Halliwell B
Department of Biochemistry, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore, Singapore.
Mutat Res. 2001 Apr 18;475(1-2):29-35. doi: 10.1016/s0027-5107(01)00072-0.
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.
维生素C是一种水溶性葡萄糖衍生物，在体外具有相当强的抗氧化活性，部分原因在于其易于氧化，且由此衍生的半脱氢抗坏血酸自由基反应活性较低。体内的维生素C是一系列参与多种代谢途径的酶的必需辅助因子，但最近的许多文献都集中在其抗氧化作用上。食用富含维生素C的食物（水果和蔬菜）与心血管疾病、多种癌症以及可能的神经退行性疾病风险降低有关，但维生素C对这些影响的贡献程度尚不确定。迄今为止，使用DNA碱基氧化损伤生物标志物的数据并未提供令人信服的证据表明，除了维生素C摄入量极低的受试者外，补充抗坏血酸能降低体内氧化DNA损伤的水平。同样，关于链断裂、微核或染色体畸变的研究也没有确凿证据表明维生素C具有保护作用。有有限的证据表明，补充维生素C可能对血管功能紊乱有益，且饮食中摄入的维生素C可能会降低某些人群患胃癌的几率，但目前尚不清楚是抗坏血酸的抗氧化特性还是其他特性导致了这两种作用。
