Synephrine is a substance obtained from the fruits of bitter orange with the properties dangerously resembling ephedrine and amphetamine. It belongs to the so-called thermogenics accelerating weight loss. The application of supplements with synephrine may entail side-effects, which are dangerous to health.

The source of synephrine – bitter oranges

The variety of applications of bitter orange fruits may be surprising. Although freshly picked from a tree they are not suitable to eat (due to bitter taste), the preserves made of them are famous in the food industry. Starting from marmalades and confitures to alcohols – famous blue liquor Curaçao is made of bitter oranges. Apart from this, fruit covers fried with sugar are used to ornament cakes and orange oil obtained from them are used as the essence of cakes and sweet meals. Dried skin of bitter orange is used in traditional Chinese medicine to stimulate appetite and treat indigestion. In this context, it almost paradoxically seems that it finds application in dietary supplements supporting weight loss. It happens thanks to synephrine – an alkaloid, which constitutes ca. 6% of the extract from bitter orange fruit.

Synephrine increases thermogenesis

The problem of every person that decides to lose weight is the excess of fatty tissue. It is most often located on the belly, hips and buttocks in the form of “folds”, which are an unaesthetic nightmare of each woman. The fight with unwanted fat is not easy and requires considerable physical effort and liters of sweat. Intensive training causes the acceleration of metabolism, the increase of body temperature and burning fat, which in such a situation is the source of energy for the organism. What if we don’t like sweating or don’t have the time to go to the gym?

In such situations one may reach for the so-called thermogenics. This name is used for natural substances, which cause the release of fat from the organism by increasing metabolism, energy expenditure and acceleration of fat burning. They constitute a separate segment of dietary supplements, which support weight loss. They are very popular, especially among bodybuilders, as by minimizing the size of fatty tissue, they help to better expose muscles.

Unfortunately, forbidden or dangerous substances often are used as thermogenics, which at the same time are considered the most effective. It is for example dinitrophenol (DNP), the application of which caused a few deaths in Europe. Ephedrine is also a strong thermogenic (amphetamine’s precursor), which a few years ago constituted a frequent additive to supplements for weight loss. Unfortunately, during long application of this kind of drugs, a range of side-effects appeared and even the cases of deaths. For this reason Food and Drug Administration in the USA banned the use of ephedrine in slimming preparations on the 12th of April 2004. In Poland, ephedrine is sold on prescription, mainly in drugs constricting nose mucosa.

Synephrine – a safer substitute of ephedrine?

For years people have been looking for substances, which could replace ephedrine in the preparations for weight loss. Substances, that would be similar in effectiveness and at the same time safer for health and life of the users. In this way, synephrine was found, the chemical structure of which is very close to ephedrine. Similarly to its effect. Synephrine stimulates the nervous system like adrenaline, tyramine or ephedrine. It influences beta-3 receptor, due to which it causes lipolysis (the breakdown of fats) with the simultaneous activation of thermogenesis. Synephrine also increases blood pressure, accelerates blood circulation and increases heart minute volume. At the same time it widens bronchial tubes, stops the attacks of asthma and decongests sinuses, similarly to ephedrine.

Synephrine – undesirable effects

Along with the appearance of the preparations with synephrine on the market, some reports appeared, indicating that similarly to ephedrine, they may constitute danger to health. In literature we may also find a range of reports regarding negative effects of using preparations free from ephedrine, but containing synephrine. In one of the studies, the researches proved that the application of 900 mg of the extract standardized for the content of 6% of synephrine in the form of a dietary supplement may cause the increase of blood pressure and heart action after a few hours from taking a single dose. There is also a well-known case of 55-year-old woman, who was diagnosed with heart attack and who during the preceding year had been taking a slimming preparation containing 300 mg of bitter orange.

Therefore, is synephrine safe? According to the European Food Safety Authority (EFSA), a given substance may be considered safe, if it has been used for a large population for many years and no harmful symptoms have been observed and the size of its application remains unchanged. In case of bitter orange fruit, which is the source of synephrine, these conditions are not entirely fulfilled, as the size of use in recent years has been definitely increased. The intended use of products containing synephrine has also changed.

Supplements with synephrine – from the Internet or from the pharmacy?

So far, the application of synephrine and bitter orange fruit extracts in dietary supplement has been legal and widely used. In the pharmacies in Poland we may also find a few preparations with synephrine. However, much more supplements containing synephrine are available in various Internet shops. It is worth taking caution in these cases. The recently published report of the Supreme Chamber of Control indicated that dietary supplements supporting weight loss, which are available only on the Internet, most often demonstrate contradictions as for the real composition of the product and the declaration of the producer. They are very frequently falsified by adding illegal and dangerous substances. In this context, the preparations available in pharmacies (especially from producers using increased standards of production) seem a safer solution.

What is a safe dose of synephrine?

According to the Institute of Risk Evaluation in Berlin, average intake of synephrine with diet does not exceed 6,7 mg. Only people who use exceptionally high doses of citruses, orange juices or citrus jams may reach 25,7 mg a day. It is assumed that it is dangerous to exceed 27 mg of synephrine a day. The majority of the preparations available in pharmacies contain the extract from bitter orange fruit standardized for the content of 6% of synephrine – this piece of information is important, as producers of the supplements containing this extract do not provide the content of synephrine.


Synephrine is especially dangerous in combination with caffeine, which may be found in coffee or cola and with energizers. An example of this may be the case of 27-year-old German woman, who daily took 100 mg of this substance along with 400 mg of caffeine. After two weeks during fitness activities her heart stopped. The preparations with synephrine or bitter fruit extracts should not be used by people taking any drugs – especially antidepressants. Available sources describe the case of 52-year old woman taking thyroxine who suffered from tachycardia after the application of a dry extract from unripe fruits of bitter orange (500 mg of extract containing 30 mg of synephrine). In the opinion of authors of these revelations it should be highlighted that this kind of preparations may interact with antidepressants, thyroxine or drugs for cardiovascular diseases.

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