Factors influencing the carcinogenicity of food chemicals

The relationship between food and cancer is extremely complex. It is generally accepted that diet is a contributory factor in the aetiology of a large proportion of cancers, but with very few exceptions, we are unable to identify specific causal agents. Many food components have genotoxic potential and more are produced endogenously during digestion. Conversely, there is increasing evidence that consumption of some foods may decrease the risk of cancer, and a number of plant constituents have been shown to have the potential to inhibit various stages of the carcinogenic process. Yet we have little understanding of the interactions between the different food-related genotoxic and protective factors. A further complication is the variation in individual susceptibility and vulnerability. As a result we are still not able to determine the optimal diet for minimising cancer risk. In recognition of these issues, the UK Ministry of Agriculture, Fisheries and Food (MAFF) is funding a number of projects aimed at providing greater mechanistic understanding of the links between food and cancer, in order to offer detailed advice to the public. This report summarises the proceedings of a workshop entitled 'Factors influencing the carcinogenicity of food chemicals', held in London on 1 June 1998, providing overviews of some of the key issues, and demonstrating how the MAFF-funded research is contributing to advances in these areas. It includes discussion of genetic polymorphisms and how they may contribute to individual susceptibility and help to identify causal links between food components and colorectal cancer. Biomarkers of DNA damage in human studies and of inhibition of carcinogen activation and endogenous formation of genotoxic reactive nitrogen species are examined. Also considered are the potential uses of physiologically based pharmacokinetic modelling techniques for providing more accurate estimates of risk and reducing the uncertainty in extrapolation between species and doses. Research now in progress will help to establish the critical risk and protective factors involved in diet-related colorectal cancers, in order to provide a sound scientific basis for formulation of dietary advice to the public.