Bile Acids: Promoters or Carcinogens in Colon Cancer?

Since the 1970s it has been generally considered that bile acids are promoters of colon cancer, but lack carcinogenic activity. However, recent evidence indicates that bile acids do, indeed, act as carcinogens. Substantial evidence from a variety of sources indicates that bile acids are involved in the etiology of colon cancer, although it has usually been assumed that they only act as promoters. The incidence of colon cancer, as well as mortality rate, varies dramatically across regions of the world. There is more than a 10-fold difference in incidence of colon cancer between countries [1,2]. Rates of colon cancer incidence among populations migrating from low-incidence to high-incidence countries change rapidly, and within one generation reach the rate in the highincidence country. This could be seen, for instance, in a population migrating from Japan to Hawaii [3]. These changes in colon cancer incidence are thought to be largely due to changes in diet. There is a correlation between large increases in both meat and fat in the diet and large increases in incidence of colon cancer, graphed on an exponential scale.