Only a year and a half after the Food and Drug Administration (FDA) banned the sale of diet supplements containing ephedra, bitter orange peel is becoming increasingly popular as a substitute for that appetite suppressant.
A new study from the University of California, San Francisco has shown, that in similar doses, bitter orange alone is not as potent as ephedra. In the 10 experimental subjects who tried it, bitter orange increased the heart rates, but not as much and not for as long as ephedra, said Dr. Christine Haller, an assistant professor of medicine who led the study.
The drug may have some dangerous effects, however. The same study reports that when bitter orange peel is combined with caffeine, as it is in many diet pills promoted as “ephedra free,” it can raise the heart rate and the blood pressure as it did in the 10 healthy subjects who were between 19 and 42.
The researchers had not expected to see a significant increase in blood pressure in a study with only 10 people and, thus, regarded the finding as “amazing.”
In the study, participants were given the ephedra-free supplements Advantra Z, which contains bitter orange alone, and Xenadrine EFX, which at the time of the study contained bitter orange along with vitamins and minerals and caffeine equal to two large cups of coffee. (Cytodyne, the company that makes Xenadrine EFX, no longer uses bitter orange.)
Although the Advantra Z had 15.6 milligrams of synephrine (the main active ingredient in bitter orange) and the Xenadrine EFX 2.75, only the Xenadrine EFX raised blood pressure.
According to researchers, the increase could not be caused entirely by the caffeine, because although caffeine can boost systolic blood pressure (when the heart beats), it does not affect diastolic blood pressure (when the heart is at rest).The Xenadrine EFX increased both.
Whether the blood pressure problems caused by pills are triggered by the caffeine, the bitter orange or a combination of the two, experts agree that taking the pills is probably not worth the health risk.
The F.D.A. does not require manufacturers of dietary supplements to prove that the products are safe and effective before they are sold. Adam Myers, a professor of physiology and biophysics at Georgetown University Medical Center in Washington, who recently reviewed the research on the supplement, said "There are no clinical studies that show it’s an effective weight loss agent."
Dr. Jonathan Waitman, a specialist in internal medicine and clinical nutrition at the Comprehensive Weight Control Program at NewYork-Presbyterian/Weill Cornell Hospital, said the study illustrated the risks involved with over-the-counter diet pills.
"My take-home point would be that you don’t know what you’re getting when you take one of these supplements," Dr. Waitman said. "There’s no way for the consumer to use caution other than not to buy these at all."