New University Study Clarifies Impacts of Bitter Orange in Supplements

A new study on the effects of bitter orange extract on blood pressure and heart rate affirms findings from several other recent studies that show the ingestion of acute Citrus aurantium (bitter orange) does not lead to increased cardiovascular stress. Nutratech’s patented bitter orange ingredient Advantra Z® was the Citrus aurantium used in the research.

The study, titled “The Acute Effects of Citrus aurantium Extract on Blood Pressure and Heart Rate,” also examined the correlation between typical doses (52 mgs) of bitter orange when combined with 704 mg caffeine (equivalent to about nine cups of coffee) over a 24-hour period. The researchers observed no blood pressure or heart rate increases for subjects who used a product containing both bitter orange and caffeine.
The Human Performance Laboratory of St. Cloud State University in St. Cloud, Minn., and the Department of Biology at Colorado University – Colorado Springs conducted the research under the leadership of John G. Seifert, Ph.D., of St. Cloud State.

“Numerous researchers have reported on the influence, or potential influence, of Citrus aurantium on the cardiovascular system,” the report states, “However, these researchers do not make the distinction whether the m- or p-isomers were used in their respective studies and how that would affect physiological and pharmacokinetic responses.” The m-isomer has been shown to raise blood pressure where the p-isomer has not.

“I credit Dr. Seifert and his team for distinguishing between how the m- and p isomers of synephrine impact heart rate and blood pressure,” said Bob Green, president of Nutratech, Inc. “Many researchers overlook the importance of this distinction, but it is critical in understanding how Citrus aurantium works in the body,” he said. “Because Advantra Z has been proven to contain only p-synephrine, users of products containing Advantra Z can rest assured they are ingesting the only proven bitter orange ingredient on the market.”

The researchers further suggested that studies linking Citrus aurantium with elevated blood pressure were likely influenced by other active ingredients in the supplements provided to test subjects rather than the Citrus aurantium itself. “At this point, there seems to be little or no scientific justification to attribute a cardiovascular risk to ingestion of Citrus aurantium, and p-synephrine specifically,” the report stated.

The study also looked at efficacy and noted that fat oxidation following ingestion of Citrus aurantium increased in certain populations of test subjects. “Evidence is emerging that p-synephrine is a thermogenic agent that may have significant weight management benefits when combined with physical activity and caloric moderation,” the researchers said.

The study has been submitted for peer review to The Journal of Nutrition. It was funded by a research grant from Enforma Natural Products.
Nutratech, Inc., provides innovative, proprietary and patented nutraceutical ingredients to the dietary supplement, weight management, sports nutrition, beverage and food industries. The company is headquartered in West Caldwell, N.J. For more information on Nutratech and Advantra Z, visit the company’s web site at

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