Sports-supplement dangers.

Americans spent an estimated $1.4 billion on sports supplements in 1999, hoping that the pills, drinks, and powders would help them bulk up, slim down, or compete more effectively. But people who take these products are actually conducting what amounts to a vast, uncontrolled clinical experiment on themselves with untested, largely unregulated medications.

The few good scientific studies available on these "dietary" supplements suggest that they either are ineffective or, at best, produce only slight changes in performance. More disturbing, they can contain powerful and potentially harmful substances, such as:

* Androstenedione, which can upset the body's hormonal balance when it metabolizes into testosterone and estrogen, and may cause premature puberty and stunted growth in adolescents.

* Creatine, a substance produced by the body that can help generate brief surges of muscle energy during certain types of athletic performance. It may also cause kidney problems in susceptible individuals.

* Ephedra, an herbal stimulant that acts like an amphetamine ("speed") and that some investigators hold responsible for dozens of deaths and permanent injuries.

"All you have to do to get these products is walk into a food-supplement store," says Gary Wadler, M.D., a New York sports-medicine specialist and adviser to the White House Office of National Drug Control Policy. That's because a federal law, the 1994 Dietary Supplement Health and Education Act, allows supplements to be sold to consumers of any age without rigorous safety testing and without meaningful oversight of product quality.

Little is known about the long-term safety of these products in adults, and even less about their effect on youngsters. But if the supplement industry has its way, at least some of these products will be consumed by ever-increasing numbers of weekend athletes and even nonathletes.