A new study shows the popular dietary supplement Metabolife 356, which contains both ephedra and caffeine, caused almost immediate increases in blood pressure as well as changes in heart beats that could be potentially fatal.
The FDA announced a ban on the popular diet supplement ingredient ephedra, also known as Ma Huang, on Dec. 30, 2003 and warned consumers to immediately stop buying and using ephedra products.
One Dose May Be Deadly
Researchers say many people are drawn to herbal weight-loss preparations, such as those containing ephedra, because natural products are perceived as safe.
"Unfortunately, the perception of safety may be the result of a lack of data," write researcher Brian F. McBride, PharmD, of the University of Connecticut Schools of Pharmacy, and colleagues.
Questions regarding the safety of ephedra products had been raised by anecdotal cases of sudden cardiac death and stroke, but few studies have examined the safety of these products.
In the study, published in the Jan. 14 issue of the Journal of the American Medical Association, researchers looked at the effects of a single dose of Metabolife 356 containing 12 milligrams of ephedra and 40 milligrams of caffeine in 15 healthy adults. Researchers measured the participants' heart rates and blood pressure before taking the supplement or a placebo, then again one, three, and five hours afterward.
The study showed that after taking a single dose of the supplement the volunteers had higher systolic (the top number of a blood pressure reading) blood pressure (123.5 vs. 118.83 mm Hg) compared with those who took the placebo.
In addition, those who received the single dose of ephedra supplement had a longer QTc interval, which is a measured interval on an electrocardiogram. When prolonged this can lead to abnormal heart contractions.
A QTc interval of longer than 30 milliseconds has been cited as a possible cause of potentially fatal irregular heartbeats that result in sudden cardiac death. Researchers found that 53% of the participants had QTc intervals of at least 30 milliseconds while taking the dietary supplement containing ephedra and caffeine.
Researchers say that since the actual ingredients in Metabolife 356 responsible for these results are not known, people should avoid these and other similar dietary supplements until more information is known about their safety.