Seeking to Shed Fat, She Lost Her Liver

"It was like you're doing aerobic exercise while you're just sitting there," said Jennifer Rosenthal, 28, a truck dispatcher and the mother of a 4-year-old in Long Beach, Calif.

The capsules, sold over the Internet at $39.95 for a bottle of 90, had just one ingredient, usnic acid, a chemical found in certain species of lichen plants. The chemical is not approved for any medical use, but the label on the bottle said it would make the body burn calories "at an accelerated rate."

In early October, Ms. Rosenthal began swallowing four 125-milligram capsules a day, half the maximum dose recommended on the label. She took them for two weeks, skipped two weeks as the label directed, and then started again. She was not overweight; she just wanted to stay in shape. She took the capsules for a total of 17 days.

By Nov. 8, Ms. Rosenthal was in a coma, connected to a respirator and a web of tubes, her skin a dusky yellow.

Her liver had failed, and her swift decline put her at the top of the waiting list for a transplant at the University of California at Los Angeles. On Nov. 12, a liver became available from a cadaver.

Without it, Ms. Rosenthal's surgeon said, she would probably not have lasted another day. Her liver was so badly damaged that it had shriveled to about a third of what it should have weighed.

Ms. Rosenthal's doctors said they thought usnic acid was almost certainly to blame. Before taking it, she had been perfectly healthy, and they could find no other explanation for her illness. But the doctors said they did not know how the chemical could have killed so many liver cells so quickly.

"This is a young woman who almost lost her life," said Dr. Ronald W. Busuttil, her surgeon. "Although she's got her life back now, she has to be under life-long medical care. Her life has been altered forever. The fact that you can get these things over the Internet is mind-boggling."

Usnic acid is one of hundreds of substances sold either alone or with other ingredients as "dietary supplements," a loosely regulated category of products that includes vitamins, minerals, herbs, amino acids, enzymes and other chemicals found in plants and foods. Though many are harmless and some may be beneficial, others have been linked to serious health problems.

Among the most notorious is another substance promoted for weight loss, ephedra, which is suspected of playing a part in the death of Steve Bechler, a 23-year-old pitcher for the Baltimore Orioles who collapsed during a workout on Feb. 16 and and died the next day in a Fort Lauderdale hospital.

The Food and Drug Administration has received more than 100 reports of deaths among ephedra users, as well as 16,000 reports of other problems, including strokes, seizures, heatstroke, heart disorders and psychotic episodes.

On Friday, the government called for new labels for ephedra to warn consumers of the risk of heart attack, stroke and death. Tommy G. Thompson, the secretary of health and human services, said he was considering banning ephedra outright. But by law, the government must prove an unreasonable risk of harm to ban a dietary supplement.

The true extent of illness caused by supplements is not known, because while the worst cases attract attention, less serious ones may go undiagnosed or unreported. The F.D.A. itself estimates that it gets reports on fewer than 1 percent of the severe adverse effects linked to dietary supplements.

A study published in January based on 489 reports to American poison control centers in 1998 found that various supplements were also implicated in heart attacks, bleeding, seizures and deaths.

The supplement industry, with sales of more than $17 billion a year, is so loosely regulated that products can be marketed without the proof of safety and efficacy required for drugs by the food and drug agency, which cannot take a supplement off the market unless there is proof that consumers have been harmed. As long as manufacturers do not claim that their products can be used to treat or cure disease, they are not regarded as drugs.

"With supplements, the burden of proof is on the agency to show a product is unsafe," said Monica Revelle, a spokeswoman for the F.D.A. "We have to prove a causal link."

F.D.A. officials declined to discuss usnic acid, Ms. Revelle said, except to say that they were "monitoring it very closely."