Colorectal cancer: does it matter if you eat your fruits and vegetables?

Epidemiologists have long regarded vegetables and fruits as key features of a diet associated with a reduced risk of colorectal cancer. In 1997, the American Institute for Cancer Research assembled a panel of leading epidemiologists and basic scientists to review the literature covering the links between all aspects of diet and the causation of all types of cancer. That panel gave its highest rating for degree of scientific certainty to vegetables as a component of diet that would reduce risk of colorectal cancer. For fruits, the evidence is more limited—in fact, the American Institute for Cancer Research panel concluded that no judgment was possible.

In this issue of the Journal, however, Michels et al. report a thoroughly null association between both fruits and vegetables and colorectal cancer risk in a pair of large prospective cohort studies. Their study has several important strengths that make it a valuable contribution to the growing discussion about the role of vegetables and fruits in preventing colorectal cancer. It has the advantages of a prospective study in effectively precluding recall and selection bias. It makes use of data from two separate cohorts, the Nurses' Health Study and the Health Professionals' Follow-up Study, both of which are large and have a substantial number of cases. The article reflects a comprehensive and detailed analysis of the possible association of fruits and vegetables with risk of colorectal cancer.