Two common weight loss supplements promoted as ephedra-free and safe for dieters caused increased heart rate among healthy people

Sep 10 2005

Two common weight loss supplements promoted as ephedra-free and safe for dieters caused increased heart rate among healthy people, and could have harmful health effects in some people, according to a study by University of California - San Francisco (UCSF) scientists. Their placebo-controlled clinical study is the first to examine the pharmacological effects of these re-formulated dietary supplements.

The research examined the effects on blood pressure and heart rate of two dietary supplements containing bitter orange extract -- a substance that has rapidly replaced ephedra in weight-loss products since it was banned by the FDA in 2004 because of concerns about serious health effects.

The study involved 10 healthy adults given single doses of one of the two supplements or a placebo. The two supplements tested were Advantra Z and Xenadrine EFX. Single doses of both products increased heart rate by an average of 11 to 16 beats per minute over baseline, the scientists found. This would be the equivalent of an 18 percent increase if baseline rate is 80 beats per minute.

In addition, Xenadrine EFX also significantly increased blood pressure by 7 to 12 percent (9-10 mm Hg), the researchers reported. Xenadrine EFX appears to have similar acute cardiovascular stimulant actions as banned ephedra products, according to their report.

"These findings indicate that ephedra-free dietary supplements could have some of the same adverse health effects associated with previously available ephedra products, such as Metabolife 356 and Ripped Fuel," said Christine Haller, MD, UCSF assistant professor of medicine and lead author of the paper.

The scientists call for further research on the safety and effectiveness of bitter orange- containing supplements -- particularly among those most likely to take them: overweight people who may have other health conditions.

The research is published in the September issue of The American Journal of Medicine, available September 9.

Bitter orange extract, or Citrus aurantium, is extracted from the dried fruit peel of bitter orange. Known in Chinese herbal medicine as Zhi shi, it is a traditional remedy for gastrointestinal ailments, the scientists said.

The predominant constituent of bitter orange is synephrine, which in pharmaceutical form is commonly used to treat low blood pressure and nasal congestion.

Advantra Z contains only bitter orange, while one dose of Xenadrine EFX contains several other ingredients, including caffeine equivalent to the amount in 3 cups of coffee, the researchers found. The increased blood pressure from taking Xenadrine EFX is likely not due to caffeine alone, they concluded, but potentially related to the actions or interaction of other constituents in the multi-ingredient supplement.

The scientists call for longer term dosing studies to determine whether the blood pressure effects of Xenadrine EFX persist with repeated use. Until such data are available, they conclude, doctors should caution patients about using ephedra-free weight-loss dietary supplements and should monitor blood pressure in those who choose to use the products.

In particular, people with hypertension, heart disease or other pre-existing conditions that could be aggravated by the supplements should avoid them.

"Consumers should be aware that ephedra-free dietary supplements have not been extensively tested for safety and the health effects are not well known," Haller noted.

Among other physiological measures, heart rate and blood pressure were recorded in the study for an hour before dosing and then at several intervals afterwards.

To rate physical symptoms, moods and emotions, questionnaires were administered one, two and six hours six hours after taking the supplements or placebo.

The caffeine-containing Xenadrine EFX product also increased alertness according to responses on the questionnaire. But neither product appears to have a significant effect on mood, the study found.

Co-authors on the study with Haller were Neal Benowitz, MD, professor of medicine and of clinical pharmacy at UCSF, and Peyton Jacob III, PhD, a researcher in psychiatry at UCSF.