title: Review: When is an antioxidant not an antioxidant? A review of novel actions and reactions of vitamin C.
abstract: Vitamin C (or ascorbic acid) is regarded as the most important water-soluble antioxidant in human plasma and mammalian cells which have mechanisms to recycle and accumulate it against a concentration gradient, suggesting that the vitamin might also have important intracellular functions. In this review we summarize evidence from human trials that have attempted an association between vitamin C supplementation and an effect on biomarkers of oxidative DNA damage. Most studies reviewed herein showed either a vitamin C-mediated reduction in oxidative DNA damage or a null effect, whereas only a few studies showed an increase in specific base lesions. We also address the possible beneficial effects of vitamin C supplementation for the prevention of cancer and cardiovascular disease. Finally, we discuss the contribution of cell culture studies to our understanding of the mode of action of vitamin C and we review recent evidence that vitamin C is able to modulate gene expression and cellular function, with a particular interest in cell differentiation.
authors.affiliation: Pharmaceutical Sciences Research Division, Kings College London University.
authors.forename: Tiago L
authors.initials: TL
authors.lastname: Duarte
authors.forename: Joseph
authors.initials: J
authors.lastname: Lunec
mesh_terms: D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000378:metabolism* / Q000494:pharmacology*; D004249:DNA Damage; D019587:Dietary Supplements; D015870:Gene Expression; D006801:Humans; D016877:Oxidants / Q000378:metabolism / Q000494:pharmacology; D018384:Oxidative Stress; D015398:Signal Transduction / Q000502:physiology
chemical_list: D000975:Antioxidants; D016877:Oxidants; D001205:Ascorbic Acid