They found that electrical stimulation of the neurons caused production of the energy molecule ATP, and this ATP increases myelination.
What is it?
Creatine (creatine monohydrate) is a colorless, crystalline substance used in muscle tissue for the production of phosphocreatine, an important factor in the formation of adenosine triphosphate (ATP), the source of energy for muscle contraction and many other functions in the body.(1, 2)
Creatine monohydrate supplementation increases phosphocreatine levels in muscle in most people, especially when accompanied by exercise or carbohydrate intake.(3, 4) However, about 30% of people who take creatine supplements fail to retain significant quantities in the muscle,(5, 6) which may explain the inconsistent results reported in studies of the effects of creatine on athletic performance.
Creatine may increase exercise-related gains in lean body mass,(7, 8, 9) though how much of these gains represents more muscle and how much is simply water retention is unclear.(10) Most, though not all, controlled studies have shown that 20 grams per day of creatine monohydrate taken for five to six days by sedentary or moderately active people, improves performance and delays muscle fatigue during short-duration, high-intensity exercise such as sprinting or weight lifting.(11, 12, 13) However, elderly people appear to gain only minimal, if any, exercise performance benefits from creatine supplementation,(14, 15) and performance outcomes for trained athletes using creatine supplements in competitive situations have not been consistent.(16, 17, 18) Creatine supplementation does not appear to increase endurance performance and may impair it by contributing to weight gain.(19)
Very little research has been done to investigate the exercise performance effects of long-term (over one month) creatine supplementation. Two controlled long-term trials using untrained women(20) or trained men(21) found that creatine improved gains made in strength and lean body mass from weight-training programs. However, a third preliminary trial found only insignificant gains from creatine supplementation in weight-training football players.(22)
The amount of creatine within cells may be deficient in people with muscular dystrophy. This deficiency may contribute to the weakness and degeneration of muscle tissue seen in this condition. A case report described a 9-year old boy with muscular dystrophy who experienced improved muscle performance after creatine supplementation.(23) A double-blind trial found that creatine supplementation (10 grams per day for adults, 5 grams per day for children) slightly but significantly improved muscle strength and performance of daily activities in people with varying types of muscular dystrophy.(24) Creatine supplementation has also been reported to improve strength in certain rare diseases of muscle and energy metabolism.(25, 26, 27)
For people with congestive heart failure, intravenous creatine has been found to improve heart function, but oral supplementation has not been effective, though skeletal muscle function does improve.(28, 29)
A double-blind, study found that 20 grams per day of creatine taken for five days followed by 10 grams per day for 51 days significantly lowered serum total cholesterol and triglycerides, but did not change either LDL or HDL cholesterol, in both men and women.(30) However, another double-blind trial found no change in any of these blood levels in trained athletes using creatine during a 12-week strength training program.(31) Creatine supplementation in this negative trial was lower—only 5 grams per day was taken for the last 11 weeks of the study.
Where is it found?
Creatine is produced naturally in the human liver, pancreas, and kidneys. It is concentrated primarily in muscle tissues, including the heart. Animal proteins, including fish, are the main source of the 1–2 grams per day of dietary creatine most people consume. Supplements in the form of creatine monohydrate are well absorbed and tolerated by the stomach.
Creatine monohydrate has been used in connection with the following conditions (refer to the individual health concern for complete information):
*** - Athletic performance (for high-intensity, short duration exercise or sports with alternating low- and high-intensity efforts)
** - Athletic performance (for non-weight bearing endurance exercise)
* - Congestive heart failure, High cholesterol, High triglycerides, Muscular dystrophy
*** Reliable and relatively consistent scientific data showing a substantial health benefit.
** Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
* For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.
Who is likely to be deficient?
People involved in intense physical activity, especially those limiting their intake of red meat, may have low muscle stores of creatine. Several muscle diseases, as well as rheumatoid arthritis, and chronic circulatory and respiratory diseases, are associated with lowered creatine levels.(32)
How much is usually taken?
Two methods are used for supplementing with creatine. In the loading method, 20 grams of creatine per day (in four divided amounts mixed well in warm liquid) are taken for five to six days.(33) Muscle creatine levels increase rapidly, which is beneficial if a short-term rise in force is needed, such as during a weight-lifting competition, football game, or sprinting. To maintain muscle creatine levels after this loading period, 2–10 grams per day may be effective.(34, 35)
In another method, 3 grams of creatine monohydrate per day are taken over an extended training period of at least four weeks, during which muscle creatine levels rise more slowly, eventually reaching levels similar to those achieved with the loading method.(36) However, no trials testing exercise performance changes have been done using this method. Taking creatine with sugar appears to maximize muscle uptake.(37, 38)
Caffeine intake should not be excessive, as large amounts may counteract the benefits of creatine supplementation.(39)
Are there any side effects or interactions?
