Creatine Comes Clean

A decade of research reveals that creatine is the real deal—but watch your step when tempted by other supplements making big promises

Which "wonder supplements" are safe? (John Clark)

IN 1992, when the journal Clinical Science first championed the muscle-building properties of creatine, critics cried foul, warning of side effects including kidney and liver damage. A mountain of research ensued. The result, ten years later, is a rare thumbs-up for the multi-billion-dollar supplement industry: an over-the-counter muscle enhancer backed by research and endorsed—though with decided reluctance—by the medical establishment. Study after study shows that creatine supplements can help you with anaerobic bursts of strength, without the side effects once feared.

As an amino acid manufactured by your liver and kidneys and found in meat, creatine is used to produce adenosine triphosphate (ATP), the molecule that drives muscle contraction. But during intense anaerobic exercise—flashing a 5.10, ripping a double black—creatine stores in your muscles are exhausted, leaving you fatigued and unable to go on. By taking a creatine supplement, research shows you can provide your muscles with more fuel to endure longer bouts of explosive action. In one study at Appalachian State University, 36 track athletes consumed creatine while training and saw gains in their jumping ability and lean-muscle mass.

So do you need creatine? No. But if you're an adult (the jury's still out on whether creatine is safe for adolescents) involved in climbing, mountain biking, or other anaerobic sports, the supplement can provide a performance boost. Those interested, says University of Connecticut physiologist William J. Kraemer, a former member of the U.S. Olympic Sport Science and Technology Committee, don't need to take more than five grams per day (after an initial loading period of 25 grams per day for four days), but do need to put in the extra work—not just down the pills. "Obviously," he says, "you'll get a lot more from it if you include it as part of your strength and resistance training."

Curious to try some of the other "wonder supplements"? Here's what you should know:

What is it? A synthetic hormone used in the production of testosterone. The lowdown: Though andro has a rep as a "legal steroid," studies have revealed no strength-enhancing properties—and a host of dismal side effects, including hair loss and kidney damage. Professional opinion: "You may be the one that this drug does nothing harmful to," says Catherine Jackson, chair of the Department of Kinesiology at California State University at Fresno, "but you'll find better odds in Vegas." Survey says: Be afraid, be very afraid.

What is it? A chemical stimulant derived from the herb ephedra. The lowdown: Ephedrine is ten times stronger than caffeine and is often marketed as an energy booster for the weight room. However, ephedrine can cause increased heart rate and high blood pressure, and it's associated with heart attacks. The stimulant was implicated in the death of Minnesota Viking Korey Stringer last summer. Professional opinion: Says Jackson: "You're playing Russian roulette. I would not let anybody I care about take it." Survey says: Did we mention heart attacks?

What is it? An amino acid produced naturally and synthetically. The lowdown: Like creatine, glutamine is used by muscles in the production of ATP. But few studies have looked at the effects of over-the-counter glutamine supplements on strength training in healthy athletes. Professional opinion: "It's been shown to limit muscle atrophy in people who are ill," says Jackson, "and you can elicit a similar stress response from intense exercise. So glutamine could have a positive effect." Survey says: Wait for new research to emerge.

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