Dietary factors for cancer of specific sites.

Even though the issues have been greatly simplified in this article by citing of only the most salient data, when a number of different cancers are examined, a diverse range of dietary factors is implicated. For a number of cancers, very little is known, and for others, competing hypotheses are supported by conflicting data. Despite these obvious limits, some generalizations regarding common patterns of risk at different cancer sites may be possible. For example, although the nutrients and mechanisms may vary by site, lack of consumption of fruits and vegetables has been linked repeatedly to cancers of the mouth, larynx, esophagus, and lung. A similar association is suggested for cancers of the cervix and bladder. Another commonality is the association of dietary fat with cancers of the breast, ovary, prostate, and, possibly, colon. Alcohol is associated with cancers of the mouth, larynx, and, possibly, rectum. Coffee has been studied in association with cancers of the pancreas, ovaries, and lungs, but few of these studies have been replicated and the role of this common dietary exposure remains in question. In most other instances, unique cancers are linked to unique dietary exposures, for example, fiber and colorectal cancer or nitrates and stomach cancer. Given that both common and unique sources of dietary risk may be identified for different cancers, future research may benefit from a two-pronged research strategy. Basic nutrients need to be examined for multiple cancers, and specific aspects of diet require in-depth study for specific cancers. From such an approach, it may be possible to resolve some of the questions and issues reviewed herein.