Bitter Orange for Weight Control

Some dieters say that bitter orange helps increase calorie burning and suppress appetite.

Bitter orange (Citrus aurantium) contains several substances known to stimulate metabolic rate, which should increase calorie burning. While no published research has tested it alone, it appears to be effective in combination with St. John’s wort and caffeine.

Although historically used to stimulate appetite, bitter orange is frequently found in modern weight-loss formulas because synephrine is similar to the compound ephedrine, which is known to promote weight loss. In one study of 23 overweight adults, participants taking a daily intake of bitter orange (975 mg) combined with caffeine (525 mg) and St. John’s wort (Hypericum perforatum, 900 mg) for six weeks lost significantly more body weight and fat than the control group.¹ No adverse effects on heart rate or blood pressure were found. Bitter orange standardized to contain 4 to 6% synephrine had an anti-obesity effect in rats. However, the amount used to achieve this effect was accompanied by cardiovascular toxicity and mortality.²

Bitter orange oil may possibly cause light sensitivity (photosensitivity), especially in fair-skinned individuals.³ Generally this occurs only if the oil is applied directly to the skin and then exposed to bright light; in rare cases it has also been known to occur in people who have taken bitter orange internally. The oil should not be applied topically and anyone who uses it internally should avoid bright light, including tanning booths.

Internal use of the volatile oil of bitter orange is also potentially unsafe and should not be undertaken without expert guidance. Large amounts of orange peel have caused intestinal colic, convulsions, and death in children.⁴ The amounts recommended above for internal use should not be exceeded.

One text on Chinese medicine cautions against the use of bitter orange in pregnancy.⁵ This concern is not raised in any other reference, and the American Herbal Products Association classifies the herb as "class 1," an herb that can be safely consumed during pregnancy when used appropriately.⁶

Decoctions of bitter orange substantially increased blood levels of cyclosporine in pigs, causing toxicity.⁷ Bitter orange also inhibited human cytochrome P450 3A (CYP3A) in the test tube.⁸ This is an enzyme that helps the liver get rid of numerous toxins, and strongly affects metabolism of certain drugs. Bitter orange might, therefore, interact with drugs that are metabolized by CYP3A. To be on the safe side, bitter orange should not be combined with prescription medications, unless someone is under the care of an experienced natural medicine clinician.