NCI dietary guidelines: rationale.

The National Cancer Institute (NCI) believes that the potential for dietary changes to reduce the risk of cancer is considerable and that the existing scientific data provide evidence that is sufficiently consistent to warrant prudent interim dietary guidelines that will promote good health and reduce the risk of some types of cancer. Six interim dietary guidelines and their scientific rationale are discussed herein. The evidence presented for the scientific rationale is based on the 1982 National Academy of Sciences Committee report Diet, Nutrition and Cancer and NCI's own scientific reviews that link long-term dietary patterns with cancer risk. These guidelines to the American public are consistent with other dietary recommendations from the US departments of Agriculture and Health and Human Services, the American Cancer Society, and the American Heart Association.

A critical review of food fiber analysis and data.

Epidemiologists, research scientists, and dietitians need data on the dietary fiber content of foods. This article provides a provisional table on dietary fiber, compiled after a thorough search of the literature and a critical evaluation of the analytical methodology employed. To make fully understandable the limitations and problems associated with the current dietary fiber data base, a short review of what is meant by the term dietary fiber and the complex chemical structures of the major dietary fibers--cellulose, hemicellulose, pectin, and lignin--are presented. A short description of the numerous analytical methods for quantifying dietary fiber, including the neutral detergent fiber procedure, the various enzymatic gravimetric procedures, and the analytic schemes for measuring the major dietary fiber fractions is also given, along with the strengths and weakness of the various procedures. The table on foods commonly eaten in the United States is meant as an interim guide for menu planning and dietary evaluation until newer data become available. Data are most limited on legumes and the numerous specialty baked products and breads available in this country.

Zinc and copper in infant diets.

The diets of 59 healthy Utah infants were examined for nutritional adequacy. The analysis included zinc and copper intake calculated from new assays of zinc and copper in commercial baby foods and table foods obtained at local retail outlets. Group averages showed adequate dietary intake, with copper the limiting nutrient. Zinc-to-copper ratios were only slightly higher than suggested.

Folacin in selected foods.

Representative values for folacin in 299 foods have been developed, based on an extensive literature review. A provisional table of these folacin values has been prepared for foods in 100-gm. portions and for specified weights, representing common household units. The data reflect newer methodology than that used for a prior USDA publication, namely, protection of folacin by ascorbic acid. L. casei is the preferred assay organism. The table includes values for both free and total folacin; however, the authors recommend that, in calculating routine hospital diets, total rather than free folacin be used; this would allow easy and direct comparison with the Recommended Dietary Allowances.

International food component data system.

The International Network of Food Data Systems planning conference recommends establishing nomenclature and a system of coding for use in INFOODS. The International Food Naming System would facilitate collection, tabulation, storing, and retrieval of information. The system consists of two files for each food: one describing the name in a standardized manner and another reporting chemical and biological data. The two files are linked by International Food Number (IFN). Food names consist of controlled terms called facets: origin, part, process, stage of maturity, and grade. Within each facet, such elements as genus, species, variety (scientific name) and generic name, breed or kind, and strain (English name) are defined. Elements are assigned numerical codes to facilitate sorting and storage. Carefully defined standard descriptions are used in each facet. Each descriptor is assigned an alphabetic code, an unlimited number allowing an open-ended flexible system. IFN may be incorporated into a computerized data management system and stored data searched and sorted for information retrieval on given parameters, e.g., country, state, laboratory, or kind of package. Data can be summarized to obtain averages, ranges, and standard deviations. Summarized data, linked with the International Food Names by the IFN, may be printed out in desired format.

The Diet and Cancer Branch, NCI: current projects and future research directions.

Diet, perhaps more than any other environmental factor, has a significant potential for reducing the incidence of cancer. It has been projected that as much as 35 percent of all human cancer can be prevented through effective dietary modification strategies. The comprehensive research program of the DCB significantly directs diet and cancer research toward the ultimate cancer prevention goal of modifying dietary habits of the general population for optimal health. The DCB is currently supporting projects along the entire continuum from laboratory research to human intervention trials: basic research projects in food composition, encompassing dietary fiber, vitamin A and carotenoids and development of INFOODS; physiologic studies establishing safe and effective levels of dietary fiber and carotenoids; modification of eating behavior; human intervention trials of low fat diets in prevention of breast cancer; and clinical nutrition research units.

Clinical trials in cancer prevention.

Research in cancer prevention can be divided into laboratory research, epidemiologic research, and clinical trials. When results from laboratory and/or epidemiologic research support the possibility of clinical cancer prevention, these leads should be subjected to study in clinical trials. If clinical trials produce positive results, wide application of these results to the relevant segments of the general population should then be emphasized. Why are clinical trials needed in cancer prevention? There are several considerations: epidemiologic studies may lack specificity, that is, the ability to reach conclusions that apply to only one specific factor; the predictive value of animal models based on laboratory studies is not entirely known; clinical trials quantitate the level of participant acceptance of the intervention; and clinical trials address the issues of risk/benefit ratios. Over the last 3 years, the National Cancer Institute has supported the development of a program of clinical trials in cancer prevention. The aim of these studies includes the reversal of precursor lesions, prevention of progression from a precursor state to overt malignancy, reduction in the incidence of malignancy, reduction in cancer mortality, and reduction in overall mortality. Interventions under study include a diet with less than 20% of calories from fat, and the administration of single agents or combinations of agents, including beta carotene, vitamin A, 13-cis-retinoic acid, vitamins C, E, and B12, and folacin.