Cooke M S, Evans M D, Mistry N, Lunec J
Oxidative Stress Group, Division of Chemical Pathology, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, University Hospitals of Leicester NHS Trust, Leicester LE2 7LX, UK.
Nutr Res Rev. 2002 Jun;15(1):19-42. doi: 10.1079/NRR200132.
Epidemiological evidence consistently shows that diets high in fresh fruit and vegetables significantly lower cancer risk. Given the postulated role of oxidative DNA damage in carcinogenesis, the assumption has been made that it is the antioxidant properties of food constituents, such as vitamin C, E and carotenoids, which confer protection. However, epidemiological studies with specific antioxidants, either singly or in combination, have not, on the whole, supported this hypothesis. In contrast, studies examining the in vitro effect of antioxidants upon oxidative DNA damage have generally been supportive, in terms of preventing damage induction. The same, however, cannot be said for the in vivo intervention studies where overall the results have been equivocal. Nevertheless, recent work has suggested that some dietary antioxidants may confer protective properties through a novel mechanism, unrelated to their conventional free-radical scavenging abilities. Upregulation of antioxidant defence, xenobiotic metabolism, or DNA-repair genes may all limit cellular damage and hence promote maintenance of cell integrity. However, until further work has clarified whether dietary supplementation with antioxidants confers a reduced risk of cancer and the mechanism by which this effect is exerted, the recommendation for a diet rich in fruit and vegetables remains valid empirically.
流行病学证据始终表明，富含新鲜水果和蔬菜的饮食能显著降低患癌风险。鉴于氧化DNA损伤在致癌过程中的假定作用，人们认为是食物成分（如维生素C、E和类胡萝卜素）的抗氧化特性起到了保护作用。然而，总体而言，对特定抗氧化剂单独或联合进行的流行病学研究并未支持这一假设。相比之下，研究抗氧化剂对氧化DNA损伤的体外作用时，在预防损伤诱导方面通常是支持这一观点的。然而，体内干预研究的情况并非如此，总体结果并不明确。尽管如此，最近的研究表明，一些膳食抗氧化剂可能通过一种新机制发挥保护作用，这与其传统的自由基清除能力无关。抗氧化防御、外源性物质代谢或DNA修复基因的上调都可能限制细胞损伤，从而促进细胞完整性的维持。然而，在进一步研究明确膳食补充抗氧化剂是否能降低患癌风险以及这种作用的机制之前，基于经验，富含水果和蔬菜的饮食建议仍然有效。
