Vitamin C

water-soluble, carbohydrate-like substance that is involved in certain metabolic processes of animals. Although most animals can synthesize vitamin C, it is necessary in the diet of some, including humans and other primates, in order to prevent scurvy, a disease characterized by soreness and stiffness of the joints and lower extremities, rigidity, swollen and bloody gums, and hemorrhages in the tissues of the body. First isolated in 1928, vitamin C was identified as the curative agent for scurvy in 1932.

Vitamin C is essential for the synthesis of collagen, a protein important in the formation of connective tissue and in wound healing. It acts as an antioxidant, protecting against damage by reactive molecules called free radicals. The vitamin also helps in stimulating the immune system. It has been shown in animal trials that vitamin C has some anticarcinogenic activity.

Relatively large amounts of vitamin C are required—for instance, an adult man is said to need about 70 mg (1 mg = 0.001 gram) per day. Citrus fruits and fresh vegetables are the best dietary sources of the vitamin. Because vitamin C is easily destroyed by reactions with oxygen, especially in neutral or alkaline solution or at elevated temperatures, it is difficult to preserve in foods. The vitamin is added to certain fruits to prevent browning. (&See; table of the vitamins.)