Colorectal cancer is the fourth most common cancer in the world today (WHO 1997). Its incidence rates vary approximately 20-fold around the world so that the high-risk areas include North America, Europe, and Australia, whereas Central and South America, Asia, and Africa are areas of low risk. In Finland, cancer of the colon and the rectum are the second and third most common cancers in women and men respectively (Finnish Cancer Registry 2000). The number of new cases per year has steadily increased since 1965, being now three times higher than in the mid 1960s. The incidence rates of colon cancer are currently increasing in all industrialised countries as well as in the urban areas of developing countries (WHO 1997).

The 20-fold international difference in colon cancer rates is generally explained by differences in dietary habits and other environmental factors. In their much referred report, Doll and Peto (1981) estimated that dietary factors may account for approximately 35% of cancer deaths, although the range of their estimate was wide from as low as 10% to as high as 70%. Since the early 1980s, a large body of evidence has emerged from epidemiological studies concerning the relationship between diet and colon cancer, which was recently reviewed by the expert panel of the World Cancer Research Fund (1997). The expert panel concluded that the most effective way of preventing colorectal cancer is consumption of diets high in vegetables and low in red and processed meat. Furthermore, consumption of diets high in non-starch polysaccharides (fibre), starch and carotenoids and low in fat, sugar, and eggs possibly decreases the risk of colon cancer (World Cancer Research Fund 1997).