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."
To learn more about how to evaluate a weight-loss product, visit American Dietetic Association.
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
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