This is the first of three articles on food and risk of colorectal cancer (CRC). Links to the other 2 articles at the end.

Dietary consumption of fruits and vegetables has been suggested as a general recommendation for promotion of better health for many reasons, including cardiovascular benefit. ^1-3 A high consumption of fruits and vegetables has also been suggested as a possible way to decrease the risk of colorectal cancer (CRC), however previous studies have not been consistent in demonstrating benefit. In a 2007 study of 756,217 men and women, the consumption of fruits and vegetables was not found to be strongly associated with colon cancer risk, although the data did show a lower risk of distal colon cancer.² A 2009 study by van Duihnhoven and colleagues examines the relationship between self-reported consumption of fruits and vegetables and the incidence of CRC.³

The European Prospective Investigation into Cancer and Nutrition studied 452,755 patients (70% women). The participants completed a dietary questionnaire from 1992-2000 and they were followed for cancer incidence and mortality until 2006. Most of the participants were recruited from the general population residing in Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden and the United Kingdom. Data were measured by country-specific validated dietary assessment methods designed to capture local dietary habits and to promote high compliance with the study.  The researchers were interested in the following main food groups: all fruits and vegetables combined, all vegetables, and all fruit.

Study results 

• Both men and women with higher consumption of fruit and vegetables were slightly older, shorter, lower in weight, had lower intakes of meat and higher intake of fish and total fiber, less likely to be smokers and more physically active
• Men with higher levels of consumption of fruit and vegetables reported higher cereal fiber intake
• Fruits and vegetables combined cohort: data showed an inverse association with CRC and colon cancer, but not with rectal cancer;
  • Subgroup analysis by smoking status showed a decreasing trend for CRC and colon cancer in never and former smokers with an increasing trend for risk of rectal cancer for current smokers
• All vegetables cohort: no evidence of an inverse association between vegetable consumption and CRC;
  • Similar association between smokers was noted, with mild smokers showing a smaller risk of CRC than heavy smokers
• All fruit cohort: no association between fruit consumption and CRC, colon or rectal cancer was observed;
  • No associations noted in the different subgroups of smoking status or with alcohol
• Red or processed meat modified the association with both fruit and vegetables and all fruit cohort
• Alcohol did not affect the association between total fruit and vegetable intake and risk of CRC

The authors of the study concluded  

• The association between vegetables and CRC risk were larger for heavy smokers and recent quitters than for mild smokers and long-term quitters, suggesting that smoking may negate the potential benefit of vegetables on CRC. Larger studies are needed to confirm this data.
•  Consumption of vegetables alone did not show a statistically significant association with CRC risk, a weak inverse association of fruit and vegetable consumption was seen with colon, but not rectal cancer, suggesting that these tumors may have different etiologies and thus behave differently in terms of diet and risk.

Consumption of fruits and vegetables have been suggested as a means for improving general health, however more data are needed to confirm the association between a fruit and vegetable diet and reduction in the risk of colorectal cancer.

For another view of Diet, Nutrition and Cancer link to: http://www.medscape.com/viewarticle/701722?src=mpnews&spon=7&uac=41299PY 

References

1. Kerver JM, Yang EJ, Bianchi L, et al. Dietary patterns associated with risk factors for cardiovascular disease in healthy US adults.  Am J Clin Nutr. 2003;78:1103-10. Abstract is available here: http://www.ajcn.org/cgi/content/abstract/78/6/1103
2. Koushik A, Hunter DJ, Spiegelman D, et al. Fruits, vegetables, and colon cancer risk in a pooled analysis of 14 cohort studies. J Natl Cancer Inst. 2007;99:1471-83. Free pdf text available here: http://jnci.oxfordjournals.org/cgi/reprint/99/19/1471
3. Van Duijnhoven FJB, Bueno-De-Mesquita HB, Ferrari P, et al. Fruits, vegetables, and colorectal cancer risk: the European Prospective Investigation into Cancer and Nutrition. Am J Clin Nutr. 2009;89:1-12. Abstract is available here: http://www.ajcn.org/cgi/content/abstract/89/5/1441

Link to article #2 - Dietary Animal Fat or Animal Protein and Risk of CRC.   http://www.managecrc.com/Articles/ArticleReader.aspx?article=151&page=1 

Link to article #3 - Cooking Meat and Fish at High Temperatures May Increase The Risk of Colorectal Adenomas. http://www.managecrc.com/Articles/ArticleReader.aspx?article=109&page=1