Family history, metabolic gene polymorphism, diet and risk of colorectal cancer.

Colorectal cancer is thought to be largely due to dietary factors. There is evidence of familial aggregation of colorectal cancer suggesting that genetic susceptibility may be important in the aetiology of the disease. Only limited data are available comparing risk factors for colorectal cancer with and without a family history. There are arguments suggesting that individuals with a first-degree relative with colorectal cancer are at a greater risk from a diet high in energy than individuals without such a family history. Failure to take into account both genetic and environmental factors can lead to bias in the estimation of disease risk. Genetic polymorphisms interact with dietary intake. A number of associations have been observed between specific genetic polymorphisms and colorectal cancer. But there are inconsistencies between studies, because of methodological limitations in initial studies. Different effects of dietary factors on colorectal cancer risk among individuals with different genotypes or of different effects of a genotype on colorectal cancer risk among individuals with different exposures need to be addressed in future works.