Vitamin C is a water-soluble antioxidant required by every tissue in the body. First isolated in 1928 by Albert Szent-Gyorgi, vitamin C is involved in hundreds of vital biochemical reactions and is the body's most important antioxidant, serving as the first line of defense against free-radical induced damage. While most animals manufacture their own vitamin C, in humans this is not the case; it must be included in the diet. Because it is a water-soluble vitamin and is not stored in the body, it is essential that people consume vitamin C daily. Supplemental vitamin C is sold in many forms, including powders, timed-release tablets, capsules, etc. Non-acidic, "buffered" forms, in which ascorbic acid is bonded to a mineral (i.e. calcium, potassium, sodium, and magnesium ascorbates) are available for those who experience gastric discomfort with regular vitamin C supplements.
Good food sources of vitamin C include citrus fruits, broccoli, peppers, tomatoes, and dark-green, leafy vegetables like spinach and kale.
The primary function of vitamin C is in the manufacture of collagen, which is the main protein substance in human tissues. This makes vitamin C important for virtually all body systems. Vitamin C is essential for healthy skin, gums, blood vessels, eyes, central nervous system and reproductive function. It is also required for the production of enzymes that help rid the body of toxins, including lead and other environmental pollutants.
The RDA for vitamin C is 60 mg per day, but this is widely believed to be too low. Many nutritionists recommend 250 to 500 mg per day for healthy people, but doses of up to 5,000 mg per day have been recommended in conditions of increased oxidative stress. Factors that increase vitamin C requirements include smoking, diabetes, high-fat diets, physical wounds, infections, and many illnesses. Vitamin C is absorbed more efficiently when consumed with bioflavonoids, and they may also enhance its antioxidant potency. Because vitamin C is not stored in the body, it is best to consume it in divided doses throughout the day, preferably with meals. Vitamin C has no known toxicity, even at extremely high doses. Adverse effects including stomach upset, intestinal gas and diarrhea have been reported with high-dose supplementation, but these symptoms normally reverse with reduction of intake.