As a “chemical cousin” of ephedra, synephrine has replaced the ephedra content of many popular fat burners (ephedra now being illegal, of course). It appears in fat burners as “synephrine HCl”, or it can be derived from Citrus aurantium, also known as “bitter orange.” The patented form of synephrine is known as “Advantra Z™”. Regardless, if you see any of these on the label of the fat burner you’re investigating, then it’s synephrine we’re talking about.
Retailers claim synephrine offers all the “fat burning” benefits of ephedra without any of the annoying side effects — sleeplessness, “the jitters”, elevated blood pressure and heart rate, etc., etc.
Unfortunately, the evidence to support these claims is a bit sparse.
First of all, there are studies that show synephrine-containing products do elevate blood pressure and heart rate, despite claims that it is not a stimulant (see Ann Pharmacother. 2006 Jan;40(1):53-7. Epub 2005 Nov 29).
And it’s fat burning characteristics?…
This study (Obes Rev. 2006 Feb;7(1):79-88) concludes…
“While some evidence is promising, we conclude that larger and more rigorous clinical trials are necessary to draw adequate conclusions regarding the safety and efficacy of C. aurantium and synephrine alkaloids for promoting weight loss.”
And this one (Am J Cardiol. 2004 Nov 15;94(10):1359-61) on the “Safety and efficacy of Citrus aurantium for weight loss” concluded…
“An extensive search of MEDLINE, EMBASE, BIOSIS, and the Cochrane Collaboration Database identified only 1 eligible randomized placebo controlled trial, which followed 20 patients for 6 weeks, demonstrated no statistically significant benefit for weight loss, and provided limited information about the safety of the herb.”
One study (“Increase in the thermic effect of food in women by adrenergic amines extracted from Citrus aurantium“) performed at the University of McGill in Montreal and published in Obesity Research (Obes Res. 2005 Jul;13(7):1187-94.) was slightly more positive. But although it concluded that Citrus aurantium did not have any effect on blood pressure and pulse rate, and did elevate the metabolism, the results were hardly earth-shattering…
“CA (Citrus aurantrium) alone increased thermogenesis, on average, by 4% (52), a response that is statistically significant but not necessarily clinically significant, representing an average 1 kg over 6 months.”
Sadly, the fat burning effects of synephrine have been largely exaggerated by the supplement industry (surprise, surprise!). The data currently available for synephrine indicates some promise and a very minor positive effect, but it’s hardly earth shattering.
At the same time, anecdotal reports suggest synephrine may be helpful as an appetite suppressant, but this has yet to be firmly established by credible studies.
Bottom line on synephrine?
For any fat burner that contains synephrine in a supportive role, it’s probably not the end of the world. It does offer some minor benefits, and may work as a appetite suppressant. But if the fat burner is basing its claims upon the fat burning powers of synephrine…
Look out! There’s no evidence to support dramatic results!
For those of you interested in its possible appetite suppressing characteristics, good news; you can experiment with synephrine very cheaply (around $12 at BodyBuilding.com for 180 caps, or a 2 months supply). At this price, it might be worth an experiment.