July 11, 2005
Diet pills hard on the heart
NEW YORK (Reuters Health) - Supplements that contain
ephedra and caffeine-rich guarana, which may be used for weight
loss, result in significant cardiovascular and metabolic
changes, investigators have found. These changes could be
harmful in people with high blood pressure, atherosclerosis
(clogged arteries), or glucose intolerance, a precursor to
diabetes marked by elevated blood sugar. All of these
conditions are strongly associated with obesity.
Even though the US Food and Drug Administration banned
ephedra as a dietary supplement for weight loss, it is still
obtainable as a traditional Chinese medicine, ma huang, the
authors note in the journal Clinical Pharmacology and
Therapeutics. Synthetic ephedrine is also available in
convenience stores and over the Internet. Guarana is an herb
University of California, San Francisco tested the effects of
Xenadrine RFA (a multi-component supplement containing 25.4 mg
ephedra alkaloids and 185 mg caffeine) and ephedra extract
(23.2 mg total ephedra alkaloids) plus guarana (167 mg
caffeine), compared with placebo, in 16 healthy adults.
They report that repeated dosing of ephedra and guarana
produced elevated ephedrine blood concentrations, increased
heart rate and blood pressure, and had unfavorable effects on
glucose and potassium homeostasis.
These effects could exacerbate obesity-related conditions
such as insulin resistance and metabolic syndrome, the authors
This study, they conclude, provides further evidence that
dietary supplements containing ephedra and guarana or
like-compounds could have unfavorable cardiovascular effects,
especially in susceptible individuals such as those with high
blood pressure, glucose intolerance or hardening of the
SOURCE: Clinical Pharmacology and Therapeutics June 2005.