Skin Cancer Prevention
The flavonoids in an orange peel help vitamin C, an important antioxidant vitamin, work more efficiently. Flavonoids also retard the growth of cancer cells by withholding energy requirements needed by these harmful cells. In a 2000 study conducted at the Arizona Cancer Center, researchers found that d-limonene, a major component in orange peels, reduced the occurrence of squamous cell carcinoma, a deadly form of skin cancer. Participants who regularly consumed the peel of an orange had a significantly reduced rate of skin cancer over those who regularly consumed only the orange.

Inhibits Cancer of the Lung
Two compounds in orange peel may protect against cancer of the lung. A 2009 study conducted at the Department of Foods Science at the University of Massachusetts found polymethoxyflavones contained in the peel of sweet oranges inhibited the growth of cancer cells of the lung. Another compound, called liminoid, might also be responsible for preventing cancer of the lung as well as cancer of the stomach, colon and breast.

Lowers Cholesterol
An orange peel contains two important flavones: hesperidin and polymethoxylate. These are compounds that help lower low-density lipoprotein, or LDL, cholesterol, according to a 2004 joint study conducted by the U.S. Department of Agriculture and KGK Synergize, a nutraceutical company. Researchers suggest that taking dietary supplements containing orange is more ideal than eating the peels. The reason: you would need to eat 20 orange or tangerine peels a day for the peels to have a therapeutic effect on LDL cholesterol .

Help With Smoking
Orange peel extract is an ingredient used in a variety of beauty and health products, ranging from cold medicines to bath and body products. One notable product has shown to help with quiting smoking. According to Medical News Today, a scientifically proven that nicotine gum, with dried orange peel as one of the ingredients, helps break down and remove nicotine from the body. The gum, which was developed by a Korean scientist and professor, Hyun-Won Kim, of the University of Yonsei's College of Medicine, is particularly helpful for those who are in the contemplation stage of stopping -- or those who aren't quite ready to quit yet. - Millet

Great to know, thanks for the info.

Very interesting. How do you eat an orange peel like for the first study ? Can you consume enough to do any good in a tablet or capsule ? Tom

I don't know many who just eat straight orange peel, but consuming marmalade with peel, kumquats & zest probably would be most common way go getting the benefits of the peel I would think.

Also I personally would be concerned what effect pesticides/ fungicides, found on commercially grown orange peel would have on me if i ate it. Another benefit of home grown citrus!

Ryan, good point. If one eats the peel of a commercial citrus fruit (or any variety of a commercial frut), it would be a good idea to first wash it. I had at one time a department head that ate an orange the same way that most people eat an apple. He would bite into an unpeeled orange and eat the entire fruit. - Millet

Citrus fruit are washed & waxed before being shipped to the stores. As long as you enjoy the wax or can find a way to remove it.

Very interesting information, Millet. I tried to verify the information regarding the cholesterol lowering claims. Looks to me like the nutraceutical company conducted that "research", so not so sure how accurate the findings are. I will have to see if I can find the actual study. And, reasoning is because it does seem that you might have to eat an awful lot of peel in order to see results. But, if this is the case, it sure would be great news. I would love to see more research around citrus and its health benefits. The frustrating part is there simply isn't the "big bucks" behind the research, as big pharma can't really benefit from producing medicines from citrus. It is very hard to patent those products (nutraceuticals). So research dollars are in short supply. I hope to hear more about these findings.

That's good to know, I'm smoker! Millet thanks for sharing these info's!

Here the problem is that the stores citrus fruits are not just waxed are also treated with systemic fungicide which contains active substances like imazalil and prochloraz. Sometimes the fungicide is also mixed with orthophenyl phenol (E 231) and/or tiabendazole (E233). This is specified on the label ‘The zest(rind) is unusable for eating’.

Here really worth to home grown citrus!

From USDA Research
Can Citrus Help Your Health

These days, juicy, delicious oranges are practically synonymous with vitamin C. But did you know that America's favorite fruit also provides healthful natural compounds called limonoids? In laboratory tests with animals and with human cells, citrus limonoids have been shown to help fight cancers of the mouth, skin, lung, breast, stomach, and colon.


Now, ARS scientists in northern California—led by chemist Gary D. Manners of the Western Regional Research Center in Albany—have uncovered new details about these compounds. Their research has demonstrated that our bodies can readily access a limonoid called limonin, and all its health-imparting properties, each time we bite into a citrus slice or drink a glass of orange juice, for instance. This is the first time this bioavailability has been shown in humans.


