Bitter orange and p-synephrine, the predominant amine in bitter orange, are claimed to increase energy expenditure, facilitate the breakdown of fat and increase glucose uptake by muscles, and is widely used in weight management and sports nutrition supplement.
The ingredient’s profile increased following the FDA ban on ephedra in 2004 as it contains similar compounds and was favored by dietary supplements manufacturers as an ephedra substitute.
P-synephrine is not banned by WADA, the FDA or Health Canada, and the latter recently changed its guidelines and concluded that 1 to 50 mg per day is “not likely to cause any adverse health consequences”.
However, questions about its safety remain, and so scientists from the Jordan University of Science and Technology (Irbid, Jordan) and Creighton University Medical Center (Omaha, USA) assessed the stimulatory effect of the commercial bitter orange extract called Kinetiq (formerly Advantra Z) from Nutratech/Novel Ingredients, Inc. Dr Sidney Stohs, co-author on the paper, is a member of Novel Ingredients’ scientific advisory board.
Data published in Phytotherapy Research indicated that a single capsule of the bitter orange extract with a p-synephrine dose of 49 mg did not significantly change electrocardiograms, heart rates, systolic blood pressure, blood chemistries, or blood cell counts.
A small (4.5 mmHg) decrease in diastolic blood pressure was observed in the p-synephrine group one hour after ingestion of the product, which the authors described as “statistically significant but clinically insignificant”.
The study involved 18 healthy men and women, and the caffeine consumption of the participants was found to vary widely.
“The lack of cardiovascular and stimulant effects agrees with the vast majority of previous studies where bitter orange extract was administered as a single dose and when it has been used in combination with caffeine and other ingredients that have been administered for varying periods of time,” wrote the researchers.
“Furthermore, the lack of cardiovascular effects observed in this study are consistent with results that would be predicted based on previous adrenergic receptor binding studies.
“Longer-term studies are required to determine the effects of bitter orange (p-synephrine) on extended safety and weight loss.”
Source: Phytotherapy Research
May 2016, Volume 30, Issue 5, pages 842–847, doi: 10.1002/ptr.5590
“Cardiovascular Safety of Oral p-Synephrine (Bitter Orange) in Healthy Subjects: A Randomized Placebo-Controlled Cross-over Clinical Trial”
Authors: M. Shara, S.J. Stohs, T.L. Mukattash