Last February, Mark McClellan, the head of the Food and Drug Administration, conceded that "serious adverse events from ephedra appear to be infrequent." Yet at the end of December, he announced that the FDA planned to ban all dietary supplements containing the herbal stimulant, saying they pose "an unreasonable risk."

Casual observers could be forgiven for assuming that McClellan had changed his mind in light of new evidence. But nothing has happened during the last 10 months to indicate that his initial assessment of ephedra's hazards was off the mark.

In fact, even as the FDA insists that "consumers should stop buying and using ephedra products right away," it admits the supplements do not constitute an "imminent hazard." Its rule banning them is to be published in a few weeks and take effect 60 days later -- not the pace you'd expect if ephedra were killing people left and right.

The key to understanding this puzzle is the FDA's interpretation of "unreasonable risk," the standard for removing a product from the market under the Dietary Supplement Health and Education Act of 1994. "In FDA's view," the agency explains, "'unreasonable risk' implies a risk-benefit calculus" to determine "whether the product's known or suspected risks outweigh its known or suspected benefits."

If the FDA allowed consumers to make this judgment for themselves, different people would weigh ephedra's risks and benefits differently, and some might decide to accept the former in exchange for the latter. To prevent such chaos, the FDA's experts on what's best for you are stepping in to forcibly impose their judgment on the entire nation.

The FDA gives short shrift to ephedra's benefits, saying there is "little evidence of ephedra's effectiveness except for short-term weight loss" -- a use it apparently considers frivolous, despite the health risks associated with excessive weight. The FDA does not mention ephedra's utility in boosting energy and concentration, although these stimulant effects are valued by many users, or in treating allergies and colds, although the plant has been used as a decongestant for thousands of years.

Since the FDA sees ephedra's benefits as trivial, it is inclined to see any risk at all as "unreasonable." It's enough to note that ephedra "raises blood pressure and otherwise stresses the circulatory system."

Yet as McClellan noted early last year, such effects rarely have serious consequences. A comprehensive, FDA-commissioned review by the RAND Corp. that considered every adverse reaction recorded in the agency's files and the medical literature through 2002 identified only 20 cases of serious symptoms among ephedra users where there was an attempt to rule out alternative explanations.

These "sentinel events" included two deaths, "four myocardial infarctions, nine cerebrovascular accidents, one seizure, and three psychiatric cases." The FDA noted that even these reports "do not prove that ephedra caused the adverse event ... Other unmeasured factors may have contributed, and such serious adverse events are likely to happen (albeit at very low rates) among the millions of users of ephedra anyway." Continued...