Creatine is a naturally occurring nitrogenous compound produced in the human liver, pancreas and kidneys at a rate of 1-2 g daily. It is synthesised from the amino acids glycine, arginine and methionine and stored primarily in skeletal muscle, where it is in dynamic equilibrium with phosphocreatine and is a precursor to adenosine triphosphate (ATP), the main source of energy for muscle activity and many other biological functions. Orally ingested creatine is absorbed from the small intestine, then distributed via creatine transporters around the body to muscles and nerves (Persky et al 2003). These transporters also serve as a clearance mechanism because of creatine 'trapping' by skeletal muscle. It is ultimately converted to creatinine and excreted by the kidneys.
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