Some of the weight-loss aids that have quickly emerged to replace the now-banned substance ephedra may carry risks of their own, a small study suggests.
Researchers at the University of California, San Francisco found that two ephedra-free diet supplements increased the heart rates of 10 healthy volunteers, and one also raised their blood pressures. These effects are similar to what has been seen with ephedra, an herbal stimulant that was banned in the U.S. last year after reports linked it to heart attacks, strokes and at least 155 deaths.
The supplements, sold as Advantra Z and Xenadrine EFX, both contain extracts of bitter orange, known scientifically as Citrus aurantium. The botanical, which has long been used in traditional Chinese medicine for digestive problems, has emerged as one of the major replacements for ephedra in over-the-counter weight-loss products.
Citrus aurantium contains a compound called synephrine that, like ephedra, stimulates the central nervous system and may boost metabolism.
But there has been little research to show that supplements containing bitter orange extract are either safe or effective, Dr. Christine A. Haller, the lead author of the new study, said in an interview.
The blood pressure and heart rate effects she and her colleagues found may not pose a problem for healthy people, Haller said, but the concern is with those who have elevated blood pressure, or conditions such as diabetes -- as many overweight and obese people do.
'People should use caution'
“This does indicate that people should use caution,” Haller said, particularly since there’s no clear evidence that the products provide any benefit.
For their study, reported in the American Journal of Medicine, the researchers had 10 healthy adults take Advantra Z, Xenadrine EFX and a placebo on three separate occasions. They then measured participants’ short-term cardiovascular responses.
Compared with the placebo condition, Xenadrine boosted volunteers’ blood pressure by between 9 and 10 points, on average, the study found. In contrast, Advantra did not appear to affect blood pressure.
And with both products, participants showed elevated heart rates 6 hours after taking the supplement.
Advantra Z contains only bitter orange extract as its active ingredient, which suggests, Haller said, that the synephrine in these diet aids does not itself raise blood pressure. The Xenadrine product contained a mix of bitter orange extract, caffeine and various herbs -- pointing to the combined effects as the culprit behind the blood pressure elevation.
Until more is known about the safety and efficacy of herbal diet aids, people should not assume that ephedra-free means risk-free, according to Haller.
The problem, she said, is that people perceive these products as “natural,” and therefore safe. “But they really should be treated as drugs,” she said.
That, according to the researcher, means seeing a doctor before taking any over-the-counter diet pills.