We’re all familiar with sweet oranges, the kind you peel and eat. But there are also bitter oranges (Citrus aurantium), including Seville, Bergamot and other varieties. Too sour to eat on their own, these large, deeply colored oranges are typically used in marmalades, chutneys and candied fruits (their high pectin content helps the gelling process) and as a flavoring for other foods and beverages. Bitter orange extract became popular as a weight-loss supplement after the Food and Drug Administration (FDA) banned the herb ephedra due to safety issues.
A supplement to avoid?
Bitter orange has a long history of medicinal use in China and the Amazon rainforest—for treating nasal congestion, heartburn, indigestion, bladder problems, insomnia and other maladies. Paradoxically, it’s claimed to reduce fatigue and increase relaxation, relieve constipation yet act as a laxative, and help in both weight loss and loss of appetite. The German Commission E recognizes bitter orange peel as a remedy for upset stomach and appetite loss, but there’s little, if any, evidence to support most other uses. Lab studies suggest that compounds in bitter orange may have anti-cancer properties.
Extracts of the dried immature fruit and peel of bitter orange, used in diet supplements, contain synephrine and octopamine, alkaloids that act on the sympathetic nervous system and have stimulant effects. Chemically related to ephedrine (in ephedra), these compounds increase calorie burning in the short term, but there’s concern that they may, like ephedra, increase heart rate and blood pressure and possibly worsen existing heart problems.
Consumer Reports recently listed bitter orange as one of 12 supplements to avoid because it has been linked to—though not proven to cause—a range of problems, including fainting, heart attacks, angina, strokes and even death. According to Health Canada, which functions like the FDA, “there is insufficient information to establish the safety or long-term use of synephrine-containing products.”
On the other hand, some researchers say that the physiological effects of bitter orange may be different from and milder than ephedra. Adverse effects reported from supplements may have been due, at least in part, to other ingredients or risk factors in people taking them. Combining bitter orange with caffeine or other stimulants, or with drugs that increase blood pressure, may increase the risks.
In any case, there’s no evidence that the supplements have a significant effect on body fat or weight. A study published in Obesity Research in 2005 found that bitter orange increases calorie burning, but estimated that this would result in a weight loss of only 2.2 pounds, on average, over six months. Other studies have had unclear or inconsistent results. Moreover, different formulas have varying levels of synephrine and thus can differ in their effects.
As with grapefruit, bitter orange inhibits an enzyme in the small intestine, and this can affect the blood levels of many medications, including some calcium channel blockers, statins, antiviral drugs, antidepressants and anti-anxiety drugs.
Though it’s hard to consume large amounts of bitter orange juice, there’s also some concern that it, like the supplements, may have adverse heart effects. No change in heart rate or blood pressure was seen in a small study in the Journal of Clinical Pharmacology of healthy young people who drank 8 ounces of juice. However, the researchers advised anyone who has uncontrolled high blood pressure, heart rhythm abnormalities or narrow-angle glaucoma or who takes decongestants or certain antidepressants (MAO inhibitors) to avoid the juice.