"Limonin is what remains after our bodies cleave a glucose, or sugar molecule, from limonin's parent compound, limonin glucoside," says Manners. "Limonin glucoside is present in citrus and citrus juices in about the same amount as vitamin C."

, their positive impact on our health is becoming clearer with every experiment.


In some individuals, limonin remains in the bloodstream for up to 24 hours—an impressive length of time—Manners and colleagues found. This longevity, or persistence, may help explain some limonoids' ability to fight cancer cells, which, if not continuously suppressed, may proliferate.


The findings are good news for people who like oranges and the other appetizing citrus fruits rich in limonoids. The world's citrus-juice processors could also benefit; they could extract an estimated 300,000 pounds of these chemicals from peels, seeds, and other processing leftovers each year.


Today, those leftovers, called citrus molasses, are sold as a low-cost ingredient in cattle feed. But thanks to a patented, ARS-developed process, these chemicals can be extracted from citrus molasses and used to fortify foods or beverages.

Test Targets Limonin Glucoside


For the bioavailability experiment, 16 healthy men and women volunteers downed a dose of pure limonin glucoside. The compound, a white, tasteless, odorless powder, was dissolved in about 4 ounces of water. Doses ranged from about one-eighth to one teaspoon. That's equal to the amount in seven glasses of orange juice.


The participants gave blood samples before they drank the beverage and 3, 6, 12, and 24 hours afterwards. To avoid skewing test results, they didn't eat or drink any citrus products for 3 days before and 3 days after taking part in the study.


The scientists looked for traces of limonin—the limonin glucoside byproduct or metabolite—in the volunteers' blood plasma. The laboratory procedure that the researchers used, liquid chromatography-mass spectrometry, can detect very small amounts of limonin.


Limonin showed up in the plasma of all volunteers except one. For most volunteers, the concentration was highest within 6 hours after they drank the special beverage. Five volunteers still had traces of limonin after 24 hours. That's an indication of the compound's staying power, an important consideration, especially if limonin glucoside were to be used as a pharmaceutical, for example.


In contrast, some natural compounds are bioavailable for shorter periods and have to be taken more than just once a day. An example: the good-for-you phenols in green tea last only 4 to 6 hours.


In this study, Manners collaborated with Andrew P. Breksa III of the Western Regional Research Center; Thomas S. Schooch, formerly of the center; retired ARS chemist Shin Hasegawa, a pioneering investigator of these citrus biochemicals; and Robert A. Jacob, formerly a chemist with the ARS Western Human Nutrition Research Center in Davis, California, and now retired. The group published their findings in a 2003 issue of the Journal of Agricultural and Food Chemistry. The Florida Department of Citrus helped fund the work.

CAN LIMONIN LOWER CHOLESTEROL?

There's more to come from the California team. Manners and Breksa, along with chemist Darshan S. Kelley and molecular biologist Susan J. Zunino—both of the Davis nutrition center—are gearing up for a first-of-its-kind study of the cholesterol-lowering effects of limonin.


In 2000, Manners, Hasegawa, and their Canadian co-authors reported that limonin may be among the citrus-juice compounds that lower cholesterol. In lab tests, they found that human liver cells produced less apo B—a compound associated with higher cholesterol levels—when exposed to limonin.


Preliminary results of the new cholesterol study are expected later this year. This investigation may provide more details about the health advantages of citrus and greater incentive for us to enjoy these sunny, delectable fruits and juices even more often

Millet

This is the most fantastic research on citrus. Millet, can you provide the link to this article? This would make me go back to grad school to get my PhD. This is just absolutely fascinating. Isn't limonin the bitter chemical that forms with Navel orange juice when it's refrigerated?

My understanding is that limonin is the chemical responsible for the bitterness in juice of navel oranges, a compound that is the precursor to limonin which is not bitter exists in the orange, it is not until the juice sacs are broken during juicing that the conversion to limonin begins, the precursor compound is known as LARL.

Patty, sorry I did not supply the link on the above research. Here it is:
http://www.ars.usda.gov/is/ar/archive/feb05/citrus0205.htm?pf=1

Millet

Thank you, Millet. A little light reading for the evening!

Yay! More chocolate-covered candied orange peels!