Bitter orange is being marketed as a natural weight-loss product. In several small clinical studies, subjects have been shown to have increased metabolic rates when taking bitter orange. However, it has yet to be confirmed that bitter orange is beneficial for weight loss. In addition, bitter orange contains two chemicals (synephrine and octopamine) that are similar in structure to those found in ephedra, a herbal stimulant banned by the FDA. Synephrine has been demonstrated to increase blood pressure and increase the risk of adverse cardiovascular events. According to the National Center for Complementary and Alternative Medicine, there have been reported cases of healthy people fainting, and experiencing heart attacks and strokes, after taking bitter orange alone or in combination with caffeine.

What is bitter orange?

Bitter orange, also known as Seville orange and marmalade orange, comes from the fruit of a citrus tree (Citrus aurantium). Bitter orange is used in herbal medicine as a stimulant and appetite suppressant. After the U.S. Food and Drug Administration (FDA) banned the herbal stimulant ephedra, manufacturers substituted bitter orange in its place in many herbal weight-loss products. The National Center for Complementary and Alternative Medicine has stated that there is not enough scientific evidence to support the use of bitter orange for health purposes. Indeed, no studies have shown that the herb is useful in treatment of nausea, indigestion, constipation, heartburn, nasal congestion or fungal infections.

Side effects of bitter orange

Bitter orange can cause abnormal heart rhythms, elevate blood pressure and speed up heart rate. It should only be used under the direction of a physician. Individuals with a cardiovascular condition such as heart disease and high blood pressure, or diabetes, should not take bitter orange. According to the National Center for Complementary and Alternative Medicine, there have been reports of fainting, heart attack and stroke in healthy people after taking bitter orange alone or with caffeine. Bitter orange should not be consumed with caffeine containing substances such as green tea and yerba mate – found in many diet pills. It should also be avoided by anyone taking medications (such as MAO inhibitors) or herbs/ supplements that increase heart rate. Pregnant women should avoid products that contain bitter orange.

Is bitter orange effective?

Some studies suggest that bitter orange can promote modest weight loss when combined with diet and exercise. Synephrine has lipolytic effects in human fat cells only at high doses, and octopamine does not have lipolytic effects in human adipocytes.

Bitter orange constituents

Bitter orange contains synephrine (oxedrine), which is structurally similar to epinephrine. Synephrine increases blood pressure and has the potential to increase cardiovascular events. Additionally, bitter orange contains 6′,7′-dihydroxybergamottin and bergapten, both of which inhibit cytochrome P450-3A, and thus could increase serum levels of many drugs.