Editing Malignant transformation (section)

===Diet and colon cancer===

Colon cancer provides one example of the mechanisms by which diet, the top factor listed in the table, is an external factor in cancer.  The Western diet of African Americans in the United States is associated with a yearly colon cancer rate of 65 per 100,000 individuals, while the high fiber/low fat diet of rural Native Africans in South Africa is associated with a yearly colon cancer rate of <5 per 100,000.<ref name="O'Keefe2015">{{cite journal |vauthors=O'Keefe SJ, Li JV, Lahti L, Ou J, Carbonero F, Mohammed K, Posma JM, Kinross J, Wahl E, Ruder E, Vipperla K, Naidoo V, Mtshali L, Tims S, Puylaert PG, DeLany J, Krasinskas A, Benefiel AC, Kaseb HO, Newton K, Nicholson JK, de Vos WM, Gaskins HR, Zoetendal EG |title=Fat, fibre and cancer risk in African Americans and rural Africans |journal=Nat Commun |volume=6 |pages=6342 |year=2015 |pmid=25919227 |pmc=4415091 |doi=10.1038/ncomms7342 |bibcode=2015NatCo...6.6342O }}</ref>  Feeding the Western diet for two weeks to Native Africans increased their secondary bile acids, including carcinogenic [[deoxycholic acid]],<ref name=Bernstein2011>{{cite journal |vauthors=Bernstein C, Holubec H, Bhattacharyya AK, Nguyen H, Payne CM, Zaitlin B, Bernstein H |title=Carcinogenicity of deoxycholate, a secondary bile acid |journal=Arch. Toxicol. |volume=85 |issue=8 |pages=863–71 |year=2011 |pmid=21267546 |pmc=3149672 |doi=10.1007/s00204-011-0648-7 }}</ref> by 400%, and also changed the colonic microbiota.<ref name="O'Keefe2015" />  Evidence reviewed by Sun and Kato<ref name=SunKato>{{cite journal |vauthors=Sun J, Kato I |title=Gut microbiota, inflammation and colorectal cancer |journal=Genes & Diseases|volume=3 |issue=2 |pages=130–143 |year=2016 |pmid=28078319 |doi=10.1016/j.gendis.2016.03.004 |pmc=5221561}}</ref> indicates that differences in human colonic microbiota play an important role in the progression of colon cancer.