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Creatine

Creatine

Description

With its promises of bigger muscles and improved athletic performance, creatine has generated more interest and controversy than almost any other dietary supplement. It is widely used by body builders and athletes of all levels, from famous baseball sluggers to high school jocks. Even without taking supplements, all people have a small amount of this protein in their bodies. Some of it comes from food, especially meat and fish, while the rest is made by the body from amino acids . No one disputes the fact that creatine plays an important role in converting food into energy. The real question is whether taking extra amounts of creatine can make muscles bigger, boost athletic performance, or improve the health of people with muscle or nerve disease.

Creatine is considered important because it can increase the amount of energy available to working muscles. The protein is used by the body to make a chemical compound called adenosine triphosphate (ATP), the immediate fuel source used by muscles during short but intense bursts of activity. Through its conversion into phosphocreatine, a related substance, creatine appears to delay muscle fatigue by re-supplying muscles with ATP. Because creatine can be stored for later use by cells, consuming extra amounts of the protein may create a deeper energy reserve for muscles and other tissues. Excess creatine is eliminated by the kidneys. This means that creatine supplements may be of little value in people who have sufficient levels of the protein, since the kidneys automatically remove extra amounts.

A significant amount of research is still required to determine the long-term effects of taking creatine, proper dosage, and whether age, gender, or the presence of existing diseases can affect use of the supplements. However, as of 2002, studies found a lower risk of training-related injuries in athletes who used the supplement and new therapeutic uses of the supplement were being tested.

General use

Creatine supplements are generally used by weight lifters and athletes who wish to optimize their workouts or enhance athletic performance. It is important to distinguish fact from myth regarding the possible benefits of creatine. The scientific evidence suggests that creatine may not have much usefulness as a muscle-enhancing agent, though it does appear to moderately improve performance in exercises or sports that require short, repeated bursts of high-energy activity. For example, creatine may provide a slight energy boost to the muscles of a weight lifter during extended repetitions or a basketball player who makes yet another drive to the hoop. However, creatine does not appear to increase aerobic capacity or improve performance in endurance-type activities such as marathon running. Apart from its uses in body building and athletics, creatine may prove beneficial in the treatment of certain diseases involving the muscles or nerves.

In one study of 16 physical education students, for example, those who received 20 g a day of creatine for about a week were more capable of maintaining speed during a cycling exercise . The students peddled on a stationary bike for six seconds at a stretch, repeating the exercise 10 times and taking 30-second breaks between attempts. A study of 14 active men, published in the Journal of the American Dietetic Association in 1997, investigated creatine supplementation and repetitive, high-intensity resistance exercises involving the bench press and jump squats. The authors reported that taking 25 mg a day of creatine for one week enhanced muscular performance during the resistance exercises and also increased body mass. It is not certain if the higher body mass reflected increases in muscle or simply excess water weight, which may give the impression of bigger muscles.

In addition to individual studies, several articles in medical journals have reviewed the scientific literature concerning creatine. According to an article published in the Journal of the American College of Nutrition in 1998, creatine supplements may boost performance during certain physical exercises that require repeated, intense efforts and allow only a short interval of rest between attempts. The author noted that using the protein appears to increase body mass in men (though the initial increase is probably water) and may increase lean body mass when combined with resistance exercises over a long period of time. A meta-analysis published in the International Journal of Sports Medicine in 1997 discussed the possible benefits of creatine supplements and how the protein may produce its effects. The authors suggest that creatine may be able to delay muscle fatigue and quicken recovery during repetitive, high-intensity exercises by helping the body to re-supply muscles with ATP. Once ATP reserves get low due to exertion, the higher levels of creatine and phosphocreatine in muscles facilitate the speedy production of new ATP. The authors conclude that creatine supplements may be useful during repetitive training exercises and could provide a competitive edge in sports that require repeated, explosive bursts of activity such as basketball or soccer.

One of the most thorough and authoritative investigations of creatine supplementation was conducted by a panel affiliated with the American College of Sports Medicine (ACSM). This group, which reviewed over 100 studies involving creatine, published some of their findings in early 2000 in Medicine and Science in Sports and Exercise. The panel found that creatine can boost performance in certain repetition-type exercises that involve brief but powerful exertion. They noted that creatine does not appear to make people stronger or improve aerobic capacity. Creatine can produce weight gain after only a few days, but this is most likely due to water retention. Since most of the creatine research has been conducted in healthy young men, there is limited information about how age or gender may affect use of the protein. The panel pointed out that, while creatine may produce a small but significant boost in performance in very specific exercises, it usually cannot satisfy the overly high expectations of most people who use the supplement.

A 2002 European study reported that creatine supplements could actually speed rehabilitation for injured athletes. Patients who were immobilized in a leg cast for two weeks were given a dietary supplement of creatine before immobilization and then daily throughout the rehabilitation. They showed faster recovery of strength and muscle mass than subjects not receiving creatine.

