When most people think of Vitamin C in foods, their minds go immediately to citrus fruits, especially oranges. While citrus fruits are a good source of Vitamin C, some other fruits have even more of this health-promoting vitamin. Juices, rather than the whole fruit, are a quick way to get Vitamin C, but the vitamin content degrades over time after juicing.
Definitions
Vitamin C is a term for the chemical ascorbic acid. In processed citrus products, additional Vitamin C may be added, labeled as ascorbic acid. Citrus fruits include oranges and related fruits such as tangerines and satsumas, limes, lemons, grapefruit, kumquats and many others not commonly available in Western markets.
Significance
Christine Economos and William D. Clay found during their review of scientific studies that Vitamin C is vital for collagen, which is a part of bones, skin, ligaments, blood vessels and tendons. Vitamin C is an antioxidant that has also been linked to prevention of cancer, cardiovascular disease and cataracts. To prevent scurvy, humans need at least 10 mg of Vitamin C per day, though ideally, consumption should be higher. Estimates of Vitamin C needs for adult humans range from 30 to 200 mg per day. Someone who consumes at least five servings of fruits and vegetables each day will generally consume about 200 mg of Vitamin C each day.
Comparison
Yellow kiwifruit and tropical guavas, neither of which are citrus fruits, actually have more Vitamin C than oranges. One orange has about 70 mg of Vitamin C, one yellow kiwifruit has 108 to 162 mg and one tropical guava has 165 mg. However, a 225 ml, or 8 ounce, glass of orange juice has 125 mg. Grapefruit, lemons and limes all have significantly less Vitamin C.
Deterioration
Though orange juice has a higher concentration of Vitamin C per serving than oranges, Vitamin C in orange juice and all citrus juices deteriorates over time. One study, Vitamin C and the Role of Citrus Juices as Functional Food, reports that temperature and oxidation are the primary influencers of Vitamin C loss, with higher levels causing greater Vitamin C loss. Glass or metal containers preserve the Vitamin C in citrus juices much better than plastic containers.
Overconsumption
Generally, taking moderate doses of Vitamin C is not harmful. Consuming over 500 mg of Vitamin C per day may be harmful if you are at risk of ingesting too much iron, as ascorbic acid can increase your body's metabolism of iron. However, to reach this level you would have to take Vitamin C supplements or eat several oranges and other citrus fruits every day. Individuals consuming high doses of Vitamin C may also experience gastrointestinal upsets such as diarrhea.
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