Muscle Candy

By Christine Gorman

What does it take to be a major league baseball player? Great hand-eye coordination, lots of power and a bottle of androstenedione or creatine. At least that's what the manufacturers of these dietary supplements would like you to believe. Just look at Mark McGwire, who took both substances last year and cranked out a record 70 home runs. And Sammy Sosa, who took creatine and came in second in the great slugfest of 1998. They must know something the rest of us don't.

Then again, maybe not. In separate reports last week, scientists cast doubt on the ability of either substance to perform as advertised. As if that were not bad enough, they also found evidence that using androstenedione might actually make men's breasts bigger and increase their risk of heart disease. Though the studies are not conclusive, they remind us how little is known about many of the most popular dietary supplements.

Androstenedione and creatine often get lumped together in press accounts (like this one) but are two very different compounds. Androstenedione (andro, for short) is an honest-to-goodness steroid and a precursor to testosterone. It is banned by the National Football League and the International Olympic Committee but not by Major League Baseball. Athletes take the supplement in the hope that their body will convert it into testosterone and help them develop bigger muscles during training.

Dream on. In a double-blind placebo-controlled trial of 20 men, published in last week's Journal of the American Medical Association, researchers from Iowa State University found that taking andro did nothing for testosterone levels. Instead, it boosted the amount of estrogen-like compounds in the blood and decreased levels of HDL, or "good" cholesterol, by 12%. Moreover, andro did not help test subjects build muscle mass at all. Scientists want to do more research to be sure, but right now it looks as though all that androstenedione consumed by would-be sluggers after McGwire broke the home-run record may have been taken in vain.

Creatine, on the other hand, is not a steroid and more closely resembles a protein. Synthesized from amino acids, it functions as an energy reservoir for short, high-intensity workouts. You could boost your creatine levels by eating red meat and fish, but it would take an awful lot of steak and sushi.

Most studies of creatine show that it can improve performance by 2% or 3% in repetitive exercises that require short bouts of explosive energy, according to a panel of experts convened by the American College of Sports Medicine for its annual meeting last week. "But those are laboratory results that don't always translate well to the field," warns Ronald Terjung, a physiology professor at the University of Missouri who was chairman of the group. "The expectations athletes have for it are far greater than what is realized."

So far, the data suggest creatine is safe enough. There is some controversy over whether it causes diarrhea, cramping or dehydration. And there have been no long-term studies to show what happens over five, 10 or 15 years. If you still want to be a guinea pig, hook up with a knowledgeable trainer who can monitor your condition. But remember: the only sure way to improve your batting is to get out there and knock the ball around.

For more on dietary supplements, visit our website at time.com/personal You can e-mail Christine at gorman@time.com