Vitamin C, a water-soluble
glucose derivative, has considerable
antioxidant activity in vitro, in part because of its ease of oxidation and because the
semidehydroascorbate radical derived from it is of low reactivity.
Vitamin C in vivo is an essential cofactor for a range of
enzymes involved in diverse metabolic pathways, but much recent literature has focused on its
antioxidant effects. Consumption of foods rich in
Vitamin C (fruits and vegetables) is associated with decreased risk of
cardiovascular disease, of many types of
cancer and possibly of
neurodegenerative disease, but the extent to which
Vitamin C contributes to these effects is uncertain. Data using
biomarkers of oxidative damage to
DNA bases have given no compelling evidence to date that ascorbate supplements can decrease the levels of oxidative DNA damage in vivo, except perhaps in subjects with very low
Vitamin C intakes. Similarly, there is no conclusive evidence from studies of strand breaks, micronuclei, or
chromosomal aberrations for a protective effect of
Vitamin C. There is limited evidence that supplements of
Vitamin C might have beneficial effects in disorders of vascular function, and that diet-derived
Vitamin C may decrease
gastric cancer incidence in certain populations, but it is not clear whether it is the
antioxidant or other properties of ascorbate that are responsible for these two actions.