Oranges

Health benefits

Oranges’ healing phytonutrients

Oranges contain a broad spectrum of phytonutrient compounds: citrus flavanones (including hesperetin and naringenin), anthocyanins, hydroxycinnamic acids, and other polyphenols. These compounds work alongside the fruit’s vitamin C to produce measurable antioxidant activity.

One flavanone in particular, hesperidin, has received concentrated research attention. In animal studies, hesperidin lowered blood pressure and cholesterol levels while reducing markers of inflammation. Most of this compound concentrates in the peel and inner white pith rather than the juice. Commercial juicing strips away the pith, removing the primary source of hesperidin from the finished product.

Vitamin C concentration and antioxidant function

One medium orange (131g) provides 69.7 mg of vitamin C, covering 93% of the Daily Value. Vitamin C is the primary water-soluble antioxidant in the body, neutralizing free radicals in aqueous environments both inside and outside cells. Within cells, free radical damage to DNA can initiate carcinogenesis. In tissues with rapid cell turnover, such as the colonic epithelium, preventing DNA mutations is especially relevant. Epidemiological data links adequate vitamin C intake to reduced colon cancer risk.

Free radical damage to other cellular structures and other molecules can result in painful inflammation, as the body tries to clear out the damaged parts. Vitamin C, which prevents the free radical damage that triggers the inflammatory cascade, is thus also associated with reduced severity of inflammatory conditions, such as asthma, osteoarthritis, and rheumatoid arthritis.

Free radicals also oxidize cholesterol. Only after being oxidized does cholesterol stick to the artery walls, building up in plaques that may eventually grow large enough to impede or fully block blood flow, or rupture to cause a heart attack or stroke. Since vitamin C can neutralize free radicals, it can help prevent the oxidation of cholesterol.

Vitamin C also supports immune function by enhancing neutrophil chemotaxis and phagocytic capacity.

A glass of orange juice more protective than vitamin C alone

Consuming vitamin C supplements does not provide the same protective benefits as drinking a glass of orange juice, shows research by Italian researchers in the Division of Human Nutrition at the University of Milan, Italy (Guarnieri S, Riso P, et al., British Journal of Nutrition).

Seven healthy test subjects were given each of three drinks, two weeks apart: blood-orange juice containing 150 milligrams of vitamin C, fortified water containing 150 milligrams of vitamin C, and a sugar and water solution containing no vitamin C. Blood samples were collected immediately before the drink was consumed, then every hour for 8 hours, and finally 24 hours after consumption of each drink.

Blood samples were exposed to hydrogen peroxide, and free radical damage to DNA was evaluated at 3 and 24 hours. Only when orange juice was consumed was any protective effect seen. After drinking orange juice, DNA damage was 18% less after 3 hours, and 16% less after 24 hours. No protection against DNA damage was seen after consumption of the vitamin C fortified drink or the sugar drink.

While another study, which looked at much larger quantities of vitamin C, did show a protective effect from the vitamin alone, this research indicates that not only is the protection afforded by fruit more complex, but smaller amounts of nutrients like vitamin C are all that are needed for benefit.

Lead researcher Serena Guarnieri noted, “It appears that vitamin C is not the only chemical responsible for antioxidant protection.” In oranges, vitamin C exists within a matrix of cyanidin-3-glucoside, flavanones, and carotenoids. The precise interactions between these compounds remain under investigation, but the practical takeaway is straightforward: whole orange juice outperforms isolated vitamin C for DNA protection.

Epidemiological data consistently associates higher intake of vitamin C-containing fruits and vegetables with reduced all-cause mortality, including death from cardiovascular disease, stroke, and cancer.

Orange’s potential protection against cardiovascular disease

A 248-page report, “The Health Benefits of Citrus Fruits,” released December 2003 by Australian research group, CSIRO (The Commonwealth Scientific and Industrial Research), reviews 48 studies that show a diet high in citrus fruit provides a statistically significant protective effect against some types of cancer, plus another 21 studies showing a non-significant trend towards protection.

Citrus appeared to confer the strongest protection against esophageal, oropharyngeal/laryngeal, and stomach cancers, with risk reductions of 40-50% in the reviewed studies.

The World Health Organization’s draft report, “Diet, Nutrition and the Prevention of Chronic Disease,” concluded that citrus fruits protect against cardiovascular disease through multiple mechanisms: folate lowers homocysteine (a cardiovascular risk factor); potassium reduces blood pressure and protects against stroke and cardiac arrhythmias; and vitamin C, carotenoids, and flavonoids each contribute measurable cardiovascular protective effects.

