Creatine is one of the best-selling 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.)

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 Although the evidence is still not strong, creatine seems to be able to reduce fatigue and increase strength in these conditions. Creatine supplements might also help counter the loss of muscle strength that occurs when a limb is immobilized, such as following injury.24,54

What is the Scientific Evidence for Creatine?

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 20g 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 non-repeated exercise have not shown benefits.37-40 Therefore, creatine probably won't help you for marathon running or single sprints.