than normal. The long term effects of this have not been investigated, but there is possibility for a variety of nephrotoxic, i.e., kidney damaging, events. There is potential for direct toxicity on renal tubules where urine is formed, and for acceleration of kidney stone formation. Recently, a baseball player for the Houston Astros was determined to have suffered from dehydration, kidney stones, and transient kidney damage as the result of creatine supplementation. Additionally, the deaths of 3 collegiate wrestlers this past year are being investigated to determine what role creatine supplementation may have played.
Impurities are present in virtually every manufactured product, and in some cases, even though the product may be considered harmless, the impurity is not. Such was the case in the late 1980's when an epidemic of cases of eosinophilia-myalgia syndrome, including over 30 deaths, were blamed on a contaminant present in L-tryptophan (9), an amino acid supplement widely taken as a sleep aid. Creatine, and other such supplements, are not regulated by the FDA. No published investigation has been conducted on creatine to determine what impurities might be present in creatine supplements, and what their long term effect might be.
The bottom line is that no one can confidently state that prolonged creatine supplementation is safe, and its use would best be avoided until more data can be compiled. Prolonged administration is, in essence, an uncontrolled toxicity study and one which might yield harmful results. Is it worth the risk? Remember, it's your body!