One large US study reviewed in the CSIRO report showed that one extra serving of fruit and vegetables a day reduced the risk of stroke by 4%, and this increased by 5-6 times for citrus fruits, reaching a 19% reduction of risk for stroke from consuming one extra serving of citrus fruit a day.

The CSIRO Report also includes evidence of positive effects associated with citrus consumption in studies for arthritis, asthma, Alzheimer’s disease and cognitive impairment, Parkinson’s disease, macular degeneration, diabetes, gallstones, multiple sclerosis, cholera, gingivitis, optimal lung function, cataracts, ulcerative colitis and Crohn’s disease.

Finally, the CSIRO Report notes that as low fat, nutrient-rich foods with a low glycemic index, citrus fruits are protective against overweight and obesity, conditions which increase the risk of heart disease, certain cancers, diabetes, high blood pressure and stroke, and add to symptoms of other conditions like arthritis.

An orange has over 170 different phytonutrients and more than 60 flavonoids, many of which have been shown to have anti-inflammatory, anti-tumour and blood clot inhibiting properties, as well as strong antioxidant effects.

Oranges contain approximately 84 mg gallic acid equivalents per 100 mg of polyphenol content. These polyphenols demonstrate antioxidant, anti-viral, anti-allergenic, anti-inflammatory, anti-proliferative, and anti-carcinogenic activity in laboratory studies. While most research has focused on cancer and cardiovascular applications, newer investigations are examining citrus polyphenol effects on cognitive function, including learning and memory.

An increasing number of studies have also shown a greater absorption of the nutrients in citrus when taken not as singly as supplements, but when consumed within the fruit in which they naturally appear along with all the other biologically active phytonutrients that citrus fruits contain.

Long-acting limonoids in citrus

In animal studies and laboratory tests with human cells, compounds in citrus fruits, including oranges, called limonoids have been shown to help fight cancers of the mouth, skin, lung, breast, stomach and colon. Now, scientists from the US Agricultural Research Service have shown that the human body can readily absorb and utilize a very long-acting limonoid called limonin that is present is citrus fruits in about the same amount as vitamin C.

In citrus fruits, limonin is present in the form of limonin glucoside, in which limonin is attached to a sugar (glucose) molecule. The human body easily digests this compound, cleaving off the sugar and releasing limonin.

In the ARS study, 16 volunteers were given a dose of limonin glucoside in amounts ranging from those that would be found in from 1 to 7 glasses of orange juice. Blood tests showed that limonin was present in the plasma of all except one of the subjects, with concentrations highest within 6 hours after consumption. Traces of limonin were still present in 5 of the volunteers 24 hours after consumption!

Limonin’s bioavailability and persistence may help explain why citrus limonoids are potent anti-carcinogens that may continuously prevent cancerous cells from proliferating. Other natural anti-carcinogens are available for much less time; for example, the phenols in green tea and chocolate remain active in the body for just 4 to 6 hours.

Oranges’ possible cholesterol-lowering benefits

The ARS team is now investigating the potential cholesterol-lowering effects of limonin. Lab tests indicate that human liver cells produce less apo B when exposed to limonin. Apo B is a structural protein that is part of the LDL cholesterol molecule and is needed for LDL production, transport and binding, so higher levels of apo B translate to higher levels of LDL cholesterol.

Compounds in orange peel may lower cholesterol as effectively as statin drugs

A class of compounds found in citrus fruit peels called polymethoxylated flavones (PMFs) have the potential to lower cholesterol more effectively than some prescription drugs, and without side effects, according to a study by U.S. and Canadian researchers that was published in the Journal of Agricultural and Food Chemistry.

In this study, when laboratory animals with diet-induced high cholesterol were given the same diet containing 1% PMFs (mainly tangeretin), their blood levels of total cholesterol, VLDL and LDL (bad cholesterol) were reduced by 19-27 and 32-40% respectively. Comparable reductions were also seen when the animals were given diets containing a 3% mixture of two other citrus flavonones, hesperidin and naringin.

Treatment with PMFs did not appear to have any effect on levels of beneficial HDL cholesterol, and no negative side effects were seen in the animals fed the PMF-containing diets.

Although a variety of citrus fruits contain PMFs, the most common PMFs, tangeretin and nobiletin, are found in the peels of tangerines and oranges. Juices of these fruits also contain PMFs, but in much smaller amounts. In fact, you’d have to drink about 20 glasses of juice each day to receive an amount of PMFs comparable in humans to that given to the animals. However, grating a tablespoon or so of the peel from a well-scrubbed organic tangerine or orange each day and using it to flavor tea, salads, salad dressings, yogurt, soups, or hot oatmeal, buckwheat or rice may be a practical way of achieving some cholesterol-lowering benefits. The researchers are currently exploring the mechanism of action by which PMFs lower cholesterol. Based on early results in cell and animal studies, they suspect that PMFs work like statin drugs, by inhibiting the synthesis of cholesterol and triglycerides inside the liver.

