Weight loss supplements that have been advertised as being safe may cause harmful health effects in some people, according to a recent study.
These products -- which are promoted as being ephedra-free and safe for dieters -- have been shown to cause increased heart rate among healthy people and harmful health effects in some people, report scientists who worked on the study.
The study by University of California San Francisco is the first to examine the effects of these re-formulated dietary supplements. Researchers examined the effects on blood pressure and heart rate of two dietary supplements containing bitter orange extract.
Bitter orange extract has commonly replaced ephedra in weight control products since ephedra was banned by the FDA in 2004 due to concerns about health risks and side effects.
The UCSF 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. 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 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 and suggest 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 health condition that could be worsened by the effects,such ashypertension, heart disease or other pre-existing conditions should avoid the supplements.
"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.
The research is published in the September issue of The American Journal of Medicine.
This article was adapted from a news release provided by The National Institutues of Health.