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Carcinogens and Anticarcinogens in the Human Diet

Carcinogens and Anticarcinogens in the Human Diet


Preface

Numerous reports, including some from the National Research Council, have examined the relationship of diet to cancer. It is generally accepted that diet is a contributing factor to the onset or progression of some types of cancer and that a prudent s election of foods, including fruits and vegetables, and avoidance or decreased consumption of other foods might influence the risk to an individual of contracting cancer. But can specific chemicals in our diet be identified as causative agents (carcinoge ns) or protective agents (anticarcinogens) for cancer? Some naturally occurring chemicals that are part of our diet have been shown in animal models to cause cancer-and therefore might also serve as potential cancer-causative agents in humans. Almost da ily, the news media report on the presence of one chemical or another that is claimed to be carcinogenic. Many of these are naturally occurring chemicals. The public is bombarded with reports that raise fear and apprehension.

To make a rational estimate of the risk associated with the diet one must know the level of exposure as well as the carcinogenic potency of a suspected chemical. That basic principle of toxicology is sometimes offset by the belief (often associated w ith the Delany amendment) that the presence of a potentially hazardous chemical at even minuscule concentrations is dangerous. In addition, the credibility of such a conclusion often depends on the validity of the test used to identify a specific chemica l as a carcinogen. Many of the data used in this report are based on studies using the rodent bioassay, where tests are carried out at high exposure levels. The ability to relate results obtained using rodent bioassays to the risk for humans-who are exp osed to low levels of a chemical in a complex mixture, such as the diet-is a weakness that puts into question how the results of such evaluations are applied.

This committee has labored diligently and long as it studied, debated, reargued, and wrote the different facets of what some might consider a complex problem that is unsolvable.

As we submit this report we recognize that some readers will look for the identification of a single causative agent to remove from the diet. Others will seek evidence of a panacea-a chemical that will shield them against the causative agents of canc er. Both groups will be disappointed. As the report indicates, we need to know much more than we know today before we can speak with greater certainty about the role of chemicals in the diet as contributors to the burden of cancer in the human populatio n. Such information will come only by continued research, new hypotheses, and a clearer understanding of human biology.

The ability to complete a report of this complexity requires a dedicated staff. We are indebted to efforts and technical expertise of J. David Sandler, project director; Linda V. Leonard, senior project assistant; Carol A. Maczka, program director; G ail Charnley and Richard Thomas (program directors during the early stages of the project); and James J. Reisa, director of the Board on Environmental Studies and Toxicology.

Many distinguished scientists met with the committee and shared their ideas, findings, and interpretations, including: Richard Adamson (National Cancer Institute), Bruce Ames (University of California), Victor Feron (Toxicology and Nutrition Institut e, the Netherlands), Adam Finkel (Resources for the Future), Ronald Hart (National Center for Toxicological Research), Donald Hughes (American Industrial Health Council), Richard Jackson (California Department of Health Services), David Longfellow (Nation al Cancer Institute), Richard Merrill (University of Virginia), Hugh McKinnon (Environmental Protection Agency), Gerard Mulder (Center for Bio-Pharmaceutical Sciences, Sylvius Laboratories, the Netherlands), David Rall, Robert Scheuplein (Food and Drug Ad ministration), Sidney Siegel (National Library of Medicine), and Lee Wattenberg (University of Minnesota). Some of these individuals' affiliations have changed since they provided input to the committee. Our sincere thanks to them for providing guidepos ts that served to mark the path of progress as the committee deliberated specific issues.

Each member of this committee deserves praise and congratulations for his or her wisdom, dedication, perception, and friendship. Although many sessions were exhausting, the high level of interest of each member made this exercise a rewarding and prod uctive experience. Thanks to each and everyone of you for all your good work.

Ronald W. Estabrook
Chairman


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