Ephedra-Free Weight Loss Supplements â€“ Cardiovascular Risk?
Ephedra-free weight loss dietary supplements may not be as safe as previously thought. A recent study shows that these supplements may pose cardiovascular risks identical to some that caused products containing ephedra to be banned, according to a report by MedPage Today on 12 September.
Researchers have shown that bitter orange extract â€“ a substance used to replace ephedra in weight-loss products â€“ seems to raise blood pressure and increase heart rate when taken in combination with other stimulants.
Results of the research, carried out by Christine A. Haller, MD, and colleagues at the University of California San Francisco (UCSF), were reported in the September issue of the American Journal of Medicine.
Bitter orange (Citrus aurantium), also known as Bigarade Orange or Neroli, is a botanical source of adrenergic amines octopamine and synephrine, which are similar in structure to the neurotransmitter norepinephrine. The pharmaceutical usage of synephrine is for the treatment of blood pressure and nasal congestion, MedPage Today reported.
Researchers at UCSF carried out a randomized, double-blind, placebo-controlled study testing two different weight-loss supplements containing bitter orange extract: Advantra Z and Xenadrine EFX. Advantra Z contains almost 15.6 milligrams of synephrine per capsule, while Xenadrine EFX contains 2.7 milligrams of synephrine, 2.9 milligrams of octopamine, and nearly 120 milligrams of caffeine (equivalent to three cups of coffee, according to MedPage Today).
Ten healthy, non-smoking adults participated in the study, which administered single doses of Advantra Z and Xenadrine EFX or placebo. Researchers recorded blood pressure and heart rate measurements before dosing and at regular hourly intervals afterward.
Results & Conclusions
Compared with placebo, Advantra Z increased heart rate by average of 11 beats per minute above baseline measurements at six hours after dosing. Xenadrine EFX increased participantsâ€™ heart rate an average of 16 beats per minute at six hours after dosing.
Blood pressure measurements showed that Advantra Z did not raise blood pressure. However, Xenadrine EFX, which contains additional stimulants, increased blood pressure (both systolic and diastolic) by an average of about 9 mmHg two hours after dosing. Researchers suggested that, although synephrine alone does not seem to increase blood pressure, it may accentuate the ability of other stimulants â€“ such as caffeine â€“ to raise blood pressure. They also noted that further studies are required to determine the long-term effects of these products.
"Until such data are available, physicians should caution patients about the use of ephedra-free weight-loss dietary supplements, and monitor blood pressure in those who choose to use these supplements," the researchers said, according to MedPage Today. "Individuals with hypertension, heart disease, or other pre-existing conditions that could be exacerbated by the sympathomimetic effects of botanical stimulants should avoid use of these products."
- Ephedra-Free Supplements Not Necessarily Risk-Free, MedPage Today, 12 September 2005
- Hemodynamic effects of ephedra-free weight-loss supplements in humans, Haller CA et al., The American Journal of Medicine, 9 September 2005.
Posted: September 2005