Diet, nutrition, and cancer.

Evidence pertaining to the role of dietary factors in carcinogenesis comes from both epidemiological studies and laboratory experiments. In 1982, the Committee on Diet, Nutrition, and Cancer of the National Research Council conducted a comprehensive evaluation of this evidence. That assessment as well as recent epidemiological and laboratory investigations suggest that a high fat diet is associated with increased susceptibility to cancer of different sites, particularly the breast and colon, and to a lesser extent, the prostate. Current data permit no definitive conclusions about other dietary macroconstituents including cholesterol, total caloric intake, protein, carbohydrates and total dietary fiber. Specific components of fiber, however, may have a protective effect against colon cancer. In epidemiological studies, frequent consumption of certain fruits and vegetables, especially citrus fruits and carotene-rich and cruciferous vegetables, is associated with a lower incidence of cancers at various sites. The specific components responsible for these effects are not clearly identified, although the epidemiological evidence appears to be most consistent for a protective effect of carotene on lung cancer and less so for vitamins A and C and various cancer sites. The laboratory evidence is most consistent for vitamin A deficiency and enhanced tumorigenesis, and for the ability of various nonnutritive components in cruciferous vegetables to block in-vivo carcinogenesis. The data for minerals and carcinogenesis are extremely limited, although preliminary evidence from both epidemiological and laboratory studies suggests that selenium may protect against overall cancer risk. Frequent consumption of cured, pickled, or smoked foods, possibly because they may contain nitrosamines or polycyclic aromatic hydrocarbons, appears to increase the risk of esophageal or stomach cancer, however, the specific causative agents in these foods are not clearly identified. Excessive alcohol consumption among smokers appears to be associated with an elevated risk of cancers of the oral cavity, esophagus, larynx, and respiratory tract. The mechanisms of action of dietary factors on carcinogenesis are poorly understood. The NRC committee, and more recently, the National Cancer Institute and the American Cancer Society have proposed interim dietary guidelines to lower the risk of cancer. These guidelines are consistent with general dietary recommendations proposed by U.S. government agencies for maintenance of good health.(ABSTRACT TRUNCATED AT 400 WORDS)