By 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.
… Taken all together, a considerable number of well-established lines of evidence have confirmed that flavonoids in citrus peel exhibit a remarkable spectrum of efficacious biological activities, particularly in antitumorigenesis.
Excellent permeability through membrane allows citrus flavonoids to possess great bioavailability, which consequently attracts researchers to perform scientific studies for effective disease prevention and treatment."
Orange Peels Offer Anti-Allergic and Anti-Inflammatory Benefits
Compounds in orange peels and other citrus peel may prevent histamine release (histamines are the chemicals that cause allergic reactions), making them a potentially anti-allergic food.8
The peels may also help to cleanse your lungs, helping you to expel phlegm, and the high levels of vitamin C are beneficial for your immune system, which may help you fight off respiratory illnesses like colds and flu.
In addition, citrus peel extract helps suppress inflammation similar to the anti-inflammatory drug indomethacin.9 The peel may offer a range of additional health benefits as well, including:10
- Improve digestion and speed metabolism, according to the principles of Ayurveda
- Improve oral health: chew orange peels as a natural breath freshener or rub the inside on your teeth to help with whitening and sensitivity
- Improve skin appearance: Rub orange peel extract combined with milk to help lighten dark spots on your skin or use it as a skin toner
- Support healthy weight loss: Orange peels are low in calories and high in fiber, making them a useful food if you're trying to lose weight.
Other Fruit Peels and Rinds Can Be Healthy Too
The rinds, peels, stems, leaves and seeds and many fruits and vegetables can be safely consumed and often contribute valuable nutrition and phytochemicals to your diet. So there's no need to limit yourself to orange peels. For instance:11
- Swiss chard stems are rich in the amino acid glutamine, which is beneficial for your immune system.
- Celery tops contain five times more magnesium and calcium than the stalks.
- Broccoli leaves provide about 90 percent of your daily vitamin A requirement, compared to 3 percent in the florets.
- Onion skins: The outer layers of the onion (including the papery skin) are thought to be the most nutritious, including concentrating the highest amounts of flavonoids.12 Try simmering onion skins in soups and stock then removing before serving.
Watermelon rinds and seeds are another example. Watermelon rind contains more of the amino acid citrulline than the pink flesh.13 Citrulline is converted to arginine in your kidneys, and this amino acid is important for heart health and maintaining your immune system.
Black watermelon seeds are also edible and actually quite healthy. They contain iron, zinc, protein and fiber. Passion fruit peel provides another example.
It contains a novel mixture of bioflavonoids that have been found to reduce wheeze and cough and improve shortness of breath in people with asthma.14
Delicious Ways to Incorporate Citrus Peels into Your Diet
If you'll be consuming citrus peels, be sure to choose organic fruits only. Oranges, lemons and limes topped the list of foods that most commonly contain more than one pesticide residue in the U.K.,15 and these will be concentrated on the outer peel.
The fruit should be washed well (even if it's organic) prior to use. Then, one of the easiest ways to eat orange peels is to grate the zest and add it to salads, dressings, yogurt, tea, fish and vegetables.
You can also blend the peel and pith into smoothies (in the case of watermelon rind, try it blended up with lime juice for a refreshing treat). Lemon peel and pith provide many similar benefits to orange peel.
If you'd like to try it in a new way, here's a recipe for Moroccan preserved lemons posted by Epicurious.16 When they're ready, the peel can be added to many dishes, such as chicken salad, stews and vegetable dishes.
Moroccan-Style Preserved Lemons17
Cooks' note: Preserved lemons can be chilled, covered in their juices, up to one year.