WEST CALDWELL, N.J.—Bitter orange (Citrus aurantium) and its main constituent, p-synephrine, are not associated with adverse events such as increased heart rate and blood pressure, but is linked to weight management benefits including increased metabolism and energy when taken for six to 12 weeks, according to a new research review. Scientists from Georgetown University Medical Center, Washington DC, Creighton University, Omaha, and the University of Science and Technology, Irbid, Jordan, looked at published and unpublished studies on bitter orange and published their findings in the September issue of the International Journal of Medical Sciences (9(7):527-538).
The team reviewed more than 20 studies involving a total 360 subjects who consumed bitter orange/p-synephrine alone (44 percent of subjects) or in combination with other ingredients (56 percent) each day for at least 12 weeks. More than half of the subjects were obese or overweight, about two-thirds of whom also consumed 132mg to 538mg caffeine daily.
The reviewers found no significant adverse events, such as increased heart rate or blood pressure, among those taking bitter orange alone or in combination formulas. The ingredient's use, alone or in combo, was also not associated with alteration in electro-cardiographic data, serum chemistry, blood cell counts or urinalysis.
Two of the author's— Sidney J. Stohs, Ph.D., (Creighton)and Harry G. Preuss, M.D., (Georgetown) are among the United State's most expert researchers on natural performance-enhancing ingredients, according to Nutratech, which noted their review considered 56 clinical research studies and other reference sources.
The company, which makes Advantra Z® bitter orange, further pointed out the review article talks about why there are no negative cardiovascular side effects, including specifics on p-synephrine receptor binding. "Properties possessed by m-synephrine are inappropriately attributed to bitter orange extract and p-synephrine, and clinical case study reports and reviews involving bitter orange extract frequently make inappropriate references to m-synpephrine," they explained—often found in nasal decongestants and sprays, m-synephrine (phenylephrine) has the potential for raising blood pressure in humans.
Last year, Preuss and Stohs published a similar review in the American Botanical Council's Herbalgram (2011;89:34-39), reaching the same conclusion. However, FDA reported last month its own study of bitter orange found it raised blood pressure in rats. Bob Greene, president of Nutratech, noted FDA's study used bitter orange doses that were 13- to 43-times higher than the typical human dose. he also explained low amount of heart rate and blood pressure increases in FDA's study were not statistically significant.
Dr. Stosh recently presented a webinar on bitter orange, "A Safe Alternative to DMAA and Other Problem Diet/Fitness Ingredients: A Fresh, Scientific Look at an Established Ingredient," available on-demand .