Aside from sports, research also suggests that creatine may be helpful in the treatment of certain diseases affecting the muscles or nerves, including Huntington's disease, Lou Gehrig's disease (amyotrophic lateral sclerosis), and congestive heart failure. Creatine is not considered a cure for these diseases, but may help to alleviate symptoms (such as muscle weakness and fatigue) or possibly extend survival. In one study involving mice, conducted by researchers from Harvard Medical School and Cornell University Medical College, creatine appeared to provide protection against Lou Gehrig's disease. The protein worked twice as well as Riluzole, a prescription drug approved by the FDA for treatment of the disease.

Preparations

Dosage of creatine usually consists of a loading dose of 1030 g a day (divided into several doses) for four to six days, followed by a maintenance dose of 25 g a day. It is not clear if the high loading dosage is actually necessary. The ACSM panel noted that smaller dosages (3 g a day) achieve the same effects if taken for several weeks.

Even without taking supplements, most people get about 1 g of creatine through their diets . Some authorities believe it is safer for people to avoid creatine supplements altogether in favor of eating foods that contain the protein. The best sources of creatine are meat, poultry, and fish. Getting too much dietary creatine is not considered a significant risk because only small amounts of the protein are contained in food.

Precautions

Creatine supplements are not known to be harmful when taken in recommended dosages, though there are some precautions to consider. People with kidney disease should not use creatine without medical supervision. Due to lack of sufficient medical study, creatine should be used with caution in children under age 16, women who are pregnant or breast-feeding, and people with liver disease.

The long-term health risks associated with taking creatine are unknown. Surprisingly, though, use of the supplement is increasing, even among children and adolescents. Some adults have used the drug on a long-term basis without knowing the effects of long-term use.

Side effects

A slight weight gain due to water retention is probably the most common side effect. Nausea , cramping, dehydration, diarrhea , and increased blood pressure have also been reported.

To avoid possible side effects, do not take creatine immediately before or during exercise.

Drink plenty of fluids (six to eight glasses a day) while using creatine in order to prevent dehydration.

Interactions

Taking creatine with large amounts of carbohydrates may increase its effectiveness. Caffeine may decrease the effects of the supplement.

Resources

BOOKS

Paoletti, Rodolfo. Creatine: From Basic Science to Clinical Application. Boston: Kluwer, 1999.

PERIODICALS

"Creatine Supplementation Speeds Rehabilitation." Health and Medicine Week (January 21, 2002): 6.

Kubetin, Sally Koch. "Demand Swells for Sports Supplements." Family Practice News (February 15, 2002): 1.

Mujika, I., and S. Padilla. "Creatine Supplementation as an Ergogenic Acid for Sports Performance in Highly Trained Athletes: A Critical Review." International Journal of Sports Medicine 18, no. 7 (1997): 491-6.

"Studies Say Creatine is OK." Obesity, Fitness & Wellness Week (January 12, 2002): 12.

Terjung, R. L., P. Clarkson, E. R. Eichner, et al. "The Physiological and Health Effects of Oral Creatine Supplementation [In Process Citation]."Medicine and Science in Sports and Exercise 32, no. 3 (2000): 70617.

Volek, J. S., W. J. Kraemer, J. A. Bush, et al. "Creatine Supple-mentation Enhances Muscular Performance During High-Intensity Resistance Exercise."Journal of American Dietetic Association 97, no. 7 (1997): 76570.

Williams, M. H., and J. D. Branch. "Creatine Supplementation and Exercise Performance: An Update."Journal of the American College of Nutrition 17, no. 3 (1998): 21634.

ORGANIZATIONS

American College of Sports Medicine. 401 W. Michigan St., Indianapolis, IN 46202-3233. cheister@acsm.org. <http://www.acsm.org>.

Grand Forks Human Nutrition Research Center. 2420 2nd Ave N., Grand Forks, ND 58202. <http://www.gfhnrc.ars.usda.gov>.

Greg Annussek

Teresa G. Odle

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creatine

creatine (kree-ă-teen) n. a product of protein metabolism found in muscle. c. kinase (CK, c. phosphokinase, CPK) an enzyme involved in the breakdown of creatine to creatinine, isomers of which originate in the brain and thyroid, skeletal muscle, and heart. Damage to these tissues results in increased levels of the isomer in the serum. c. phosphate (phosphocreatine, phosphagen) the phosphate of creatine, which acts as a store of high-energy phosphate in muscle and serves to maintain adequate amounts of ATP.

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creatine

creatine A compound, synthesized from the amino acids arginine, glycine, and methionine, that occurs in muscle. In the form of creatine phosphate (or phosphocreatine), it is an important reserve of energy for muscle contraction, which is released when creatine phosphate loses its phosphate and is converted to creatinine, which is excreted in the urine (at a rate of 1.2–1.5 g/day in humans). See also phosphagen.

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creatine

creatine A derivative of the amino acids glycine and arginine, important in muscle as a store of phosphate for resynthesis of ATP during muscle contraction and work. Not a dietary essential, since it is synthesized in the body, but widely sold in supplements to improve athletic performance, with limited evidence of efficacy.

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