May 15 (HealthDay News) -- Weight-loss supplements widely available for purchase online often include ingredients that are potentially hazardous to your heart, and a new study shows the labels often don't include this warning.

One of the hazardous ingredients that was found in the products has been banned on the U.S. market since 2004, according to study author Dr. Alireza Nazeri, an internist and cardiology research fellow at the Texas Heart Institute at St. Luke's Episcopal Hospital, in Houston.

The study was expected to be presented Thursday at the Heart Rhythm Society's annual meeting, in San Francisco.

Nazeri and his colleagues reviewed the ingredients of 12 different brands of weight-loss supplements. They found the brands by entering the common search terms "diet pills" and "weight-loss supplements" into popular Internet search engines, including Google, MSN and Yahoo.

"We were trying to find out if the weight-loss supplements have any ingredients with life-threatening cardiac side effects," Nazeri said.

Next, they made a list of the ingredients on each label. In all, there were 60 different ingredients, for an average of 7.25 ingredients per bottle. Most were herbal extracts, while others were minerals, vitamins and other substances.

Next, the researchers scoured medical databases, including Medline, Pubmed and Natural Medicines Comprehensive Database, to find out if there was any significant association between the ingredients and cardiac problems.

They identified 11 ingredients with at least one report of life-threatening cardiac side effects. Eight of the 12 brands contained a potentially hazardous ingredient.

To their surprise, the researchers found one brand included ma huang, also known as Chinese ephedra, even though the U.S. Food and Drug Administration banned it in 2004.

The other ingredients that may be potentially dangerous to the heart included: bitter orange, Camellia sinensis, green tea, buckwheat, guarana, Korean ginseng, licorice root, Synephrine HCl, caffeine anhydrous and citrus aurantium.

"We are not releasing any names of products," said Nazeri. "That was part of our protocol."

The products chosen may be just the tip of the iceberg, and releasing the names may give people the idea the problem is confined to just those brands, said study senior author Dr. Mehdi Razavi, director of the institute's clinical arrhythmia research lab and a clinical associate professor of medicine at Baylor College of Medicine, in Houston.

The study results make sense to Elisa Odabashian, director of the West Coast office of Consumers Union, publisher of Consumer Reports. "It doesn't surprise me at all," she said.

Especially dangerous, she said, is that people often combine these products with coffee or other caffeine-containing drinks, which affect the heart even more.

Odabashian worked on efforts to get ephedra-containing products banned in California. Her advice for consumers thinking of buying weight-loss products over the Internet? "I think it's a crapshoot. I don't think you should be doing it."

SOURCES: Alireza Nazeri, M.D., internist and cardiology research fellow, Texas Heart Institute, St. Luke's Episcopal Hospital, Houston; Mehdi Razavi, M.D., clinical associate professor, medicine, Baylor College of Medicine, Houston, and director, clinical arrhythmia laboratory, Texas Heart Institute, St. Luke's Episcopal Hospital, Houston; Elisa Odabashian, director, West Coast office, Consumers Union, San Francisco; May 15, 2008, presentation, Heart Rhythm Society annual meeting, San Francisco