Creatine, or creatine monohydrate [NH2-C(NH)-NCH2(COOH)-CH3], is a naturally occurring amino acid that helps to supply energy to muscle cells. The word derives from the Greek kreas (meat).

Typically, half of the creatine (Cr) in our body comes from the food we eat (mainly from meat and fish), while the other half is synthesized from certain amino acids (glycine and arginine) in the liver, pancreas and kidneys. 95% is stored in the skeletal muscles, the rest in the brain, heart and testes.

In the muscles, a fraction of the total creatine binds to phosphate. The reaction is catalysed by creatine kinase, and the result is phosphocreatine (PCr). Phosphocreatine binds with adenosine diphosphate to convert it back to ATP (adenosine triphosphate), an important cellular energy source.

There is scientific evidence that taking creatine supplements can marginally increase athletic performance in high-intensity, anaerobic exercise. Ingesting creatine can increase the level of phosphocreatine in the muscles up to 20%. An additional study, published in August 2003 in the Royal Society journal Proceedings B, suggests increased mental capabilities as a result of oral intake of creatine over a 60 day period.

It must be noted creatine has no significant effect on aerobic exercise.

A majority of studies conclude that creatine supplementation increases both total and fat-free body mass. Since body mass gains of about 1 kg can occur in a week's time, several studies suggest that the gain is simply due to greater water retention inside the muscle cells. However, studies into the long-term effect of creatine supplementation suggest that body mass gains cannot be explained by increases in intracellular water alone. In the longer term, the increase in total body water is reported to be proportional to the weight gains, which means that the percentage of total body water is not significantly changed. The magnitude of the weight gains during training over a period of several weeks argue against the water-retention theory.

It is possible that the initial increase in intracellular water increases osmotic pressure, which in turn stimulates protein synthesis. A few studies have reported changes in the nitrogen balance during creatine supplementation, suggesting that creatine increases protein synthesis and/or decreases protein breakdown.

Others suggest that, since creatine may allow athletes to train harder and recover faster, the enhanced training stimulus may promote greater muscle hypertrophy in the long term. Ultimately, the increase in muscle mass is probably attributable to a combination of all these factors: greater water retention inside the muscle cells, increase in protein synthesis and/or decrease in protein breakdown and greater training stimulus.

Creatine can cause dehydration due to increased absorption of water by the skeletal muscles. It is therefore not recommended for people with kidney disease. Current studies indicate that short-term creatine supplementation is safe, but the effects of long-term supplementation are still unknown.

Creatine use is not considered doping and is currently acceptable to all sports-governing bodies.


External links

fr:Cratine ja:クレアチン pl:Kreatyna sv:Kreatin


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