The vast amount of data on creatine and exercise performance does not support the dramatic claims of muscle building and power development by manufacturers.
- Tex Med 2002 Feb;98(2):41-6 -- Performance-enhancing substances in adolescent athletes. -- Gomez JE.

Documented side effects induced by creatine monohydrate are weight gain; influence on insulin production; feedback inhibition of endogenous creatine synthesis; long-term damages on renal function. 

A major point that related to the quality of creatine monohydrate products is the amount of creatine ingested in relation to the amount of contaminants present. During the industrial production of creatine monohydrate from sarcosine and cyanamide, variable amounts of contaminants (dicyandiamide, dihydrotriazines, creatinine, ions) are generated and, thus, their tolerable concentrations (ppm) must be defined and made consumers known. Furthermore, because sarcosine could originate from bovine tissues, the risk of contamination with prion of bovine spongiform encephalopathy (BSE or mad-cow disease) can't be excluded. Thus, French authorities forbade the sale of products containing creatine.
- J Sports Med Phys Fitness 2001 Mar;41(1):1-10 -- Creatine as nutritional supplementation and medicinal product. -- Benzi G, Ceci A.

Despite numerous publications on the ergogenic effects of this naturally occurring substance, there is little information on the possible adverse effects of this supplement. Gastrointestinal disturbances and muscle cramps have been reported occasionally in healthy individuals. 

Liver and kidney dysfunction have also been suggested on the basis of small changes in markers of organ function and of occasional case reports, but well controlled studies on the adverse effects of exogenous creatine supplementation are almost nonexistent. 

Idiosyncratic effects may occur when large amounts of an exogenous substance containing an amino group are consumed, with the consequent increased load on the liver and kidneys. Regular monitoring is compulsory to avoid any abnormal reactions during oral creatine supplementation.
- Sports Med 2000 Sep;30(3):155-70 -- Adverse effects of creatine supplementation: fact or fiction? -- Poortmans JR, Francaux M.

Recent trends in football heatstroke fatalities toward significant increases may, in part, be attributable to or aggravated by the use of dietary supplements. Credible scientific evidence has been found that amphetamine derivatives and the ergonomic aid creatine may contribute to subclinical dehydration and heatstroke in selected individuals. Caution is urged in the education and evaluation of football players who train during the hot summer months.
- Neurosurgery 2002 Aug;51(2):283-6; discussion 286-8 -- The neurosurgeon in sport: awareness of the risks of heatstroke and dietary supplements. -- Bailes JE, Cantu RC, Day AL.

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. 

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, 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.


Study shows that creatine supplementation may result in abnormalities in glucose homeostasis in the absence of changes in insulin secretion.
- Ann Nutr Metab 2003;47(1):11-5 -- Creatine supplementation affects glucose homeostasis but not insulin secretion in humans. -- Rooney KB, Bryson JM, Digney AL, Rae CD, Thompson CH.

Creatine may have dangerous interactions with caffeine, ephedra and other herbs and supplements. Creatine may also interact with some prescription medications. Consult with your physician before using.

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