Creatine is a naturally occurring amino acid (protein building block) found mainly in muscles. Fifty percent of creatine in our bodies is ingested through the foods we eat while the other 50% is made in the liver, kidney, and pancreas. Roughly one-third is in its free form as creatine, while the remainder is bound to phosphate and called creatine phosphate or phosphocreatine. During high-intensity, short-duration exercise, such as lifting weights or sprinting, phosphocreatine is broken down into creatine and phosphate. The energy released in this process is used to regenerate ATP, a major source of energy within the human body that drives a number of biological processes including muscle contraction and protein production.

Creatine supplements have gained much popularity in recent years, particularly among body builders and competitive athletes. In fact, as many as 4% of Americans have taken a sports enhancing supplement. Estimates ranging from $45 million to $1.4 billion dollars are spent on sports related supplements each year, including roughly $14 million on creatine specifically. The attraction of creatine, again, is that it may enhance athletic performance, particularly during high-intensity, short-duration sports (like high jumping and weight lifting).

However, not all studies have confirmed this beneficial response and not every individual responds positively to creatine supplements. For example, people who tend to have naturally high stores of creatine in their muscles will not experience an energy-boosting effect from extra creatine. Preliminary studies also suggest that creatine's ability to increase muscle mass and strength could hold special advantages for combating muscle weakness associated with various neuromuscular disorders.

Athletic Performance

Although not all studies agree, some conducted in both animals and people have shown that creatine supplements improve strength and lean muscle mass during high-intensity, short-duration exercises (such as weight lifting). These positive effects were only seen in young people (roughly 20 years of age). Studies in older individuals (60 to 80 years of age) did not find the same effects. Although it does not appear to improve physical endurance, there is some suggestion that speed for short periods of time may improve with use of creatine.

The use of creatine for athletic performance, however, is controversial and its use is restricted by several athletic organizations. The National Collegiate Athletic Association (NCAA), for example, prohibits member schools from giving creatine and other muscle building supplements to their athletes. The French Agency of Medical Security for Food (AFSSA) asserts that the use of creatine supplements is "against the spirit of sportsmanship and fair competition." The Healthy Competition Foundation, a nonprofit organization founded by the Blue Cross and Blue Shield Association to educate the public about the risks of performance-enhancing drugs in athletic competition, "urges abstinence from creatine use and reminds athletes, coaches, and parents that skill, dedication and hard work are the most important qualities for success in sports..."

In addition, there is concern about athletes taking pure creatine supplements because of the potential for serious side effects such as damage to the kidneys in otherwise healthy people and the risk of inhibiting the body's natural formation of creatine. Some suggest that the solution is to only use creatine as part of a complex sport nutritional supplement that includes other exercise enhancing substances but this theory has yet to be tested.

Also of concern is the marketing of creatine containing supplements directly to teens. This age group is particularly vulnerable to the enticing but misleading claims about changing one's body shape with little effort. One survey conducted with college students found that teen athletes frequently exceed the recommended loading and maintenance doses of creatine. Meanwhile, neither safety nor effectiveness in those under 19 has ever been tested.

Neuromuscular Disorders

Neuromuscular disorders is a general term referring to a group of conditions characterized by muscle weakness and wasting. They are caused by either a problem in the muscles themselves or as a consequence of a dysfunction of the nerves responsible for making muscles move. Examples include muscular dystrophy, amyotrophic lateral sclerosis (ALS; often referred to as "Lou Gehrig's disease and characterized by progressive loss of control of voluntary muscles due to destruction of nerve cells in the brain and spinal cord), and McArdle's disease (a disease characterized by abnormal storage of glycogen [a form of energy made from the sugar glucose] in muscle tissue leading to muscle pain, cramps, stiffness and poor exercise tolerance).

Given that some studies suggest that creatine supplements may improve exercise performance in athletes, researchers have asked the question of whether this benefit may be conferred to people with neuromuscular disorders as well. Preliminary research in people and animals suggests that creatine supplementation for short periods of time (generally, 5 to 7 days) may improve muscle strength, increase lean body mass, and enhance exercise performance in those with neuromuscular disorders. Long-term, well-designed trials are needed. In fact, the Muscular Dystrophy Association is currently conducting a large-scale study comparing the effectiveness of creatine to placebo in people with certain forms of muscular dystrophy.

