Herbs & Supplements:
Creatine
Supplement Forms / Alternate Names
•
Creatine Monohydrate
Principal Proposed Uses
•
Performance Enhancement
Other Proposed Uses
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Weight Loss, Improved Ratio of Body Fat to Muscle, High Triglycerides, Congestive Heart Failure, Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig's Disease), Huntington's Disease, McArdle's Disease, Mitochondrial Illnesses, Disuse Atrophy
Creatine is a naturally occurring substance that plays an important role in the production of energy in the body. The body converts it to phosphocreatine, a form of stored energy used by muscles.
In recent years, many athletes have tried supplemental creatine as a performance enhancer. If you're a U.S. baseball fan, you probably know that Mark McGwire, the all-time single-season home run champ, takes creatine (along with many other supplements).
Although the evidence for creatine is not definitive, of all sports supplements, it has the most evidence behind it. Numerous small double-blind studies suggest that it can increase athletic performance in sports that involve intense but short bursts of activity.
The theory behind its use is that supplemental creatine can build up a reserve of phosphocreatine in the muscles, to help them perform on demand. Supplemental creatine may also help the body make new phosphocreatine faster when it has been used up by intense activity.
Sources
Although some creatine exists in the daily diet, it is not an essential nutrient because your body can make it from the amino acids L-arginine, glycine, and L-methionine. Provided you eat enough protein (the source of these amino acids), your body will make all the creatine you need for good health.
Meat (including chicken and fish) is the most important dietary source of creatine and its amino acid building blocks. For this reason, vegetarian athletes may potentially benefit most from creatine supplementation.
Therapeutic Dosages
For bodybuilding and exercise enhancement, a typical dosage schedule starts with a "loading dose" of 15 to 30 g daily (divided into 2 or 3 separate doses) for 3 to 4 days, followed by 2 to 5 g daily. Some authorities recommend skipping the loading dose. (By comparison, we typically get only about 1 g of creatine in the daily diet.)
Creatine's ability to enter muscle cells can be increased by combining it with glucose, fructose, or other simple carbohydrates;1,2 in addition, prior use of creatine might enhance the sports benefits of carbo-loading.3
Caffeine may block the effects of creatine.4
Therapeutic Uses
Creatine is one of the bestselling and best-documented supplements for enhancing athletic performance, but the scientific evidence that it works is far from complete. The best evidence we have points to benefits in forms of exercise that require repeated short-term bursts of high-intensity exercise, such as soccer and basketball.5–10 It might also be helpful for resistance exercise (weight training).34,35,55
Creatine has also been proposed as an aid to promote weight loss and to reduce the proportion of fat to muscle in the body, but there is little evidence that it is effective for this purpose.11 Better evidence exists for chromium in this regard.
Preliminary evidence suggests that creatine supplements may be able to reduce levels of triglycerides in the blood.12 (Triglycerides are fats related to cholesterol that also increase risk of heart disease when elevated in the body.)
Creatine supplements might also help counter the loss of muscle strength that occurs when a limb is immobilized, such as following injury.24,54
Finally, preliminary studies, including small double-blind trials, suggest that creatine may be helpful for various muscle illnesses, including amyotrophic lateral sclerosis (Lou Gehrig's disease), congestive heart failure, Huntington's disease, McArdle's disease, mitochondrial illnesses, and muscular dystrophy.13–23,56 Although the evidence is still not strong, creatine seems to be able to reduce fatigue and increase strength in these conditions.
What Is the Scientific Evidence for Creatine?
Exercise Performance
Several small double-blind studies suggest that creatine can improve performance in exercises that involve repeated short bursts of high-intensity activity.25
For example, a double-blind study investigated creatine and swimming performance in 18 men and 14 women.26 Men taking the supplement had significant increases in speed when doing 6 bouts of 50-meter swims started at 3-minute intervals, as compared with men taking placebo. However, their speed did not improve when swimming 10 sets of 25-yard lengths started at 1-minute intervals. It may be that the shorter rest time between laps was not enough for the swimmers' bodies to resynthesize phosphocreatine.
Interestingly, none of the women enrolled in the study showed any improvement with the creatine supplement. The authors of this study noted that women normally have more creatine in their muscle tissue than men do, so perhaps creatine supplementation (at least at this level) is not of benefit to women, as it appears to be for men. Further research is needed to fully understand this gender difference in response to creatine.
In another double-blind study, 16 physical education students exercised 10 times for 6 seconds on a stationary cycle, alternating with a 30-second rest period.27 The results showed that individuals who took 20 g of creatine for 6 days were better able to maintain cycle speed. Similar results were seen in many other studies of repeated high-intensity exercise, although there have been negative results as well.28–33
Isometric exercise capacity (pushing against a fixed resistance) also may improve with creatine.34,35,55 In addition, two double-blind placebo-controlled studies, each lasting 28 days, provide some evidence that creatine and creatine plus HMB (beta hydroxymethyl butyrate) can increase lean muscle and bone mass.36 The first enrolled 52 college football players during off-season training, and the other followed 40 athletes engaged in weight training.
However, studies of endurance or nonrepeated exercise have not shown benefits.37–40 Therefore, creatine probably won't help you for marathon running or single sprints.
High Triglycerides
A 56-day double-blind placebo-controlled study of 34 men and women found that creatine supplementation can reduce levels of triglycerides in the blood by about 25%.41 Effects on other blood lipids such as total cholesterol were insignificant.
Congestive Heart Failure
Easy fatigability is one unpleasant symptom of congestive heart failure. Creatine supplementation has been tried as a treatment for this symptom, with some positive results.
A double-blind study examined 17 men with congestive heart failure who were given 20 g of creatine daily for 10 days.42 Exercise capacity and muscle strength increased in the creatine-treated group. Similarly, muscle endurance improved in a double-blind placebo-controlled crossover study of 20 men with chronic heart failure.43 Treatment with 20 g of creatine for 5 days increased the amount of exercise they could complete before they reached exhaustion.
These results are promising, but further study is needed.44
Safety Issues
Creatine appears to be safe, at least in healthy athletes, although large, systematic, long-term safety studies have not been performed.45 No significant side effects have been found with the regimen of several days of a high dosage (15 to 30 g daily) followed by 6 weeks of a lower dosage (2 to 3 g daily). A placebo-controlled study of 100 football players found no adverse consequences during 10 months to 5 years of creatine supplementation.46 Creatine does not appear to adversely affect the body's ability to exercise under hot conditions.47
However, there are some potential concerns with creatine. Because it is metabolized by the kidneys, fears have been expressed that creatine supplements could cause kidney injury, and there are two worrisome case reports.48,49 However, evidence suggests that creatine is safe for people whose kidneys are healthy to begin with, and who don't take excessive doses.50,51 Nonetheless, individuals with kidney disease, especially those on dialysis, should avoid creatine.
Another concern revolves around the fact that creatine is metabolized in the body to the toxic substance formaldehyde.52 However, it is not clear whether the amount of formaldehyde produced in this way will cause any harm. Three deaths have been reported in individuals taking creatine, but other causes were most likely responsible.53
As with all supplements taken in very high doses, it is important to purchase a high-quality form of creatine, as contaminants present even in very low concentrations could conceivably build up and cause problems.
View References
Last reviewed March 2002 by Medical Review Board
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