The American Herbal Products Association (AHPA) is challenging the conclusions of a new publication that warns that bitter orange dietary supplements pose a risk to consumers. The study, “Citrus aurantium, an ingredient of dietary supplements marketed for weight loss: current status of clinical and basic research,” by Adriane Fugh-Berman and Adam Myers of Georgetown University, was published in the September 2004 issue of the journal Experimental Biology and Medicine.
“This review mistakenly implies that bitter orange supplements are likely to affect drug metabolism,” said Steven Dentali, PhD, AHPA vice president of scientific and technical affairs. “The authors cite references for this effect from bitter orange juice, which is not relevant to the plant parts used in dietary supplements. The fact is that while the juice may have this property, there is no reason to believe that bitter orange extracts, made from the dried fruit or peel, have any such effect. And in fact, one scientific study of 12 human volunteers taking a supplement containing bitter orange found no effect on drug metabolism. ”
The authors also discuss the potential effect of bitter orange on blood pressure. They report that synephrine, a constituent found in bitter orange, raises blood pressure in humans, but their evidence consisted only of one study where the pure chemical was administered by continuous intravenous infusion at the rate of 4 mg/minute.
“Research on intravenous administration of purified synephrine is not directly applicable to oral consumption of bitter orange extracts in dietary supplements,” added Dentali. “The authors do cite one study on the effect on blood pressure of a dietary supplement containing bitter orange, but this research found no effect on blood pressure after 6 weeks of use.”
Nevertheless, a sensational press release generated by Georgetown University blurred the distinction between synephrine and bitter orange extract, and quoted one of the authors as stating, “C[itrus] aurantium has many of the same potential deleterious cardiovascular effects as ephedra,” in spite of the fact that there is no such conclusion in the article itself.
“There is one point on which we may all agree,” said Dentali, “and that is that more research on this herb would be welcome. But critical interdisciplinary thinking — espoused by these authors— should begin with consideration of the ingredient that consumers are actually taking.”
1 Gurley et al. Assessment of Botanical Supplementation on Human Cytochrome P450 Phenotype: Citrus aurantium, Echinacea, Milk Thistle, Saw Palmetto. Clinical Pharmacology and Therapeutics 2004;75(2):P35.
Source: American Herbal Products Association (AHPA)