Pro-oxidant activity of vitamin C in drinking water ... - Ã bo Akademi

Review of the literaturejuice daily. It was later found that vitamin C (ascorbic acid) was the active substance in theoranges and lemons that prevented scurvy. With scurvy also came the belief that vitamin Ccould function as an antioxidant protecting against oxidation, as the name ascorbate(antiscorbutic) implies. Vitamin C was first isolated from cabbages, oranges and adrenalglands by Szent-Györgyi in 1928. 15, 17, 181.2. Vitamin C - an important enzymatic cofactorLater it was found that ascorbic acid is a crucial cofactor for many enzymes. Withoutascorbic acid, proline hydroxylase and lysine hydroxylase cannot hydroxylate collagen. 1, 19, 20This leads to reduced formation of collagen fibres, which gives rise to poor wound healingand fragile blood vessels. The collagen fibres strengthen the connective tissues in the bloodvessels, skin, teeth and skeleton. Nowadays, scurvy is a very rare condition, as the quality offood intake has improved, i.e., more fruits and vegetables are consumed. In addition, manyfood products are nowadays fortified with vitamins and vitamin C is a common dietarysupplement. 16Vitamin C is used as cofactor in the synthesis of noradrenaline and carnitine, tyrosinemetabolism and amidation of peptide hormones. 1 In most of these vitamin C-dependentenzymes, vitamin C helps to maintain the enzyme in its active form by keeping the metal(copper and iron) in the active centre in the reduced form. 201.3. Effects of vitamin C supplementationThe body has depots of vitamin C but the vitamin will eventually be depleted. The averageadult has a body pool of 1.0-2.0 grams of vitamin C and the average half-life of vitamin C isabout 10-20 days. 21, 22 Scurvy can be prevented with a vitamin C intake of only 10mg/day. 20A high intake of vitamin C is generally not believed to be harmful since vitamin C is awater-soluble compound that is not stored in the body and the excess ingested vitamin isexcreted in the urine. However, diarrhoea is a directly observable symptom of overconsumptionof vitamin C. 11, 23 The Food and Nutrition Board, Institute of Medicine, hasset 2000 mg as a tolerable upper limit for vitamin C in healthy adults. 10, 118