Creatine

Creatine is a popular, legal, over-the-counter dietary supplement that athletes use in preparation for sports and during training. It is not a steroid or stimulant but has been known since the early 1900s to have ergogenic properties. It became widely available and popular in 1993. Creatine is typically used to gain weight and muscle mass and to enhance strength training. It [Page 334]appears to be helpful by improving performance in short bursts of intense exercise, such as bench press or sprint cycling. It has no benefit on endurance in aerobic exercise. There is speculation suggesting that creatine supplementation may even help in improving mental performance, but this is still under debate.

The exact mechanism by which creatine supplementation improves athletic performance is not exactly clear, although there are several theories. Creatine seems to help athletes recover from vigorous exercise. The body uses creatine to make phosphocreatine, which acts as a buffer to keep up the production of ATP (adenosine triphosphate). ATP is the fuel used by the muscle during exercise, and the by-product is ADP (adenosine diphosphate). Creatine, among other things, essentially helps regenerate ADP back to ATP, thus replenishing the muscle's energy stores. There can also be weight gain and increased muscle mass with creatine use, up to 2.5 pounds (lb)/week (1.13 kilograms [kg]/ week). Some proportion of this is likely due to water retention.

Creatine, in the monohydrate form or ethyl ester (CEE), is available as a sports drink powder or in a capsule form. The average daily intake of creatine from nutritional sources is about 1 gram (g)/day. It is found naturally in meat and fish. Creatine content in beef is approximately 4.5 g/kg. Tuna has about 4 g/kg, and herring has about 6 to 9 g/kg.

There are no universally agreed-on dosing or duration schedules, but there are some general recommendations. Most agree that the previously suggested “loading doses” of 20 to 30 g/day of creatine supplementation over a period of a week are not needed. They seem to increase potential side effects without giving significant benefits. In general, a maintenance dose of 3 to 5 g/day (or 0.03 g of creatine/kg of body weight), with no loading dose, is suggested. Many athletes cycle creatine use, using it for 3 months at a time followed by 1 month without creatine use. The optimal time to take creatine is immediately after a workout, combined with a drink with a high glycemic index (e.g., a commercial sports drink).

Short-term use of creatine is considered safe but can still have potential side effects. The most common side effects are bloating, diarrhea, and possibly muscle cramping. These effects can be minimized by forgoing the loading dose and staying well hydrated. Creatine does not seem to adversely affect kidney function but is not recommended for athletes with preexisting kidney disease. Because there is a lack of research in the pediatric population, creatine is not recommended by the American College of Sports Medicine (ACSM) for athletes under 18 years.