Creatine

Creatine is a combination of amino acids that are stored in the skeletal muscles. These muscles can use one of its derivatives-creatine phosphate-to sustain a muscle contraction when the usual fuel-a substance called ATP (adenosine triphosphate)-has been exhausted. In simplified terms, here's an example of how it works: when you lift a heavy weight, the muscles of your arms contract, or shorten, to provide the needed strength and resistance. The energy for this contraction is derived by converting ATP to ADP (adenosine diphospate). When the muscles' reserves of ATP are exhausted, creatine comes to the rescue by giving over its phosphate molecule to make more ADP. High reserves of creatine phosphate allow the muscles to work longer and harder.

The body makes creatine by combining certain amino acids, the building blocks of protein, and then storing it in the muscles. Creatine supplements are marketed as muscle builders and athletic performance enhancers.

The scientific evidence backing creatine-supplement efficacy is mixed, at best. There is some evidence that creatine supplements may help muscles hold more water, and theoretically, creatine-rich fluid might supply extra fuel in times of need. A few studies have linked creatine supplements with modest increases in muscle mass and strength among athletes; but many have found no apparent effects. Most of the impetus for its use has been based on testimonials by bodybuilders and professional athletes who claim that creatine has given them a competitive edge. These testimonials have prompted millions of young athletes to take creatine supplements, often as a safer alternative to anabolic steroids. Scientists stress, however, that no supplement alone will increase muscle mass and strength; instead, it is increased muscle use that accomplishes these objectives. In other words, it's working out-not creatine-that builds those bulging muscles that weight lifters and other athletes like to display.

The body makes all the creatine that it ordinarily needs from high-protein foods-muscle meat, fish, poultry, egg whites, milk and milk products, soybeans, and combinations of legumes and grains.

Supplements are available in several forms including creatine monohydrate, a crystalline powder. It can be mixed with a full glass of water or simply sprinkled on food. Be sure to drink plenty of water during the course of the day, but avoid coffee, colas, and other caffeinated drinks. Caffeine has a diuretic effect, which may counteract any beneficial effect of creatine by drawing fluids out of the muscle tissue.

Proponents of creatine supplements recommend starting with a relatively high loading dose of 1 teaspoon (5 g) four or five times a day for the first five to seven days, and after that cutting back to 1 teaspoon twice a day every other day, or no more than five days a week. Some experts recommend limiting daily use to three weeks a month, with a full month off after two months of taking the supplements. Some athletic trainers recommend taking creatine as part of the preseason conditioning, and then discontinuing it during the competitive season, although there is no scientific evidence to support such recommendations.

High doses-for example, 5 g a day for more than a few weeks-can cause nausea, dizziness, diarrhea, and possibly muscle cramps. Long-term use of supplements may harm the kidneys. Even in the absence of kidney problems, creatine supplements can result in misleading blood tests. This occurs when tests show elevated blood levels of creatinine, a metabolic by-product of creatine. Ordinarily, elevated creatinine points to a kidney problem. Doctors also caution against teenagers taking creatine supplements because its long-terms effects on the kidneys and liver are unknown.

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