Oranges are a very good source of fiber

Oranges’ health benefits continue with their fiber, which has been shown to reduce high cholesterol levels thus helping to prevent atherosclerosis. Fiber can also help out by keeping blood sugar levels under control, which may help explain why oranges can be a very healthy snack for people with diabetes. In addition, the natural fruit sugar in oranges, fructose, can help to keep blood sugar levels from rising too high after eating. The fiber in oranges can grab cancer-causing chemicals and keep them away from cells of the colon, providing yet another line of protection from colon cancer. And the fiber in oranges may be helpful for reducing the uncomfortable constipation or diarrhea in those suffering from irritable bowel syndrome.

In addition to oranges’ phytonutrients, vitamin C, and fiber, they are a good source of folate, vitamin A (in the form of carotenoids), vitamin B1, potassium, copper, pantothenic acid, and calcium.

Oranges possible prevention of kidney stones

Want to reduce your risk of calcium oxalate kidney stones? Drink orange juice. A study published in the British Journal of Nutrition found that when women drank 1/2 to 1 litre of orange, grapefruit or apple juice daily, their urinary pH value and citric acid excretion increased, significantly dropping their risk of forming calcium oxalate stones.

Oranges may prevent ulcers and reduce risk for stomach cancer

An orange a day may help keep ulcers away, according to a study published in the Journal of the American College of Nutrition. In this study, researchers evaluated data from over 6,000 adults enrolled in the Third National Health and Nutrition Examination Survey. Study participants with the highest blood levels of vitamin C had a 25% lower incidence of infection with Helicobacter pylori (H. pylori), the bacterium responsible for causing peptic ulcers and in turn, an increased risk for stomach cancer. Researchers are uncertain whether H. pylori lowers blood levels of vitamin C or if high blood levels of vitamin C help protect against infection—either way, eating an orange or drinking a glass of orange juice each day may help prevent gastric ulcers. Lead researcher in this study, Dr. Joel A. Simon at the San Francisco VA Medical Center, urges people who have tested positive for H. pylori to increase their consumption of vitamin C-rich foods since this may help them combat H. pylori infection.

Oranges may protect respiratory health

Consuming foods rich in beta-cryptoxanthin, an orange-red carotenoid found in highest amounts in oranges, corn, pumpkin, papaya, red bell peppers, tangerines, and peaches, may significantly lower one’s risk of developing lung cancer. A study published in the September 2003 issue of Cancer Epidemiology, Biomarkers and Prevention reviewed dietary and lifestyle data collected from over 60,000 adults in Shanghai, China. Those eating the most crytpoxanthin-rich foods showed a 27% reduction in lung cancer risk. When current smokers were evaluated, those who were also in the group consuming the most cryptoxanthin-rich foods were found to have a 37% lower risk of lung cancer compared to smokers who ate the least of these health-protective foods.

Oranges may offer protection against rheumatoid arthritis

New research published in the American Journal of Clinical Nutrition adds to the evidence that enjoying a daily glass of freshly squeezed orange juice can significantly lower your risk of developing rheumatoid arthritis.

Data collected by the European Prospective Investigation of Cancer Incidence (EPIC)-Norfolk study, a population-based, prospective study of over 25,000 subjects, showed that study participants with the highest daily intake of the carotenoids, zeaxanthin and beta-cryptoxanthin, had a much lower risk of developing rheumatoid arthritis compared to individuals consuming the least of these beneficial phytonutrients. Those whose intake of zeaxanthin was highest were 52% less likely to develop rheumatoid arthritis, while those with the highest intake of cryptoxanthin had a 49% reduction in risk. A single daily glass of freshly squeezed orange juice could account for much of this observed reduction.

Description

Oranges rank among the most widely consumed fruits globally. For many Americans, orange juice is virtually synonymous with breakfast.

These round citrus fruits have finely-textured skins and pulpy flesh, both characteristically orange. They typically measure two to three inches in diameter.

Oranges are classified into two general categories—sweet and bitter—with the former being the type most commonly consumed. Popular varieties of the sweet orange (Citrus sinensis) include Valencia, Navel and Jaffa oranges, as well as the blood orange, a hybrid species that is smaller in size, more aromatic in flavor and has red hues running throughout its flesh. Bitter oranges (Citrus aurantium) are oftentimes used to make jam or marmalade, and their zest serves as the flavoring for liqueurs such as Grand Marnier and Cointreau.

