Creatine is probably the most popular food supplement used by bodybuilders, and for good reason. It works for 80% of those who use it. The 20% for whom creatine isn't effective are usually habitual heavy meat-eaters. Red meat is the richest source of natural creatine, containing an average of two grams of creatine per pound, although about 30% of the creatine content of meat is degraded when the meat is cooked. Still, ingesting meat regularly, at least three times a week, will eventually load the muscles with creatine. Since the amount of creatine that can be stored in muscle is limited, those who consume a lot of red meat may get some additional storage of creatine if they use a supplement, but not much. This is in contrast to vegetarians, who show the lowest body stores of creatine. When they consume creatine, the results in regard to training are often dramatic.
Creatine itself is an amino acid byproduct. It's produced every day in the liver, pancreas, and kidneys by way of an enzymatic cascade that begins with the amino acids, arginine, methionine, and glycine. Muscle tissue is the primary storage site for creatine in the body, containing 95% of creatine stores. About 5% of creatine is also stored in the brain and the testes. The presence of creatine in the brain is significant since research conducted in recent years shows that supplemental creatine can have beneficial effects on several types of brain diseases, especially those involving a neuromuscular component.
The primary function of creatine is to aid muscle energetic reactions. All sources of energy in food eventually are converted into the most elemental source of cellular energy, adenosine triphosphate or ATP. ATP consists of three phosphate groups attached to an adenosine backbone. Energy is produced when one of the phosphate groups breaks off from the ATP structure. This converts ATP into ADP. But creatine, which is stored in muscle as both free or unbonded creatine, and mainly as creatine phosphate, contributes a phosphate group to the degraded ADP, which immediately converts it back to ATP. In this sense, creatine acts like a second battery would in a car, kicking in when the first battery runs out of energy.
The research on creatine is voluminous, with new studies emerging constantly in the medical literature. In relation to muscle function, other studies have shown that creatine also exerts a buffering action in muscle, which further reduces muscular fatigue during high-intensity exercise. Creatine may also offer anabolic effects. For example, some studies show that creatine may promote the activity of muscle satellite cells, which are muscle stem cells vital for muscle repair and hypertrophy (growth). It may do this by promoting the activity of intramuscular insulin-like growth factor-1 (IGF-1), probably the most potent intramuscular anabolic hormone. Creatine also promotes muscle gains by activating a cellular hydration process that in turn . . .