Vitamin C, a water-soluble vitamin, is essential for the synthesis of collagen and intercellular material. Vitamin C deficiency develops when the dietary intake is inadequate. It is rare in adults, but may occur in infants, alcoholics, or the elderly. Deficiency leads to the development of a well-defined syndrome known as scurvy. This is characterized by capillary fragility, bleeding (especially from small blood vessels and the gums), normocytic or macrocytic anaemia, cartilage and bone lesions, and slow healing of wounds.
Vitamin C is used in the treatment and prevention of deficiency. It completely reverses symptoms of deficiency. It is usually given by mouth, the preferred route, as ascorbic acid, and has been given to children in the form of a suitable fruit juice such as orange juice or as black currant or rose hip syrups. Ascorbic acid or sodium ascorbate may be given parenterally, preferably by the intramuscular route, but also by the intravenous or subcutaneous routes. Doses of 25 to 75¬†mg daily in the prevention of deficiency, and 250¬†mg or more daily in divided doses for the treatment of deficiency, have been recommended.
Ascorbic acid 100 to 200¬†mg daily may be given with desferrioxamine in the treatment of patients with thalassaemia, to improve the chelating action of desferrioxamine, thereby increasing the excretion of iron. In iron deficiency states ascorbic acid may increase gastrointestinal iron absorption and ascorbic acid or ascorbate salts are therefore included in some oral iron preparations. Ascorbic acid or sodium ascorbate have been used in treating methaemoglobinaemia. Ascorbic acid has been used to acidify urine. It has also been tried in the treatment of many other disorders but there is little evidence of beneficial effect.
Eye drops containing potassium ascorbate have been used for the treatment of chemical burns. Potassium ascorbate 10% is used alternately with sodium citrate 10%; it is believed that the ascorbate works by mopping up free oxygen radicals thus aiding in the prevention of corneal epithelial damage.
Ascorbic acid and calcium and sodium ascorbates are used as antoxidants in pharmaceutical manufacturing and in the food industry.
A beneficial effect of vitamin C therapy has been claimed for an extraordinary number of conditions, including Alzheimer’s disease, atherosclerosis, cancer, the common cold, idiopathic thrombocytopenic purpura, and pre-eclampsia. Other conditions claimed to benefit include asthma, wound healing, psychiatric disorders, infections due to abnormal leucocyte function, infertility, osteogenesis imperfecta, pain in Paget’s disease, and opioid withdrawal. Generally there are few properly controlled studies to substantiate these claims.
Effects on mortality.
There is some suggestion that serum ascorbic acid concentrations are inversely related to all-cause mortality; serum levels were also inversely related to cancer mortality in men but not in women.1-3 However, a meta-analysis of 3 studies found vitamin C supplementation to have no benefit on mortality in elderly people.5
- 1. Loria CM, et al. Vitamin C status and mortality in US adults. Am J Clin Nutr 2000; 72: 139‚Äì45. PubMed
- 2. Simon JA, et al. Relation of serum ascorbic acid to mortality among US adults. J Am Coll Nutr 2001; 20: 255‚Äì63. PubMed
- 3. Khaw K-T, et al. Relation between plasma ascorbic acid and mortality in men and women in EPIC-Norfolk prospective study: a prospective population study. Lancet 2001; 357: 657‚Äì63. PubMed
- 4. Fletcher AE, et al. Antioxidant vitamins and mortality in older persons: findings from the nutrition add-on study to the Medical Research Council Trial of Assessment and Management of Older People in the Community. Am J Clin Nutr 2003; 78: 999‚Äì1010. PubMed
- 5. Ness A, et al. Role of antioxidant vitamins in prevention of cardiovascular diseases. BMJ 1999; 319: 577. PubMed