From Dr. Mercola:
Oranges are one of the most popular fruits in the U.S., but very few consume the peel, which is arguably the healthiest part of the whole fruit. Orange peels are rich in flavonoids, like hesperidin and polymethoxyflavones (PMFs), and other phytochemicals, which contribute many of their health benefits.
Flavonoids — antioxidant compounds found in certain fruits, vegetables, herbs, and spices — are known for their role in helping to prevent chronic diseases like heart disease and cancer.
In addition, orange peel contains higher amounts of certain nutrients than its flesh. For instance, 3.5 ounces of orange peel provides 136 milligrams (mg) of vitamin C, while the flesh contains about 71 mg.1
Orange peel also contains considerable amounts of calcium, copper, magnesium, vitamin A, folate and other B vitamins and dietary fiber.
They have an intense orange and bitter flavor, but the latter is often a clue that a food is healthy; the bitter taste is the result of the many flavonoids that orange peels contain.
Orange Peels for Heart Health
Orange peels (as well as the underlying white pulp, or pith) are rich in hesperidin, a flavonoid that’s been shown to lower high blood pressure and cholesterol in animal studies. It also has anti-inflammatory properties.2
In middle-aged, overweight men, consuming hesperidin in oranges was found to significantly lower diastolic blood pressure (DBP) after four weeks.3
The polymethoxylated flavones (PMFs) in orange peels have also been shown to lower cholesterol more effectively than prescription drugs, without the side effects.4
The study’s lead author, Elzbieta Kurowska, Ph.D., vice president of research at KGK Synergize in Ontario, Canada, told EurekAlert:5
“Our study has shown that PMFs have the most potent cholesterol-lowering effect of any other citrus flavonoid We believe that PMFs have the potential to rival and even beat the cholesterol-lowering effect of some prescription drugs, without the risk of side effects.”
Orange Peels May Have Anti-Cancer Activity
The flavonoids in orange peel have the potential to inhibit the RLIP76 protein, which is linked to cancer and obesity. Research is in the early stages, but if an orange peel extract could inhibit or reduce expression of RLIP76, it would have significant implications for chronic disease.
“When you get rid of this [RLIP76] gene in a mouse, it would appear that the mouse can’t get obese, it can’t get diabetes, it can’t get high cholesterol and it can’t get cancer,” said Sanjay Awasthi, M.D., professor in the Division of Molecular Diabetes Research at City of Hope hospital.6
Flavonoids in orange and other citrus peels exert a number of additional anti-cancer effects as well. According to research published in the journal BioMed Research International:7
“Due to their broad range of pharmacological properties, citrus flavonoids have gained increased attention. Accumulative in vitro and in vivo studies indicate protective effects of polymethoxyflavones (PMFs) against the occurrence of cancer.
PMFs inhibit carcinogenesis by mechanisms like blocking the metastasis cascade, inhibition of cancer cell mobility in circulatory systems, proapoptosis, and antiangiogenesis.