High Cholesterol

A preliminary study suggests that creatine supplements may help lower levels of blood lipids (cholesterol) in men and women with abnormally high concentrations of lipids in their blood.

Congestive Heart Failure (CHF)

In a few studies of people with congestive heart failure, those who took creatine (in addition to standard medical care) had significant improvement in symptoms and exercise capacity compared to those who received placebo.

Other

Some preliminary evidence from animal studies suggests that creatine may prove beneficial after brain injury from trauma (such as after a car accident) by preserving brain function. It is premature to draw conclusions for people from this information. This potential application of creatine requires further research.

Similarly, one study of a small number of people with rheumatoid arthritis examined whether creatine could help combat muscle weakness, a common complication of this joint disorder. Muscle strength did improve in 8 of the 12 participants in the study. However, the authors concluded that the data was not strong enough yet to draw definite conclusions for those with rheumatoid arthritis. More research will be useful.

Fifty percent of creatine in our bodies is made from other amino acids in the liver, kidney and pancreas, while the other 50% is ingested through the foods we eat. Wild game is considered to be the richest source of creatine, but lean red meat and fish (particularly herring, salmon, and tuna) are also good sources.

Supplements are commonly sold in powder form, although liquid preparations, tablets, capsules, energy bars, fruit-flavored chews, drink mixes, and other preparations are also available.

Pediatric

Despite the growing numbers in grades 6 through 12 using creatine, safety and effectiveness have not been tested in those under 19. Therefore, use of creatine supplements is not recommended for children or teens.

Adult

Manufacturers of sports supplements tend to put the following dose on labels of their products: 5 grams of creatine monohydrate four times per day (20 grams total per day) for one week. The muscles will then be "loaded" with creatine and a maintenance dose of 2 to 5 grams per day is adequate to sustain stores of creatine in the muscles. It appears that the absorption of creatine is enhanced when it is taken together with carbohydrate foods (such as fruits, fruit juices and starches).

The doses previously mentioned have been tested frequently in athletes. It is important to note, however, that it is not known whether these dosages have the same effects in non-athletes.

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable healthcare provider.

Side effects of creatine include weight gain, muscle cramps, muscle strains and pulls, stomach upset, diarrhea, dizziness, high blood pressure, liver dysfunction, and kidney damage. The weight gain is thought to be due primarily to water retention. Creatine should not be used by anyone who already has problems kidney function, high blood pressure, or liver disease. Taking creatine supplements may prevent the body from making it's own natural stores. The long-term consequences of this are not known.

A 2001 report by the Food Safety Agency of France (AFSSA) raised questions about creatine supplements possibly putting users at greater risk for cancer, particularly if such supplements are taken for long periods of time. However, the European Commission and the Council for Responsible Nutrition in the United States both determined that AFSSA's claims are unsubstantiated and not based on any scientific evidence of a connection between creatine and cancer. All three organizations do agree, though, that risks of long-term use of creatine are not known at this time.

Creatine supplements containing contaminants from the production process have been reported. Be sure to buy products made by established companies with good reputations, and who distribute their products through trustworthy and knowledgeable establishments.

If you are currently being treated with any of the following medications, you should not use creatine without first talking to your healthcare provider.

Cimetidine, Diuretics, NSAIDs, and Probenecid
Creatine may increase the likelihood of damage to the kidneys if taken with cimetidine (a medication for used for heartburn and to prevent ulcers), diuretics, probenecid (used for gout), or non-steroidal anti-inflammatory (NSAID) medications (such as ibuprofen).

Other substances
The combined use of caffeine, ephedra (a very concerning substance frequently found in sports or weight loss supplements), and creatine has been associated with at least one report of a stroke in a male weight lifter. It is believed that the combination of creatine with herbs and medications that stimulate the central nervous system contributed to the stroke.

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