Diet Supplement Linked to Heart ProblemOct 10, 2003 | www.webmd.com A single Metabolife 356 pill can cause changes in heart rhythm that increase the risk for developing a dangerous and potentially lethal irregular heart beat, according to new research presented at the American Heart Association meeting here.
Moreover, that single pill also significantly increases blood pressure, says Brian F. McBride, PharmD of Hartford Hospital, Division of Cardiology and Drug Information at the University of Connecticut School of Pharmacy in Hartford, Conn.
McBride tested 15 healthy volunteers, average age 26, to determine the immediate effects of the popular diet pill. He measured heart function by taking blood pressure and electrocardiogram (ECG) measurements at one, three and five hours after the volunteers took the pill.
On ECG, the pill was associated with a delay in the electrical signals that control heart beats. This delay can cause abnormal electrical currents to be sent to the main pumping chambers of the heart, which, if untreated, can be fatal, says McBride.
'This delay was consistent at one, three and five hours,' he tells WebMD at an AHA press conference. 'A single pill is just a third of the recommended three-pill daily dose.'
Systolic blood pressure, the top number in blood pressure measurement, jumped 10 points at one hour and continued to climb so that is was up an average of 16 points by three hours after taking the pill, says McBride. Diastolic pressure the bottom number was up more than five points at an hour but gradually declined so that at three hours it was just two points higher.
Metabolife 356 contains ephedra as well as 17 other ingredients and while other studies have targeted ephedra as a dangerous element McBride is not so sure that is the case here.
'We don't really know if ephedra is responsible for these changes, it is possible that another ingredient is responsible. We need to safety test all ingredients,' he says.
James J. Ferguson III, MD, FACC, associate director of clinical cardiology research at The Heart Institute in Houston, Texas, tells WebMD that the study is interesting 'but I don't think it means that we should ban Metabolife based on this one study. I do think it indicates the need to test Metabolife and all these supplements for safety. I think safety testing of all ingredients is necessary.' Ferguson was not involved in the study.
McBride says he is not advocating a Metabolife ban, but he does support 'doing the same type of safety testing in these products that the FDA requires for pharmaceuticals.' Dietary supplements are regulated as foods, and not prescription drugs, and therefore do not need FDA approval to be marketed.
Additionally, he says it is impossible to determine if the results associated with a single dose would 'worsen or improve with continued use.'
But co-researcher Jeffrey Kluger, MD, tells WebMD that the ECG results seen with a single dose of pharmaceuticals generally don't change with repeated doses. 'So the single dose response [seen with Metabolife] does, in my opinion, predict long term outcome,' he says.
WebMD unsuccessfully tried to contact a Metabolife representative for comment.