[Vitamins and cancers]

To a great extent carcinogenesis depends on the environment. Some vitamins contribute to the "exogenous" protection against aggressors (i.e., on a molecular scale, active forms of oxygen and free radicals). Epidemiology provides numerous data in favour of this protection, but these date are sometimes ambiguous or contradictory. Current, active experimental studies will probably lead to firm conclusions within the next few years. As regards vitamin A, considerable advances have been made in fundamental research (we now know its molecular mechanism of action, notably on genes) and in applied research (differentiation of leukaemic cells). In various aspects vitamin D resembles vitamin A and also acts on the haematopoietic tissue. Vitamin E is difficult to study, but its protective effect on cell membranes and structures cannot be questioned. Vitamin C emerges from a period of controversy and is increasingly studied at present: it might be a useful adjuvant for the treatment of cancers.