In Canada, colorectal cancer (CRC) is the second leading cause of death due to cancer among men and the third leading cause of death due to cancer among women. In 2004, about 11900 men and 8800 women would have been diagnosed as new cases of CRC.1 Diet has long been thought to have a role in the etiology of CRC, particularly when a poor diet is combined with excess calorie intake and weight gain, physical inactivity, and unhealthy practices, such as smoking and consuming a great deal of alcohol.

Current knowledge about food consumption patterns indicates that a diet high in vegetables, fruit, and fibre is protective against certain types of cancer, but the evidence that fruit and vegetable consumption is specifically related to a reduced risk of CRC was recently challenged. In an attempt to clarify the relationship between diet and CRC, researchers are examining individual dietary components, such as red meat, fibre, folic acid, calcium, and vitamin D. Some studies have focused on adenomas, precursors to CRC, or analysis of colon and rectal cancer, both separately and together.

Bidoli et al found that high intake of refined starches, eggs, cheese, and red meat increased risk of CRC. Risk of colon or rectal cancer was about twice as great among those who consumed these foods more frequently. On the other hand, more frequent consumption of tomatoes was associated with a 50% and 60% reduction in risk of colon cancer and rectal cancer, respectively. A study of CRC among people residing in northern Italy revealed that 17% of CRC cases were attributable to consumption of red meat.

Dietary fibre varies considerably in its physical properties and chemical composition, but can be classified according to its water solubility. This affects its action in the body and might be relevant to the issue of risk of CRC. Bran fibre is insoluble; fruit and vegetable fibre tends to be more soluble.

Terry et al examined fruit, vegetable, and fibre intake and risk of CRC among Swedish women known for their low consumption of fruit and vegetables and their high consumption of cereals. High consumption of fruit was associated with a 32% reduction in risk of CRC, while high intake of cereal fibre did not lower risk of CRC.

The observation that folic acid supplementation was associated with a substantial decrease in colon cancer among ulcerative colitis patients led researchers to examine the role of folic acid in prevention of CRC25.

Calcium and vitamin D are thought to reduce risk of CRC through mechanisms that decrease cell proliferation or promote cell differentiation. In general, cohort studies have found that milk and dairy products have a protective effect on CRC, but case-control studies do not support this relationship.

Thanks and Regards,
Michelle
Managing Editor
Colorectal Cancer: Open Access