US researchers said on Sunday that they had evidence that diet supplements containing the herb ephedra could disrupt heart rhythm and raise blood pressure.
They said volunteers who took a popular diet pill called Metabolife 356 had immediate effects after just one dose.
Although the study was small, it supports reports that ephedra supplements, linked with the deaths of 155 Americans, are dangerous, said Brian McBride, a professor of pharmacy at
the University of Connecticut.
"Millions of people consume herbal supplements in this country every day," he said. Metabolife 356 makes up 40% of the market, he said.
In McBride's study, presented to the American Heart Association's annual meeting, 15 people took a single dose of either Metabolife 356 or a dummy pill. Ephedra, also known as ma huang, acts as a stimulant
Then the researchers did a series of measurements, including taking their blood pressure and taking an electrocardiogram or EKG, which measured heart rhythm.
"Based on our data, these effects are likely sustained over time and would correspond to a nearly 3.5-fold increased risk for the development of a potentially fatal ventricular arrhythmia"
Prof Brian McBride,
University of Connecticut
The researchers found a troubling measurement in a rhythm factor called QT interval. Prolonged QT is linked with fatal heart arrhythmias.
The QT interval increased by 24 milliseconds on average at one, three and five hours after the volunteers took the pill. They had on average a 5% increase in blood pressure.
McBride said 60% of the patients who took Metabolife had the QT prolonged by 30 milliseconds.
"Based on our data, these effects are likely sustained over time and would correspond to a nearly 3.5-fold increased risk for the development of a potentially fatal ventricular arrhythmia," McBride said.
The Bush administration is considering outlawing ephedra because of reports of deaths, strokes, seizures and other serious health problems in people who had taken the product.
But the good news is that you are likely to have success with whichever kind of diet programme you subscribe to.
Doctors said if you properly follow Weight Watchers, the high-fat Atkins diet, the high-protein, or moderate carbohydrate Zone diet, you will lose weight and reduce cholesterol levels.
At the same annual conference, doctors said that the above dieting programmes would yield positive results, but in different ways.
The kind of diet doesn't matter as
long as you follow it, doctors say
"On average, participants in the study reduced their heart disease risk by 5% to 15%," Dr Michael Dansinger of Tufts University in Boston said.
Everyone's a winner
"Instead of saying there is one clear winner here, we are saying they are all winners."
And, as might be expected, the closer dieters followed the plans, the more weight they lost.
Those who stuck it out for a full year lost, on average, 5% of their body weight - or about 4.5 to 5.5 kg.
While the dieters' reduced heart disease "risk factors" such as cholesterol levels, overall blood pressure did not drop much and the study did not last long enough to see if this translated into a lower long-term risk of heart disease.
Instead, the researchers used statistics that show lowering cholesterol by a certain amount, for instance, reduces the risk of heart disease overall.
Dr Robert Eckel of the University of Colorado, who heads the Heart Association's nutrition committee, said the message is clear, lose weight however you can to reduce your risk of heart disease.