Bitter orange supplementation is dangerous and unlikely to work.

Common Names:  Bitter orange, Seville orange, sour orange, bigarade orange, zhi shi, or marmalade orange.  

often added in place of ephedra in the “ephedra-free” products.  The tree and its fruit are native to southeast Asia, and the trees have been spread by humans to many parts of the world.  Wild trees are found in wooded parts of Florida and The Bahamas.  The trees were spread to the Americas by the Spanish. 

The tree and its fruit have many uses to include English marmalade, essential oils in perfumes, solvents, and herbal supplements.   Bitter orange is also employed in herbal medicine as a stimulant and appetite suppressant, due to its active ingredient, synephrine.  Bitter orange supplements have been linked to a number of serious side effects and deaths, and consumer groups advocate that people avoid using the fruit medically.

History:

• Bitter orange has been used in traditional Chinese medicine and by indigenous people of the Amazon rainforest for constipation. Amazonian natives also used it for nausea and indigestion.
• Today, people use various bitter orange products as a dietary supplement for heartburn, loss of appetite, nasal congestion, and weight loss. It is also applied to the skin for pain, bruises, and bed sores.
• Bitter orange oil has been used for decades for jock itch and has been show to be effective.  

How does it work for weight loss?  Synephrine is known to be an endogenous metabolite of octopamine metabolism.   Synephrine appears to be an endogenously produced end product of tyramine metabolism.   Tyramine and synephrine are similar in effect to adrenalin or epinephrine.  Synephrine is an active metabolism booster that increases energy expenditure, heart rate, and blood pressure.  

Blood pressure: A single dose of 50mg p-synephrine, when taken by healthy subjects in a rested state over the course of 75 minutes, does not appear to significantly influence blood pressure nor heart rate​[1]​.  Higher does increase blood pressure and the effect on blood pressure is high on individuals that are more sensitive to the effects of the supplements.  Another study was done with a 900 mg pill of a supplement that contained 6% synephrine which resulted in elevations in blood pressure and heart rate for up to 5 hours after taking the supplement​[2]​.  

2. Metabolism:  A single dose of 50mg p-synephrine, when measured over the next 75 minutes in otherwise healthy subjects in a rested state, has been noted to increase by just under 80 calories to subjects BMR[3].

3. Hunger: Most of the research has shown that synephrine has little no effect on appetite[4].  

4. Weight Loss:  The most comprehensive study analysed all existing research on this supplement and demonstrated no statistically significant benefit for weight loss[5].  The problem is that it had a small number involved in the study.  It also showed information about safety either.

5. Unsafe: Although there are number studies that are conflicting, there are a number case reports that show adverse outcomes.  One case in a 24-year-old male showed a tie between the supplement and a special type of myocardial infaction[6].  Another case report showed a tie between the supplement and stroke[7].

The bottom line: The supplement should increase your metabolism based on the chemical family for which it belongs, btu the research does not pan out in the research.  For this reason and the adverse events that have been reported, I highly recommend that you avoid this supplement.  The National Collegiate Athletic Association has placed synephrine and thus bitter orange on its current list of banned drugs.  That should be enough for you to doubt its safety.  Besides this, bitter orange has little evidence to support its role as a weight-loss supplement, and the only research to claim this was privately funded therefore had compounding interests.  I consider this supplement unsafe.