Excess vitamin B6 promotes colon cancer - Adequate intake of folate, methionine, riboflavin, and vitamin B-6 may prevent aberrant DNA methylation and thereby protect against colorectal cancer (CRC)...methionine was associated with decreased risk of proximal colon cancer among men and rectal cancer among women...Riboflavin tended to be associated with decreased proximal colon cancer risk among women...This is the 2nd prospective cohort study in which vitamin B-6 intake was associated with increased risk of rectal tumors in women...

High fat dairy reduces colon cancer risk, especially CLAs

TEA HELPS PREVENT COLON CANCER

"Research shows that epigallocatechin-3-gallate (EGCG), an antioxidative polyphenol in tea, can inhibit the activity of the §-catenin/Tcf signaling pathway in vitro. More than 80% of human colon cancers have a mutation in the APC gene, and those that do not have mutations in §-catenin. "

CALCIUM REDUCES COLON CANCER: http://www.ajcn.org/cgi/content/abstract/80/5/1358

Conclusion: High calcium intake, particularly from supplements, is associated with a reduced risk of distal colorectal adenoma.

Science 25 March 2005 Cancers of the Gut and Western Ills Ian T. Johnson* 

In their well-known 1981 review on the causes of cancer in the United States, Doll and Peto* estimated that around one-third of deaths from cancer could be attributed to diet and were therefore, in principle, preventable. Epidemiological evidence continues to support this general conclusion, but in contrast to cardiovascular disease, for which the link to nutrition is now generally recognized, the relationship between diet and cancer has made much less impact on both policy-makers and the general public. One reason for this is the absence of any single hypothesis on which to build a dietary strategy for cancer prevention; this itself is a reflection of the complexity of human diets and the obvious fact that cancer is not a single disease. Although there has been huge progress in our understanding of the molecular basis of many cancers in recent years, most of the new knowledge has been deployed in the search for new therapies rather than to understand the role of nutrition in their causation. Nevertheless, the mechanisms linking diet to cancer can be understood and exploited for prevention as much as for treatment, and there are sound scientific and strategic reasons to focus such research on carcinomas of the alimentary tract.

Inhibition of carcinogenesis by polyphenols: evidence from laboratory investigations

 Joshua D Lambert et al Am. J. Clinical Nutrition,  Jan 2005;  81:  284S - 291S.

“For example, compounds such as curcumin are effective when applied topically to the skin or administered orally to affect the colon but are not effective in internal organs such as the lungs.”