Cancer and cardiovascular disease remain the primary causes of death in western countries.Colorectal carcinoma (CRC) is among the most prevalent neoplasms in western countries, and 11 million cancers newly develop yearly worldwide, which result in seven million deaths. Predictions for 2030 foresee an incidence twice as high. CRC is the third most common type of cancer with nearly a million new cases per year, and the fourth leading cause of death.In our country it is the second leading cancer after lung cancer in males and breast cancer in females. Incidence in Spain is estimated in some 25,000 diagnosed cases per year with mortality around 50%, which means that approximately 12,500 patients die annually from CRC in our country; it therefore represents the second leading cause of cancer-related death nationwide (1).Most CRC cases (70-75%) are sporadic forms whose triggering factors are still unknown; the remaining 25-30% of patients may have a family history favorable to the development of this neoplasm. Thus in 3-5% of cases CRC develops in the setting of a disease with known hereditary background, primarily familial adenomatous polyposis (FAP), with a prevalence of 1%, or as hereditary non-polyposis CRC (HNPCC) or Lynch syndrome, with a prevalence around 2.5% in Spain. Less than 1% CRCs develops in patients with inflammatory bowel disease.Marked regional differences exist, and areas with a high socioeconomic status are most affected -northern Europe, USA and Australia. In these countries the incidence of CRC is four times higher than in developing countries, which ranges from over 40 cases per 100,000 population in Europe to fewer than 5 cases per 100,000 population in Africa or Central America. These incidence rates seem consistent with a country's urban drift-it is estimated that most CRC cases will be diagnosed in economically developed regions by 2030. Observational studies have shown that the incidence of CRC among immigrants from low-risk countries to high-risk countries matches the letters' incidence within one or two generations. Environmental factors play thus a clear key role in the development of CRC.Therefore, temporal studies and studies in migratory populations suggest that CRC greatly depends on environmental factors, as shown by the highly variable frequencies seen among different countries, and the marked increases in case numbers seen in populations migrating from low-incidence to high-incidence areas. Based on these epidemiological studies, it has been estimated that up to 70-80% of CRCs may be attributed to the actions of dietary, environmental, and lifestyle factors. This suggests the relevance of potentially modifiable causes that could be prevented to a great extent (2-5).