Synephrine: what is it and why is it in fat burners

Synephrine is an alkaloid from the unripe fruit of the bitter orange (Citrus aurantium), structurally related to ephedrine, but with a significantly weaker effect on the body. It appeared in supplements in large quantities after 2004, when ephedrine was withdrawn from the dietary supplement market due to safety concerns.

Why is there no "new ephedrine"?

Both substances are sympathomimetics — they act on the sympathetic nervous system. However, they differ in which receptors and how strongly. Ephedrine acted significantly on beta-1 receptors in the heart, which meant a noticeable effect on heart rate and blood pressure, and this is what led to its withdrawal. Synephrine has a significantly lower affinity for these receptors, and therefore its effect on the circulatory system is smaller at normal doses.

But a weaker effect on the heart also means a weaker effect overall. Anyone expecting synephrine to do what ephedrine did will be disappointed — and that's a good thing.

What can we say about him?

Nothing. European legislation does not allow any health claims for synephrine, so no manufacturer in the EU is allowed to write on the packaging or website that it supports weight loss, fat burning, or anything similar. If you see this written somewhere, it is a violation of Regulation (EC) No. 1924/2006 — and it is worth asking what else does not fit on the packaging.

What to watch out for

• Combination with a high dose of caffeine. The effects are additive; this is why both substances appear together in products, and also a reason to monitor your total daily caffeine intake.
• High blood pressure and heart disease. If you have these conditions, avoid stimulants or consult your doctor first.
• Sports testing. Synephrine is not on the WADA banned substances list, but is in the monitoring program. If you compete under anti-doping rules, check your current status.
• Interactions: Caution is advised with MAOI antidepressants and blood pressure medications.

How to summarize

Synephrine is a legal, well-tolerated ingredient that adds a mild stimulant to the mix at normal doses. It is not a miracle drug and should not be marketed as such. It is one of two substances that differentiates the stronger version of ADI-PEX® from the milder version — and the reason we recommend starting with the milder version.