Narrator: This is Science Today. A University of California, San Francisco study is calling on the Food and Drug Administration to develop dose guidelines and warning labels for popular dietary supplements that contain a stimulant called ephedrine. Researcher Christine Haller says about 12 million Americans use these products to boost energy levels or to lose weight.

Haller: It contains ma huang, which is an herbal form of ephedrine and caffeine. And these two products in combination seem to be potentially more dangerous in causing adverse effects - a sense of nervousness, of jitteriness, nausea and vomiting. But it could be more serious - chest pain indicates a possibility of having a heart attack or stroke.

Narrator: In an unregulated industry, Haller says consumers usually don't know the risks.

Haller: When a drug goes through FDA approval, they have post-marketing surveillance so that when there are adverse effects reported, the news gets out real rapidly. But in an unregulated industry, there's really no way - except for anecdotal report to find out what's dangerous and what isn't.

Narrator: For Science Today, I'm Larissa Branin.