Unlike other water-soluble vitamins, vitamin C (ascorbic acid), does not appear to act either as a catalyst or as a coenzyme. Instead, it plays a major role by regulating the formation of collagen. Collagen is a protein that makes up connective tissue. This tissue is found in skin, bones, cartilage, teeth, muscles and the walls of blood vessels. Vitamin C is also an important antioxidant. It helps protect vitamin A, vitamin E , and various fatty acids from the damage caused by excessive oxidation.
Because very little vitamin C is stored in the body, a daily dietary source is necessary. The vitamin is found almost exclusively in fruits and vegetables, particularly in citrus fruits such as oranges and lemons.
Interestingly, most animals are able to synthesize their own vitamin C. Only primates, guinea pigs, and a few fairly exotic creatures (such as the Indian fruit bat) need to get this vitamin from food.
Today cereals, infant formulas, and other foods are often supplemented with vitamin C, so that a serious deficiency is quite rare. Vitamin C deficiencies were common up until the early 20th century. They generally occurred during the winter months, occasionally lasting long enough to produce scurvy.
Scurvy is a debilitating and potentially fatal disease caused by a prolonged lack of vitamin C, leading to problems with the body's connective tissues. An early symptom of scurvy occurs when the walls of the smaller blood vessels become dangerously fragile and begin to rupture. The patient's gums bleed and small hemorrhagic spots appear on the skin. In later stages, teeth loosen and fall out, bones weaken, joints become swollen and painful, and anemia may develop. Additionally, wounds fail to heal because connective tissue is needed to repair cuts in the skin. Unless the disease process is halted, death results.