Previous studies on CRC have often failed to distinguish between the different sites of origin of cancers in the large bowel, even though it is now well established that tumors in the proximal colon develop along different pathways to those of the distal colon and rectum and that risk of cancer varies by subsite within the colorectum. The mechanisms for different effects of dietary components on different sites of the large bowel have not yet been determined.
The authors conclude that "from a public health point of view it is easier to translate food-based analyses into dietary recommendations, rather than using the intake of single nutrient."
The article is "Fruit and vegetable consumption and the risk of proximal colon, distal colon and rectal cancers in a case-control study in Western Australia" by Neeltje Annema, Jane S. Heyworth, Sarah A. McNaughton, Barry Iacopetta, and Lin Fritschi. It appears in the Journal of the American Dietetic Association, Volume 111, Issue 10 (October 2011) published by Elsevier.
Source: Journal of the American Dietetic Association