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 insulinlike 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 activates anabolic signaling factors in muscle. Although creatine does promote a degree of water retention (up to 6 to 9 pounds after a creatine load regime), it also promotes actual muscular growth through the anabolic mechanisms described above.
But according to a recently published study, creatine may also aid muscular gains through its activity in curtailing some of the effects of cortisol. Cortisol is a hormone produced in the adrenal gland cortex that is associated with stress. As such, it’s often referred to as a “stress hormone,” along with the catecholamine hormones, epinephrine and norepinephrine. Cortisol shares a bad reputation among bodybuilders along with estrogen, although both hormones have both a good and bad side. Estrogen, for example, can promote gynecomastia or male breast formation if produced in excessive amounts. It may also promote subcutaneous fat deposition, or increased fat stores just under the skin. But few bodybuilders realize that estrogen is also involved in muscle repair following exercise, boosts nitric oxide levels, and helps lower abdominal fat stores. It is also essential for brain and heart function, and recent studies show that activation of a particular estrogen receptor in muscle promotes the activity of muscle satellite cells. Activating another estrogen receptor (there are two) helps prevent prostate cancer,although activation of the other (estrogen receptor-A) promotes prostate cancer. So you wouldn’t want to eliminate all estrogenic activity in men, although that’s what many bodybuilders do when they chronically use estrogen-blockers, such as Tamoxifen citrate (Nolvadex) or aromatase-inhibiting drugs, which prevent the synthesis of estrogen from androgens, such as testosterone.