Long recognized as a potent source of vitamin C, oranges are considered by most to be tasty, juicy, and unspectacular. No one gets excited about an orange in their lunchbox-but they should. The discoveries that are being made about the power of oranges to support heart health and prevent cancer, stroke, diabetes, and a host of chronic ailments should bring oranges and other citrus fruits back to center stage as crucial components in a health promoting and preventative diet.
Humans (and guinea pigs) can't manufacture vitamin C. It's water soluble and not retained in the body, so we need a constant replenishment from dietary sources to maintain adequate cellular and blood levels. Alarmingly, a high percentage of children consume minimal amounts of vitamin C. The recommended daily allowance (RDA) for North Americans is 90 milligrams a day for adult males and 75 milligrams a day for adult females.
It's fairly shocking that, given today's abundance of food, so many of us are deficient in a vitamin that's crucial to good health. While we might not be seeing cases of scurvy anymore, we're certainly seeing epidemic numbers of heart disease, hypertension, and cancer. The vitamin C in citrus, along with the other valuable nutrients, can play a major role in reducing these high levels of chronic disease.
Flavonoids are a class of polyphenols found in fruits, vegetables, legumes, nuts, seeds, grains, tea, and wine. There are over five thousand flavonoids that have been identified and described in scientific literature, and we're learning more about them every day.
Citrus flavonoids, which are found in the fruit's flesh, juice, pulp, and skin, are one of the reasons for the health-promoting attributes of citrus fruits and the reason that the whole fruit is so much more healthful than just the juice. Two of the flavonoids in citrus-naringin in grapefruit and hesperidin in oranges- occur only rarely in other plants and are thus essentially unique to citrus. The power of citrus flavonoids is dazzling. They're antioxidant and antimutagenic. The latter refers to their ability to prevent cells from mutating and initiating one of the first steps in the development of cancer and other chronic diseases. This is accomplished by their apparent ability to absorb ultraviolet light, protect DNA, and interact with carcinogens. Citrus flavonoids have been shown to inhibit cancer cell growth, strengthen capillaries, act as an anti-inflammatory, and they're antiallergenic and antimicrobial. Flavonoid intake is inversely associated with the incidence of heart attack and stroke as well as a host of other ailments.
We're certain that an orange a day promotes cardiovascular health. The Framingham Nurses' Health Study found that drinking one daily glass of orange juice reduced the risk of stroke by 25 percent. Countless other studies have confirmed similar benefits from regular consumption of citrus. We're beginning to understand that, as with so many Superfoods, it's the synergy of multiple foods and the variety of nutrients they contain that combine to amplify and intensify individual benefits.
For example, oranges are rich in vitamin C. They are also rich in flavonoids, such as hesperidin, that work to revive vitamin C after it has quash free radicals. In other words, the hesperidin strengthens and amplifies the effect of vitamin C in your body. In an interesting human clinical trial, orange juice was shown to elevate HDL cholesterol (good") cholesterol while lowering LDL (so-called bad) cholesterol.
The fibre in oranges is another major contributor to heart health. Citrus fruit (especially tangerines) are one of the richest sources of high-quality pectin-a type of dietary fibre. Pectin is a major component of the kind of fibre that's known to lower cholesterol. Pectin is also helpful in stabilizing blood sugar. A single orange provides 3 grams of fibre, and dietary fibre has been associated with a wide range of health benefits. About 35 percent of North Americans consume their fruit only in juice form. In most cases, their health would benefit if they would just add whole fruit whenever possible.
Recent news from researchers has demonstrated that oranges can play a significant role in preventing cancer. We know, for example, that the Mediterranean diet, which includes a considerable amount of citrus, is associated with low incidences of cancers of the breast, lung, pancreas, colon, rectum, and cervix. Indeed, citrus fruits have been found to contain numerous known anticancer agents-possibly more than any other food. The National Cancer Institute calls oranges a complete package of every natural anticancer inhibitor known.
One particular phytonutrient has attracted attention lately as a health-promoting agent. Amazingly, we routinely throw out this most potent part of the orange. In the oil of the peel of citrus fruits is a phytonutrient known as limonene. Oranges, mandarins, lemons, and limes contain significant amounts of limonene in the peel and smaller quantities in the pulp. Limonene stimulates our antioxidant detoxification enzyme system, thus helping to stop cancer before it can even begin. (It's reassuring to know that a natural chemopreventive phytonutrient can work to prevent the process of carcinogenesis at the earliest stages). Limonene also reduces the activity of proteins that can trigger abnormal cell growth. Limonene has blocking and suppressing actions that, at least in animals, actually cause regression of tumors. One study of people in Arizona found that those who used citrus peels in cooking reduced their risk of squamous cell carcinoma by 50 percent.
We've long known that Mediterranean people suffer lower rates of certain cancers than others, and researchers now believe this can partly be ascribed to their regular consumption of citrus peel. Orange juice does contain some limonene but not nearly as much as the peel. Fresh-squeezed juice has the most limonene, along with other nutrients, and orange juice pulp has 8 to 10 percent more limonene than juice with no pulp.
Vitamin C, abundantly available in oranges, also plays a role in fighting cancer. In fact, there's a relatively consistent inverse association of vitamin C with cancer of the stomach, oral cancer, and cancer of the oesophagus. This makes sense, as vitamin C protects against nitrosamines, cancer-causing agents found in foods that are thought to be responsible for instigating cancers of the mouth, stomach, and colon. One study of Swiss men found that those who died of any type of cancer had vitamin C concentrations about 10 percent lower than those who died from other causes.
Citrus seems to have a protective ability against stroke. In the Men's Health Professionals Follow-Up Study, citrus and citrus juice were major contributors to the stroke-risk reduction from fruits and vegetables. It has been estimated that drinking one glass of orange juice daily may lower the risk of stroke in healthy men by 25 percent while the risk is reduced only ii percent from other fruits.
It's very interesting that consumption of vitamin C in supplement form does not appear to have the same benefits as the whole fruit when it comes to stroke prevention. This suggests that there must be some other protective substance(s) in citrus juices to account for their power to protect from strokes. The current assumption at this point is that it's the power of the polyphenols that make the difference. Another reason to rely on whole foods for optimal nutrition! On the other hand, more than 350 to 400 milligrams a day of supplemental vitamin C for a period of at least ten years seems to be an effective means of lowering your risk of developing cataracts. (This is one instance where supplements do work.)
