From the Guidelines
Creatine is a naturally occurring compound found in muscle cells, primarily in the form of phosphocreatine, which plays a crucial role in energy production during high-intensity exercise. It is both synthesized by the body (in the liver, kidneys, and pancreas) from amino acids and obtained through diet, particularly from meat and fish 1. The metabolism of creatine involves its conversion to phosphocreatine in muscle tissue, which then helps in the regeneration of adenosine triphosphate (ATP), the primary energy carrier in cells.
Uses of Creatine
- Athletic performance enhancement: Creatine is used as a dietary supplement by athletes and fitness enthusiasts to enhance performance during short bursts of intense activity, increase muscle mass, and improve strength and power output 1.
- Muscle mass increase: It helps in increasing muscle mass by promoting protein synthesis and reducing muscle breakdown.
- Neuroprotective effects: Some studies suggest that creatine may have neuroprotective effects, although more research is needed to confirm this.
Metabolism of Creatine
- Absorption: Once ingested, creatine is absorbed into the bloodstream.
- Conversion to phosphocreatine: It is then taken up by muscle tissue and converted to phosphocreatine.
- Excretion: Excess creatine is metabolized to creatinine and excreted through urine 1.
- Creatinine index: The creatinine index, which is a measure of creatinine production, can be used to estimate dietary skeletal muscle protein or mass and edema-free lean body mass 1.
Important Considerations
- Dietary sources: Dietary intake of creatine and creatinine from skeletal (and cardiac) muscle is associated with increased urinary excretion of creatinine 1.
- Individual variability: Factors other than muscle mass can affect the fat-free, edema-free body mass calculation by creatinine kinetics, including errors in the collection or measurement of creatinine in urine or dialysate and large variations in the dietary intake of creatine plus creatinine (meat) 1.
- Side effects: Most healthy individuals tolerate creatine well, with potential side effects including water retention, digestive discomfort, and muscle cramps, though these are generally mild and uncommon.
From the Research
What is Creatine
- Creatine is a popular and widely used ergogenic dietary supplement among athletes, which has been consistently shown to increase lean muscle mass and exercise capacity when used with short-duration, high-intensity exercise 2.
- It is one of the most studied and popular ergogenic aids for athletes and recreational weightlifters seeking to improve sport and exercise performance, augment exercise training adaptations, and mitigate recovery time 3.
Uses of Creatine
- Creatine supplementation produces a variety of beneficial effects in older and patient populations, including improved muscle mass, performance, and recovery 4.
- It may provide additional benefits including enhanced postexercise recovery, injury prevention, rehabilitation, as well as a number of potential neurologic benefits that may be relevant to sports 2.
- Creatine supplementation has been used as a nutritional strategy to help individuals recover from injury and/or manage chronic disease, and it has several health and therapeutic benefits throughout the lifespan 5.
Metabolism of Creatine
- Supplementation consistently demonstrates the ability to enlarge the pool of intracellular creatine, leading to an amplification of the cell's ability to resynthesize adenosine triphosphate 3.
- Creatine plays a critical role in cellular metabolism, particularly during metabolically stressed states, and limitations in the ability to transport and/or store creatine can impair metabolism 5.
- Increasing availability of creatine in tissue may enhance cellular metabolism and thereby lessen the severity of injury and/or disease conditions, particularly when oxygen availability is compromised 5.
Safety and Tolerance
- Creatine supplementation is relatively well tolerated, especially at recommended dosages (i.e. 3-5 g/day or 0.1 g/kg of body mass/day) 4.
- Short- and long-term creatine supplementations have no known significant effects on different studied indexes of kidney function, at least in healthy athletes and bodybuilders with no underlying kidney diseases 6.
- However, it seems more advisable to suggest that creatine supplementation not to be used by sportsmen or women with pre-existing kidney disease or those with a potential risk for kidney dysfunction 6.