History

Oranges originated thousands of years ago in Asia, in the region from southern China to Indonesia from which they spread to India. Although Renaissance paintings display oranges on the table in paintings of The Last Supper, the assumption that they were grown in this region at this time seems to be erroneous since oranges were not cultivated in the Middle East until sometime around the 9th century. Sweet oranges were introduced into Europe around the 15th century by various groups including the Moors, and the Portuguese as well as the Italian traders and explorers who found them on their voyages to Asia and the Middle East.

Orange trees began to be grown in the Caribbean Islands in the late 15th century after Christopher Columbus brought the seeds there on his second voyage to the New World. Spanish explorers are responsible for bringing oranges to Florida in the 16th century, while Spanish missionaries brought them to California in the 18th century, beginning the cultivation of this citrus fruit in the two states widely known for their oranges.

Before the 20th century, oranges were very expensive and therefore they were not regularly consumed, but rather eaten on special holidays such as Christmas. After more efficient means of transportation were developed, and food processors invented methods for utilizing orange by-products such as citric acid and bioflavonoids, the price of oranges dropped, and they could be consumed on a wide scale, as they are today. Currently, the countries that are some of the largest commercial producers of oranges include the United States, Brazil, Mexico, Spain, China and Israel.

How to select and store

Oranges do not necessarily have to have a bright orange color to be good. In fact, the uniform color of non-organic oranges may be due to injection of Citrus Red Number 2 (an artificial dye) into their skins at the level of 2 parts per million. Whether organic or not, oranges that are partially green or have brown russetting may be just as ripe and tasty as those that are solid orange in color. Avoid those that have soft spots or traces of mold. And, because oranges are among the top 20 foods in which pesticide residues are most frequently found, buy organic oranges whenever possible.

Choose oranges that have smoothly textured skin and are firm and heavy for their size. These will have a higher juice content than those that are either spongy or lighter in weight. In general, oranges that are smaller will be juicier than those that are larger in size, as will those that feature thinner skins.

Certified organic oranges reduce exposure to pesticide residues and heavy metals. In supermarkets, look for the USDA organic logo.

Oranges can either be stored at room temperature or in the refrigerator, depending upon your preference. They will generally last the same amount of time, two weeks with either method, and will retain nearly the same level of their vitamin content. The best way to store oranges is loose rather than wrapped in a plastic bag since if exposed to moisture, they can easily develop mold.

Orange juice and zest can also be stored for later use. Place freshly squeezed orange juice in ice cube trays until frozen, and then store them in plastic bags in the freezer. Dried orange zest should be stored in a cool, dry place in an airtight glass container.

Tips for preparing and cooking

Preparation

Oranges can be eaten as a snack: peel and enjoy. Before cutting the orange in half horizontally through the center, wash the skin so that any dirt or bacteria residing on the surface will not be transferred to the fruit. Proceed to cut the sections into halves or thirds, depending upon your personal preference.

Thin-skinned oranges can be easily peeled with your fingers. For easy peeling of the thicker skinned varieties, first cut a small section of the peel from the top of the orange. You can then either make four longitudinal cuts from top to bottom and peel away these sections of skin, or starting at the top, peel the orange in a spiral fashion.

Oranges are oftentimes called for in recipes in the form of orange juice. As oranges, like most citrus fruits, will produce more juice when warmer, always juice them when they are at room temperature. Rolling the orange under the palm of your hand on a flat surface will also help to extract more juice.

The juice can be extracted in a variety of ways. You could either use a juicer or do it the old fashioned way, squeezing by hand.

If your recipe calls for orange zest, make sure that you use an orange that is organically grown since most conventionally grown fruits will have pesticide residues on their skin and may be artificially colored. After washing and drying the orange, use a zester, paring knife or vegetable peeler to remove the zest, which is the orange part of the peel. Make sure not to remove too much of the peel as the white pith underneath is bitter and should not be used. The zest can then be more finely chopped or diced if necessary.

How to enjoy

Serving ideas

• Healthy sauté onions and ginger, and then deglaze the pan with orange juice. Use this liquid as a sauce for salmon or tuna.
• Orange segments, fennel and boiled beets make a delightfully refreshing salad.
• Gently simmer sweet potatoes, winter squash and orange segments in orange juice. Before serving, sprinkle with walnuts.

For more recipe ideas, see Recipes.

Nutritional profile

One medium (131g) at 62 calories provides vitamin C (93% DV), fiber (11% DV), folate (10% DV). Smaller but measurable amounts of vitamin B1 (9% DV), copper (7% DV), pantothenic acid (7% DV), vitamin A (5.9% DV), calcium (5% DV), potassium (5% DV) round out the profile.

Individual concerns