Little is known about long-term side effects of creatine, but no consistent toxicity has been reported in studies of creatine supplementation. In a study of side effects of creatine, diarrhea was the most commonly reported adverse effect of creatine supplementation, followed by muscle cramping.(40) Some reports showed that kidney, liver, and blood functions were not affected by short-term higher amounts (41, 42) or long-term lower amounts (43, 44) of creatine supplementation in healthy young adults. In a small study of people taking 5–30 grams per day, no change in kidney function appeared after up to five years of supplementation.(45) However, interstitial nephritis, a serious kidney condition, developed in an otherwise healthy young man, supplementing with 20 grams of creatine per day.(46) Improvement in kidney function followed avoidance of creatine. Details of this case strongly suggest that creatine supplementation triggered this case of kidney disease. Creatine supplementation may also be dangerous for people with existing kidney disease. In one report, a patient with nephrotic syndrome (a kidney disorder) developed glomerulosclerosis (another serious kidney condition) while taking creatine. when the creatine was discontinued, the glomerulosclerosis resolved.(47)
Muscle cramping after creatine supplementation has been anecdotally reported in three studies.(48, 49, 50)
At the time of writing, there were no well-known drug interactions with creatine monohydrate.
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3. Harris RC, Soderlund K, Hultman E. Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clin Sci 1992;83:367-74.
4. Green AL, Simpson EJ, Littlewood JJ, et al. Carbohydrate ingestion augments creatine retention during creatine feeding in humans. Acta Physiol Scand 1996;158:195-202.
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7. Stone MH, Sanborn K, Smith LL, et al. Effects of in-season (5-weeks) creatine and pyruvate supplementation on anaerobic performance and body composition in American football players. Int J Sport Nutr 1999;9:146-65.
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9. Stout JR, Eckerson J, Noonan D, et al. The effects of a supplement designed to augment creatine uptake on exercise performance and fat-free mass in football players. Med Sci Sports Exerc 1997;29:S251.
10. Kreider RB, Ferreira M, Wilson M, et al. Effects of creatine supplementation on body composition, strength, and sprint performance. Med Sci Sports Exerc 1998;30:73-82.
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28. Andrews R, Greenhaff P, Curtis S, et al. The effect of dietary creatine supplementation on skeletal muscle metabolism in congestive heart failure. Eur Heart J 1998;19:617-22.
29. Gordon A, Hultman E, Kaijser L, et al. Creatine supplementation in chronic heart failure increases skeletal muscle creatine phosphate and muscle performance. Cardiovasc Res 1995;30:413-8.
30. Earnest CP, Almada AL, Mitchell TL. High-performance capillary electrophoresis-pure creatine monohydrate reduces blood lipids in men and women. Clin Sci 1996;91:113-8.
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33. Greenhaff PL. The nutritional biochemistry of creatine. J Nutr Biochem 1997;8:610–8.
34. Vandenberghe K, Goris M, Van Hecke P, et al. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol 1997;83:2055–63.
35. Becque MD, Lochmann JD, Melrose DR. Effects of oral creatine supplementation on muscular strength and body composition. Med Sci Sports Exerc 2000;32:654–8.
36. Hultman E, Soderlund K, Timmons J, et al. Muscle creatine loading in man. J Appl Physiol 1996;81:232–7.
37. Green AL, Hultman E, Macdonald IA, et al. Carbohydrate ingestion augments skeletal muscle creatine accumulation during creatine supplementation in man. Am J Physiol 1996;271:E821–6.
38. Feldman EB. Creatine: a dietary supplement and ergogenic aid. Nutr Rev 1999;57:45–50.
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41. Sewell DA, Robinson TM, Casey A, et al. The effect of acute dietary creatine supplementation upon indices of renal, hepatic and haematological function in human subjects. Proc Nutr Soc 1998;57:17A.
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45. Poortmans JR, Francaux M. Long-term oral creatine supplementation does not impair renal function in healthy athletes. Med Sci Sports Exerc 1999;31:1108–10.
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48. Hultman E, Soderlund K, Timmons J, et al. Muscle creatine loading in man. J Appl Physiol 1996;81:232–7.
49. Vandenberghe K, Goris M, Van Hecke P, et al. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol 1997;83:2055–63.
50. Juhn MS, Tarnopolsky M. Potential side effects of oral creatine supplementation: a critical review. Clin J Sport Med 1998;8:298–304 [published erratum appears in Clin J Sport Med 1999;9:62].
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