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Q It seems that eating fruit and getting painful canker sores go hand-in-hand. Is there any way I can keep from getting the sores without giving up the fruit?

A Fruit is not the cause of your canker sores. You may be associating fruit with canker sore pain because citrus fruits (as well as other high-acid foods) can exacerbate the discomfort canker sores produce. The exact cause of canker sores--ulcers in the lining of the mouth--is unknown. However, stress, fatigue, allergies, and minor mouth injuries like those that come from biting one's cheek seem to increase the chances of getting them. Also, women are more prone to developing canker sores than men. Unfortunately, canker sores tend to be recurrent, and no cure exists. To lessen the pain of your next canker sore (or cluster of sores), try avoiding acidic, very hot, and spicy foods since they can further irritate the delicate tissues affected. Non-prescription, topical anesthetics, such as Anbesol, may also provide temporary relief, as can pain relievers like Zilactin and Orajel Mouth-Aid. In some cases, anti-inflammatory drugs, including steroids in the form of gels or mouth rinses, are prescribed to quell the inflamed area. With or without drugs, canker sores heal in a week or two.

Q How is orange juice concentrate made? If heat is used in the process, isn't the vitamin C destroyed?

A Heat, used to make orange juice concentrate, does generally destroy vitamin C, but not in this particular case. Edwin Moore, PhD, of the Florida Department of Citrus, explains that the evaporation of the liquid in the juice requires heating at about 200 degrees Fahrenheit for only 6 seconds or so--not enough time to have an impact on the nutrient's composition. The high acidity of orange juice also protects the vitamin C it contains.

The upshot is that both frozen orange juice concentrate and refrigerated orange juice made from concentrate contain 97 to 100 percent of the vitamin C that was originally in the oranges used to make them. Of course, the longer orange juice is kept in the refrigerator, the more vitamin C it loses. The nutrient degrades over time.

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