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Vitamin C (ascorbic acid) is a water-soluble vitamin which is the key antioxidant in the human body. It has been included on the WHO List of Essential Medicines, as it is used to treat scurvy, i.e. a disease causing an error in collagen creation due to a lack of ascorbic acid. Contrary to popular belief, regular intake of vitamin C as a nutritional supplement does not prevent one from getting a cold, but may shorten recovery time. Foods containing large amounts of vitamin C are citrus fruits, tomatoes, red peppers, and potatoes.
Vitamin C may be obtained with food in two forms, i.e. as ascorbic acid, which is a powerful reducer, or in oxidised form as dehydroascorbic acid. Although vitamin C is found in body fluids mostly in reduced form, ascorbic acid and dehydroascorbic acid are both biologically active and transform from one form to another during oxidation and reduction reactions catalysed by enzymes in the body.