You may have seen it added to the formula of dietary and training supplements as Bitter Orange or Citrus Aurantium. These are actually the same thing, but Synephrine is the bioactive compound for which they have been included in the recipe. Present in one fruit at high enough concentration to use – the Bitter Orange (aka Citrus Aurantium) – synephrine is both a fat-burner and a stimulant.
The combined effects of both fat-burning and neural stimulation even earns Synephrine the right to be in the category of performance enhancers. Often it is found in weight loss pills, fat-burners and other diet products, though in recent times it has become an increasingly popular component of pre-workout supplements as part of an overall combination incorporating several ingredients to help maximize the results from resistance training.
When synephrine is discussed, it’s almost always the parasynephrine, or p-synephrine, variant that is being referred to. It’s also the most common to be included in diet pills and supplements as it is more effective than m-synephrine and o-synephrine.
Synephrine Production in the Human Body
We produce synephrine in small amounts naturally. This endogenous synthesis derives from the metabolism of octopamine – a trace amino acid, which is itself a metabolite of tyramine. Therefore natural synephrine synthesis in the body is the end result of tyramine metabolism.
Synephrine Production in Nature
Citrus Aurantium / bitter orange is a bitter tasting fruit, rarely eaten for that reason. The fruit is the only real viable source of synephrine due to the high concentration, though the compound is present in many other citrus fruits in small quantities.
Similar to the compound ephedrine, synephrine can raise the metabolism of its user and induce a thermogenic effect. This basically means that fat is made more readily available to be used as fuel, and thus oxidized (burned) at a higher rate.
The fat-burning behaviour of synephrine is independent to the dietary intake of the consumer, though a calorie controlled diet will of course create more of a deficit and result in greater fat loss.
Synephrine’s fat-burning effects work over a long period. Due to its high level of safety it is a good choice for extended use.
Also similar to ephedrine, synephrine is a stimulant, interacting with the epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine neurotransmitters.
Cognitive function, focus, drive and energy are all increased in the subject. Unlike the fat-burning mechanism however a tolerance can eventually build to the stimulation effect. A couple of weeks of ‘downtime’ from the supplement in question should drop those levels. This is essentially why some supplements should be cycled after approximately 12 weeks of use, though this is not a hard rule and the directions on the packaging should be followed regardless.
Some studies have implied that synephrine can increase the thermic effect (cellular heat) of food, though more research is needed to confirm this absolutely. Preliminary evidence has been correct for other aspects of the ingredient though, so it looks good.
Why not Ephedrine?
Ephedrine has been mentioned a couple of times because of synephrine’s similarity with it. It does NOT however have the same effect on blood pressure as ephedrine, which can raise it significantly. For this reason Synephrine is recommended over ephedrine.
Stacking with Other Ingredients
The old ephedrine-cafffeine-aspirin (ECA) stack was a potent fat-burner but is no longer recommended for safety reasons.
The safer version due to synephrine’s similarity with the positive effects of ephedrine; and white willow bark’s similarity to aspirin (it contains salicylic acid as opposed to acetylsalicylic acid) is the synephrine-caffeine-salicin stack.
Aside from caffeine and white willow bark, it would go well with L-theanine, which smooths out the stimulatory effects of other ingredients while enhancing their cognitive effects. This is particularly useful when a supplement is stimulant-heavy as the positive effects are promoted while the negatives are reduced. Anyone using nootropics – smart drugs – will appreciate the high levels of concentration and lack of jitters.
1. Haaz S et al – Citrus aurantium and synephrine alkaloids in the treatment of overweight and obesity – 2006
2. Marchei E et al – A rapid and simple procedure for the determination of synephrine in dietary supplements by gas chromatography-mass spectrometry – 2006
3. Stohs SJ et al – Effects of p-synephrine alone and in combination with selected bioflavonoids on resting metabolism, blood pressure, heart rate and self-reported mood changes – 2011
4. Bui LT et al – Blood pressure and heart rate effects following a single dose of bitter orange – 2005
5. Sale C et al – Metabolic and physiological effects of ingesting extracts of bitter orange, green tea and guarana at rest and during treadmill walking in overweight males – 2006
6. Haller CA et al – Hemodynamic effects of ephedra-free weight-loss supplements in humans – 2005