Sweet, juicy oranges make a delicious and healthy snack or addition to a meal. A whole orange contains only about 60 calories and has no fat, cholesterol or sodium, and, "oranges are well known for their vitamin C content," said Laura Flores, a San Diego-based nutritionist.

Indeed, oranges offer many health benefits: They may boost your immune system, give you better skin, and even help improve your health heart and cholesterol levels. In addition, some evidence suggests that eating oranges may help reduce the risk of respiratory diseases, certain cancers, rheumatoid arthritis, ulcers and kidney stones.

Orange juice is also packed with nutrients. However, the juice doesn't contain the fiber found in the orange pith, the white substance between the peel and the flesh. It's also easier to consume too many calories when drinking orange juice than when eating an orange, according to the U.S. Centers for Disease Control and Prevention.

Health benefits of oranges

Most citrus fruits have a good deal of vitamin C, and oranges have high levels even compared to their tangy brethren. Vitamin C, a potent antioxidant, protects cells by scavenging and neutralizing harmful free radicals, according to a 2018 review published in the journal Advances in Analytical and Pharmaceutical Chemistry.

Free radicals are reactive atoms that can form from things such as environmental pollution, cigarette smoke and stress, and exposure to a high level of free radicals may lead to chronic conditions such as cancer and heart disease.

The vitamin C in oranges may also boost a person's immunity to everyday viruses and infections such as the common cold, according to the same review.

Some research suggests that the vitamin C in oranges may be linked with a lower risk of certain cancers.

"The vitamin C in oranges is associated with a reduced risk of colon cancer due to preventing DNA mutations from taking place," Flores said. Studies have shown that about 10 to 15 percent of colon cancers have a mutation in a gene called BRAF.

In addition, a 2013 study published in the journal Nutrition and Cancer found that the high amounts of vitamin C and folic acid, coupled with the antioxidant properties, in orange juice can reduce DNA damage and, therefore, the risk of cancer.

In addition to vitamin C, oranges contain fiber, potassium and choline, all of which are good for your heart. Potassium, an electrolyte mineral, is vital for the healthy functioning of the nervous system, and a lack of potassium can lead to arrhythmia (an irregular heartbeat), increased blood pressure and a depletion of calcium in bones, according to the U.S. National Institutes of Health.

"The potassium found in oranges helps to lower blood pressure, protecting against stroke," Flores said. Too much potassium, however, can lead to hyperkalemia which can be serious and life threatening and include symptoms of muscle fatigue and weakness, nausea and paralysis, according to the Mayo Clinic.

Flores also noted that oranges are high in folate, a B vitamin that helps the body lower levels of homocysteine, an amino acid that is common in red meat and is linked with poor heart health.

The fiber in oranges may help lower blood sugar levels in people with type 1 diabetes and improve blood sugar, lipids and insulin levels in people with type 2 diabetes. The American Diabetes Association lists oranges, along with other citrus fruits, as a "superfood" for people with diabetes.

Fiber also aids in digestion and may help lower cholesterol by blocking the absorption of cholesterol into the bloodstream, according to the Mayo Clinic.

Health risks

Oranges are great for you, but you should enjoy them in moderation, Flores said. "Eating too many oranges has some uncomfortable side effects," she said. "When [oranges are] eaten in excess, the greater fiber content can affect digestion, causing abdominal cramps, and could also lead to diarrhea."

Though oranges are relatively low in calories, eating several per day can end up leading to weight gain. It is also possible to consume too much vitamin C (more than 2,000 milligrams a day); an excess of this nutrient may lead to diarrhea, nausea, vomiting, heartburn, bloating or cramps, headaches and insomnia, according to the Mayo Clinic.

"Because they are a high-acid food, [oranges] can contribute to heartburn, especially for those who already suffer [from heartburn] regularly," Flores said. People with gastroesophageal reflux disease (GERD, also called acid reflux disease) may experience heartburn or regurgitation if they eat too many oranges.

People who are taking beta-blockers (a type of medication used to treat high blood pressure) should be careful not to consume too many fruits that are high in potassium, such as oranges and bananas, according to the American Heart Association. These medicines increase potassium levels and, if mixed with large amounts of potassium-rich foods, can lead to an excess of potassium in the body. This is a significant concern for people whose kidneys are not fully functional, as the additional potassium will not be effectively removed from the body.

Orange peels: eat 'em or leave 'em??

Orange peels are not poisonous, and as many cooks know, orange zest can pack a big flavor punch. But although orange peels are edible, they are not nearly as sweet or as juicy as the pulp. They can also be difficult to digest, and unless you're eating a peel from an organic orange, it could be covered in chemicals.

If you do eat the peel, you'll get a good amount of nutrients. "Orange peel actually has more fiber than the fruit inside," Flores said. "It also has flavonoids in it that contain nutritious benefits."

Flavonoids — compounds found in many foods, such as fruits and vegetables, grains, tea and wine — are known to lower blood pressure and reduce inflammation, according to a 2016 article published in the Journal of Nutritional Science.

Additionally, orange peels contain calcium, several B vitamins, and vitamins A and C. You can get the same nutrients by eating the inner part of the peel and leaving the tough outer part.

"The pith of the orange — the white part between the skin and fruit — can be sour or bitter but actually contains just as much vitamin C as the fruit itself, with a good deal of fiber," Flores said.

Orange facts

• Oranges originated around 4000 B.C. in Southeast Asia and then spread to India.
• Oranges are a hybrid of the pomelo, or "Chinese grapefruit" (which is pale green or yellow), and the tangerine.
• The orange tree is a small tropical to semitropical, evergreen, flowering plant. It grows up to 16 to 26 feet (5 to 8 meters).
• Oranges are classified into two general categories: sweet and bitter. The sweet varieties are the most commonly consumed. Popular varieties of the sweet orange (Citrus sinensis) include Valencia, navel and Jaffa oranges. Bitter oranges (Citrus aurantium) are often used to make jam or marmalade, and their zest is used as the flavoring for liqueurs such as Grand Marnier and Cointreau.
• Renaissance paintings that display oranges on the table during "The Last Supper" are wrong. Oranges were not cultivated in the Middle East until sometime around the ninth century.
• Commercial oranges are often bright orange because an artificial dye, Citrus Red Number 2, is injected into their skins at a concentration of 2 parts per million.
• In 2017, the top five orange-producing countries, by millions of tons produced, were Brazil (35.6), the United States (15.7), China (14.4), India (10.8) and Mexico (8.1).

• About 85 percent of all oranges produced are used for juice.
• There are over 600 varieties of oranges worldwide.

By Jessie Szalay, Live Science