Burkhard Bilger and his wife never had heard that the ancients used the herb pennyroyal to induce abortion. They just liked the tangy mint taste of pennyroyal tea - until she discovered she was two months pregnant, and her doctor asked her to avoid caffeine.

Soon after, Jennifer Bilger had a miscarriage.When he learned the tea may have been to blame, "I was horrified," said Bilger, a New York science editor who contends supplements don't come with proper warnings. "There are a lot of very potent herbs out there. You go into a food co-op, and you don't know what you're getting."

An Associated Press analysis of Food and Drug Administration records suggests Bilger's experience is not uncommon: The agency has logged more than 2,500 reports of side effects and 79 deaths associated with dietary supplements.

About 900 of the illnesses and 44 deaths involved people taking herbal products that contain ephedrine-like stimulants. Other possible culprits range from "diet teas" to hormones like DHEA and even high-dose vitamins.

Millions of Americans take dietary supplements, particularly the herbs that are the fastest-growing segment. They spent $3.2 billion last year.

Supplements promise they'll slow aging, improve memory, clean kidneys, protect the heart, even prevent cancer.

There is evidence that certain herbs, vitamins and minerals do help. Folic acid prevents birth defects. Calcium wards off osteoporosis. Many scientists agree that garlic may help lower cholesterol, ginger calms nausea, and valerian is a mild sleep aid. The National Institutes of Health is studying whether St. John's wort is an anti-depressant.

But scores of other products have sparse, if any, data to support claims that even some in the industry call exaggerated. The pills, tonics and teas sell with little to guide consumers about what actually works or potential side effects.

"You almost have to be a detective," said Mary Ellen Camire, food sciences chief at the University of Maine, who studies natural remedies.

Most such products do not raise safety concerns, said Elizabeth Yetley, FDA's chief of special nutritionals, but the agency has listed 16 supplements as risky.

"You're self-medicating," notes Mark Blumenthal of the nonprofit American Botanical Council. "People should learn how to use these products properly."

The boom in dietary supplements dates to 1994, when Congress shielded them from most government oversight. They sell without prior certification or purity inspections.