Environmental and other risk factors for colorectal carcinogenesis

Diet plays a role in the risk of colon cancer, but exactly how it affects risk is unknown. In western countries diet is low in fibre and high in animal protein, fats and refined carbohydrates such as sugar. Risk seems to be reduced by a diet high in calcium, vitamin D and vegetables such as Brussels sprouts, cabbage and broccoli. Familial polyposis has been studied sufficiently and increases the risk of colon cancer. Moreover, in relatives there is frequently a familial history of an increased incidence of colorectal cancer. There is no conclusive evidence to support any of the hypotheses proposed to explain the role of dietary factors in colorectal carcinogenesis. Prospective trials should generate the information required to develop strategies for diet modification to reduce the incidence of colorectal carcinoma. There is hope that this understanding will lead to a variety of dietary, medical, hormonal and molecular interventions to reduce disease incidence and improve the prognosis of patients with cancers of the colon and rectum.