Reflections on the implications of multistage carcinogenesis for the nature of neoplasia

Dietary restriction in animals results in a dramatic reduction of cancer incidence. Several attempts have been made to extrapolate this observation to the human situation. Recent developments in our knowledge of gene–dietary interactions, particularly in relation to vitamins, have been taken into account in a new examination of the likely effects of dietary restriction in humans, but this is a relatively new area of research. Epidemiological studies in relation to diet have also been considered, but probably need to be refined further because of the subtle effects of dietary interactions. Until more detailed information is available the extrapolation can still only be made with the utmost caution.