Vitamin C, also known as ascorbic acid, is a water soluble antioxidant that reacts directly with superoxide, hydroxyl radicals, and singlet oxygen. Vitamin C readily undergoes reversible oxidation and reduction in the body and has been shown to regenerate other antioxidants within the body, including alpha-tocopherol. It decreases oxidants in gastric secretions which may protect lipids in plasma and against peroxidative damage. Ascorbic acid is absorbed in the small intestine by a sodium-dependent transport process that is intake dependent. It is a specific electron donor for enzymes that participate in collagen hydroxylation and carnitine biosynthesis. This function is required to catalyze the crosslinking of collagen fibers which are essential for normal wound healing and capillary health. Vitamin C also appears to prevent inactivation of nitric oxide (NO)- mediated vasodilation. ‡
In addition to its biosynthetic and antioxidant functions, vitamin C plays an important role in immune function and improves the absorption of nonheme iron, the form of iron present in plant-based foods. Taking at least 200 mg of vitamin C per 30 mg of iron together increases nonheme iron absorption in adults. In children, adding 25-50 mg of Vitamin C daily can increase iron absorption from a meal by 3.2- 4.8-fold compared to eating the meal alone.