Vitamin C, or Ascorbic Acid, is synthesized from glucose and galactose by plants and most animals. However, humans, other primates, guinea pigs, some bats, and a few species of birds, lack the enzyme lgulonolactone oxidase and thus cannot biosynthesize the factor; for them, it is a vitamin.
During collagen and carnitine synthesis, vitamin C acts as a reducing agent to keep iron in its ferrous state, thus enabling hydroxylation enzymes to function.
Cellular vitamin C deficiency may lead to oxidative stress in cells, contributing to an increased risk of ischemic heart disease. During periods of emotional, psychological, or physiologic stress, the urinary excretion of ascorbic acid increases. It also reduces ferric to ferrous iron in the intestinal tract to facilitate iron absorption and is involved in the transfer of iron from plasma transferrin to liver ferritin.
Vitamin C promotes resistance to infection through its involvement with the immunologic activity of leukocytes, the production of interferon, the process of inflammatory reaction, and the integrity of the mucous membranes. Vitamin C maintains proper lung function, especially in asthma.
Vitamin C is found in plants and animal tissues as ascorbic acid and dehydroascorbic acid. The best sources are fruits, vegetables, and organ meats, but the actual ascorbic acid contents of foods can vary with the conditions of growth and degree of ripeness when harvested.
Acute vitamin C deficiency results in scurvy in individuals unable to synthesize the vitamin. In human adults signs are manifest after 45 to 80 days of vitamin C deprivation. In children the syndrome is called Moeller-Barlow disease; it can also develop in infants fed formulas not enriched with vitamin C. In both cases lesions occur in mesenchymal tissues and result in impaired wound healing; edema; hemorrhages; and weakness in bone, cartilage, teeth, and connective tissues. Adults with scurvy may have swollen, bleeding gums with eventual tooth loss, lethargy, fatigue, rheumatic pains in the legs, muscular atrophy, skin lesions, and a variety of psychological changes.
15-120 mg/day, depending on age and gender