Creatine is a naturally occurring amino acid the human body makes in the liver, kidneys and pancreas. You can also obtain dietary creatine through meat, fish and nutritional supplements. The primary function of creatine is to supply energy to muscles during intense, short-duration physical activity. Creatine serves important functions in muscle tissue, but not all the effects of creatine supplementation are well-understood. Consult your physician before taking nutritional supplements.
Function of Creatine in the Body
In the body, creatine is converted into creatine phosphate or phosphocreatine, which is stored in skeletal muscle. During short bursts of high-intensity exercise such as sprinting or weightlifting, phosphocreatine is converted into a substance called adenosine triphosphate, or ATP, that supplies energy to working muscle fibers -- particularly, fast-twitch glycolytic fibers. According to the University of California San Diego's Muscle Physiology Laboratory, your body synthesizes about 2 g of creatine daily. Creatine levels in the body may be augmented with dietary creatine, but only to a certain extent, according to UCSD.
Effects of Supplementation on Athletic Performance
Supplements may improve certain aspects of athletic performance for some people. According to MedlinePlus, clinical research indicates creatine supplements are possibly effective for improving athletic performance among young, healthy people during brief, high-intensity physical activities. Specifically, creatine may benefit performance by improving strength and lean muscle mass, according to the University of Maryland Medical Center. However, creatine does not appear to enhance aerobic exercise or to provide any athletic benefits for older people or highly trained athletes, MedlinePlus says. Creatine supplementation also won't provide athletic benefits if you already have sufficient creatine stores, UMM notes. As of January 2011, creatine studies have been conducted on too small of a scale to draw firm conclusions from, according to MedlinePlus.
Effects in Disease Treatment
Creatine may also produce beneficial effects in the treatment of certain health conditions. According to UMM, preliminary clinical studies suggest that creatine's muscle-conditioning effects may help treat muscle weakness associated with muscular dystrophy and heart failure. Creatine may also help slow the progression of early-stage Parkinson's disease, according to MedlinePlus. Other conditions that MedlinePlus rates creatine as being "possibly effective" for include gyrate atrophy and McArdle's disease. As with creatine's effects on athletic performance, there isn't yet conclusive evidence indicating creatine's effectiveness in disease treatment.
Side Effects and Precautions
Creatine supplementation is associated with certain side effects ranging from mild to serious. According to MedlinePlus, creatine causes muscles to draw water from the rest of the body, so it is important to drink plenty of water and to avoid exercising in the heat to prevent dehydration when taking creatine. Creatine is also associated with weight gain from water retention. At recommended doses, creatine is likely safe, though it may cause gastrointestinal side effects such as stomach pain, nausea and diarrhea. At high doses, creatine is considered "possibly unsafe," according to MedlinePlus, due to concerns that it could harm the liver, kidney or heart. Pregnant or nursing women and people with kidney or liver disease, high blood pressure or diabetes should avoid creatine.
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