Diet, Nutrition, and Cancer Directions for Research (1983) / Chapter Skim
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7. Vitamins, Minerals, and Nonnutritive Inhibitors and Carcinogenesis
7. Vitamins, Minerals, and Nonnutritive Inhibitors and Carcinogenesis
Pages 36-46
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From page 36... ...
Evidence relating these and other microconstituents to carcinogenesis was discussed in Chapters 9, 10, and 15 of the committee's first report (National Research Council, 1982~. Data relating other microconstituents (e.g., the B vitamins)
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From page 37... ...
present in fruits and vegetables were found to inhibit carcinogenesis. The specific agents responsible for the lower cancer incidence observed in populations that frequently consumed fruits and carotene-containing vegetables have not been identified (National Research Council, 1982, Chapter 9~.
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From page 38... ...
Because minerals function in very fundarnental biochemical processe s, including immune reactions, detoxif ication, and free-radical trapping, it is reasonable to postulate that they may influence mechanisms that affect the development of cancer. On the other hand, although there is an adequate understanding of the mechanisms and sites of the physiological action of the trace elements iron, iodine, zinc, copper, chromium, and selenium, there is no precise knowledge of the mechanisms that might be involved in their effects on carcinogenesis.
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From page 39... ...
For example, large amounts of vitamin C greatly increase the bioavailability of iron compound s, while simultaneously reducing selenite to the biologically unavailable elemental selenium (Monsen et al., 1978; Newberry and Christian, 1965~. High but not excessive supplements of certain trace elements, although not necessarily toxic by themselves, can interfere with the metabolism of other elements to create secondary deficiencies Levander and Cheng, 1980)
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From page 40... ...
One study suggests that selenium-deficient diets increase the risk of cancer, compared to diets containing nutritionally adequate but not excessive levels (Ip and Sinha, 1981~. Because of the relatively narrow range between toxic and optimum levels of selenium (National Research Council, 1980a)
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From page 41... ...
NONNUTRITIVE INHIBITORS OF CARCINOGENESIS An increasing number of nonnutritive substances in food have been found to inhibit carcinogenesis in laboratory animals. Included among these substances are phenols, indoles, aromatic isothiocyanates, methylated flavones, protease inhibitors, and plant sterols (National Research Council, 1982, Chapter 15~.
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From page 42... ...
Current technology makes it feasible to identify dietary compounds that can inhibit neoplasia during the promotion phase. For example, there are three biochemical events that are associated with some facets of tumor promotion in laboratory animals.
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From page 43... ...
· When justified by sufficiently definitive data from experimental and/or epidemiological investigations, intervention studies with these microconstituents or with foods rich in these substances should be considered (see Chapter 4~. O Techniques should be developed for detecting dietary compounds that have the capacity to inhibit carcinogenesis.
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From page 44... ...
o Epidemiological studies should be conducted to assess more directly the possible inhibitory effect s of vitamin C on the induction of gastric cancer and possibly cancer of other sites in the gastrointestinal tract, e.g., the colorectum. Vi tamin E o S tudies should be conducted in laboratory animals to determine the effects of vitamin E on chemically induced neoplasia of the large bowel and the breast.
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From page 45... ...
· Studies in humans should be conducted under close medical supervision to monitor the metabolic effects of different forms of selenium supplements used in moderate amounts. · Ultimately, consideration should be given to intervention studies in countries known to have inadequate selenium intakes, e.g., China, New Zealand, and Finland.
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From page 46... ...
· Studies should be conducted in animals to determine the conditions under which these compounds will inhibit carcinogenesis and to identify characteristics that are related to their potential for preventing neoplasia. Their mechani sms of inhibition and their adverse effects, if any, also need to be identified.
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