Hughes D A
Diet, Health and Consumer Science Division, Institute of Food Research, Norwich Research Park, UK.
Proc Nutr Soc. 1999 Aug;58(3):713-8. doi: 10.1017/s0029665199000932.
Many epidemiological studies have shown an association between diets rich in carotenoids and a reduced incidence of many forms of cancer, and it has been suggested that the antioxidant properties of these compounds are a causative factor. Attention has focused on the potential role of one specific carotenoid, beta-carotene, in preventing cancer, and numerous publications have described in vitro experiments and animal studies which suggest that not only can this carotenoid protect against the development of cancer, but also several other chronic diseases. Since the immune system plays a major role in cancer prevention, it has been suggested that beta-carotene may enhance immune cell function. Several human trials, using dietary beta-carotene supplementation with a wide range of intakes, have been undertaken to address this hypothesis. The general conclusion of these studies is that this compound can enhance cell-mediated immune responses, particularly in the elderly. The present article will review some of these human studies and, hopefully, complement the reviews of other authors associated with the present symposium, some of whom will also describe work in this area. Potential mechanisms for the effects of carotenoids on immune function will also be reviewed. Finally, possible reasons for the failure of three major prospective studies to demonstrate a beneficial effect of beta-carotene supplementation on lung cancer risk will be discussed.
许多流行病学研究表明，富含类胡萝卜素的饮食与多种癌症发病率的降低之间存在关联，并且有人提出这些化合物的抗氧化特性是一个致病因素。人们将注意力集中在一种特定的类胡萝卜素——β-胡萝卜素在预防癌症方面的潜在作用上，大量出版物描述了体外实验和动物研究，这些研究表明这种类胡萝卜素不仅可以预防癌症的发生，还可以预防其他几种慢性疾病。由于免疫系统在癌症预防中起主要作用，因此有人提出β-胡萝卜素可能会增强免疫细胞功能。已经进行了几项人体试验，采用不同摄入量的膳食补充β-胡萝卜素，以验证这一假设。这些研究的总体结论是，这种化合物可以增强细胞介导的免疫反应，尤其是在老年人中。本文将回顾其中一些人体研究，希望能补充本次研讨会其他作者的综述，他们中的一些人也将描述该领域的工作。还将综述类胡萝卜素对免疫功能影响的潜在机制。最后，将讨论三项主要前瞻性研究未能证明补充β-胡萝卜素对肺癌风险有有益影响的可能原因。
