High doses of multiple antioxidant vitamins: Essential ingredients in improving the efficacy of standard cancer therapy

Numerous articles and several reviews have been published on the role of an tioxidants, and diet and Lifestyle modifications in cancer prevention. Howe ver, the potential role of these factors in the management of human cancer have been largely ignored. Extensive in vitro studies and limited in vivo s tudies have revealed that individual antioxidants such as vitamin A (retino ids), Vitamin E (primarily alpha-tocopheryl succinate), Vitamin C (primaril y sodium ascorbate) and carotenoids (primarily polar carotenoids) induce ce ll differentiation and growth inhibition to various degrees in rodent and h uman cancer cells by complex mechanisms. The proposed mechanisms for these effects include inhibition of protein kinase C activity, prostaglandin E-1- stimulated adenylate cyclase activity, expression of c-myc, H-ras, and a tr anscription factor (E2F), and induction of transforming growth factor-beta and p(21) genes. Furthermore, antioxidant vitamins individually or in combi nation enhance the growth-inhibitory effects of x-irradiation, chemotherape utic agents, hyperthermia, and biological response modifiers on tumor cells , primarily in vitro. These vitamins, individually, also reduce the toxicit y of several standard tumor therapeutic agents on normal cells. Low fat and high fiber diets can further enhance the efficacy of standard cancer thera peutic agents; the proposed mechanisms for these effects include the produc tion of increased levels of butyric acid and binding of potential mutagens in the gastrointestinal tract by high fiber and reduced levels of growth pr omoting agents such as prostaglandins, certain fatty acids and estrogen by low fat. We propose, therefore, a working hypothesis that multiple antioxid ant vitamin supplements together with diet and lifestyle modifications may improve the efficacy of standard and experimental cancer therapies.