vitamin C

vitamin C Ascorbic acid. Historically an inadequate intake of vitamin C led to scurvy, especially common among sailors unable to obtain fruits and vegetables. It has three main areas of function: (1)as a general (non‐enzymic) antioxidant, including the reduction of oxidized vitamin E in cell membranes;(2)as a coenzyme in the hydroxylation of lysine and proline in the synthesis of collagen and elastin, and hence essential for the normal formation of connective tissue;(3)as a coenzyme in the formation of noradrenaline.

Deficiency results in scurvy: seepage of blood from capillaries, subcutaneous bleeding, weakness of muscles, soft, spongy gums and loss of dental cement leading to loss of teeth, and, in advanced cases, deep bone pain. A lesser degree of deficiency results in impaired healing of wounds. The requirement to prevent scurvy is less than 10 mg/d; reference intakes are 30 mg/d (FAO); 40 mg/d (UK); 45 mg/d (EU); 90 mg/d (USA). All these differing figures can be justified, depending on the criteria of adequacy adopted and the assumptions made in the interpretation of experimental data. At intakes above 100–120 mg/d the vitamin is excreted in the urine; there is no evidence of any adverse effects at intakes up to 4000 mg/d.

Losses from foods can be high as they stale; it is easily oxidized, especially in foods kept hot, and it is leached into cooking water. Fruits and vegetables are rich sources. It is also used in curing ham, and as an antioxidant and bread improver. See also erythorbic acid; iron.