Creatine and creatinine washout in athletes 111 Original article Jean-Marc Schedel 1,2,3 , Masato Tanaka 2 , Hiroaki Tanaka 2 , Akira Kiyonaga 2 , Munehiro Shindo 2 , Philippe Terrier 1 , Yves Schutz 1 1 Institute of Physiology, Faculty of Medicine, University of Lausanne, Lausanne, Switzerland 2 Laboratory of Exercise Physiology, Department of Sport Sciences, Fukuoka University, Fukuoka, Japan 3 Laboratory of Exercise Physiology and Biomechanics, Graduate School of Physical Education, Chukyo University, Toyota-Aichi, Japan Consequences of one-week creatine supplementation on creatine and creatinine levels in athletes’ serum and urine Schweizerische Zeitschrift für «Sportmedizin und Sporttraumatologie» 48 (3), 111–116, 2000 Summary We explored the washout period of creatine (Cr) after repeated ingestions of high doses of exogenous Cr. Ten athletes ingested daily, in a randomized double-blind study design, 30 g of exoge- nous Cr (n = 5, Cr-group) or a placebo (n = 5, Pl-group). Serum and urine samples were collected 1) before supplementation (BEFO- RE), 2) after one week Cr supplementation (AFTER), and 3) one week later without supplementation (LATER). The Cr and crea- tinine (Crn) concentrations in serum (sCr, sCrn) and in multiple spots urine (uCr, uCrn) were measured. We observed a significant rise (p < 0.01) in sCr, uCr and sCrn between BEFORE and AFTER supplementation in Cr-group, as well as a significant difference between Cr-group and Pl-group. Body weight increased signifi- cantly (+1.5 kg), but relative body fat (%fat) was unchanged. After the washout period in LATER Cr-group, sCr and uCr decreased to low residual values. No loss of body weight occurred during this period. In contrast, sCrn and uCrn returned to baseline values. In conclusion, regular uptake of high doses of exogenous Cr affects both Cr and Crn concentrations in serum (sCr: 14 folds; sCrn: 1.2 folds) and urine (uCr: 140 folds; uCrn: 1.5 folds). An abuse of Cr is therefore mostly spilled over in urine. Surprise drug tests, such as doping controls, happening during the period of Cr supplementa- tion can reveal an important increase in Cr and Crn concentrations, although subjects stopped suddenly Cr loading. The discernible effect of Cr supplementation on these values disappeared within one week. Key words: Creatine loading, creatinine, non-enzymatic conversion, wash out, serum, urine, human, doping, sport nutrition Introduction Since the discovery of creatine (Cr) in 1832 by Chevreul, many scientists have studied the metabolism and the function of this molecule largely used by athletes [1, 2]. Many comprehensive studies on Cr supplementation and reviews on this topic have been published [3–9]. Briefly, Cr pool in man is approximately 1.7 g/kg, most of which being located in skeletal muscle. The averaged turnover for an adult male is ~2 g/day . Cr is naturally ingested with food (meat, fish, milk) or is endogenously produced from arginine, glycine and methioni- ne in kidney and liver [1, 3, 9–12]. Muscle fibers can store a high Cr concentration (from approximately 120 to a maximum limit of 160 mmol/kg dry muscle). The enzyme Creatine-kinase (CK) con- verts Cr into phosphorylated form called phosphocreatine (PCr). This easy releasable energy stored in phosphate bond constitutes the basic mechanism supporting many cellular energetic activities such as muscular contraction, cell growth and protein synthesis [7, 13–17]. The end product of Cr and PCr metabolism is a cyclic stable compound called creatinine (Crn) that will be released in blood and then filtered by the kidney and excreted in urine [18–32]. Because no evidence of direct toxicity has been observed fol- lowing chronic or acute Cr supplementation, many studies were performed with relative high doses of exogenous Cr [9]. When chronic Cr supplementation was combined with daily hard exercise, the Cr content in exercised muscles was enhanced. Several authors also reported that the intracellular Cr pool could be substantially increased, in particular when the initial Cr concen- tration is low [5, 6, 9]. Studies using prolonged Cr loading have generally shown an ergogenic effect on anaerobic performances such as high-intensity short-duration exercises, but not for endurance-type aerobic exer- cises [1, 3–5, 9, 32]. In most of these Cr supplementation studies, a moderate increase in body weight was observed, explained by some authors by water retention [1, 9, 17]. Consequently, Cr became a fashion compound for athletes attempting to increase their anaerobic performance or muscular mass. Although no evidence of toxicity was demonstrated, many questions remain open about the changes in body fluid concentra- tions in response to large doses of ingested Cr, and this could be important for doping tracking or for foreseeing the potential side effects of long term Cr intake.