Diet, Nutrition, and Cancer (1982) / Chapter Skim
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10 Minerals
10 Minerals
Pages 162-201
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From page 162... ...
The carcinogenic action of these elements is difficult to test in animals because some of them are toxic at levels that exceed dietary requirements, and because it is difficult to control synergistic interactions of the element under investigation with other elements that may contaminate air, diet, and drinking water. This chapter contains an evaluation of a few of those trace elements that are nutritionally significant and suspected of playing a role in carcinogenesis.
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From page 163... ...
Epidemiological Evidence Selenium has been reported as having a possible protective effect against cancer. Shamberger and colleagues correlated selenium levels in forage crops (grouped into high, medium, and low categories)
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From page 164... ...
Because studies conducted during the 1940's showed that high levels of selenium induced or enhanced tumor formation, the Food and Drug Administration until recently prohibited the enrichment of animal feeds with selenium, even in areas with established selenium deficiency. In contrast to the results of the earlier investigations, more recent studies by several independent investigators have established that dietary selenium has a protective effect against tumors induced by a variety of chemical carcinogens or at least one viral agent.
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From page 165... ...
A large accumulation of evidence indicates that supplementation of the diet or drinking water with selenium protects against tumors induced by a variety of chemical carcinogens and at least one viral agent (Table 10-1~. Although most investigators found that tumor incidence in the selenium-supplemented animals was approximately one-half that of the control animals, Schrauzer et al.
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From page 167... ...
(1978) stated that the selenium levels in the recipient animals do not influence the fate of transplanted tumor cells; others observed a strong reduction in the growth of inoculated Ehrlich ascites cells in recipient animals injected with high doses of selenium compounds for 3 weeks after the inoculation (Greeder and Milner, 1980~.
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From page 168... ...
The relevance of most of these studies to the risk of cancer for humans is not apparent since the levels of selenium used far exceeded dietary requirements and often bordered on levels that might be toxic. However, one experiment has demonstrated increased susceptibility to DMBA-induced tumors when selenium deficiency was aggravated by high dietary levels of polyunsaturated fatty acids, and protection by a physiological supplement of selenium (0.1 ~g/g)
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From page 169... ...
Epidemiological Evidence There have been few epidemiological studies of the relationship between exposure to zinc and risk of cancer. Stocks and Davies (1964)
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From page 170... ...
They found that levels of zinc in serum and diseased esophageal tissue from esophageal cancer patients were much lower than those in other cancer patients and in normal subjects. Zinc levels in hair were lower in both cancer groups than in normal subjects.
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From page 171... ...
Zinc deficiency appears to retard the growth of transplanted tumors, whereas it enhances the incidence of some chemically induced cancers. In some experiments, dietary zinc exceeding nutritional requirements has been shown to suppress chemically induced tumors in rats and hamsters, but when given in 10-10
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From page 172... ...
IRON Epidemiological Evidence Iron deficiency has been associated with cancers of the upper alimentary tract including the esophagus and stomach. In epidemiological studies conducted in Sweden, iron deficiency was associated with Plummer-Vinson (Paterson-Kelly)
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Summary Epidemiological Evidence. Iron deficiency has been related to an increase in the risk of Plummer-Vinson syndrome, which is associated with upper alimentary tract cancer.
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An increased risk for bronchogenic carcinoma has also been reported for copper miners in cases where exposure to radiation was dismissed as a likely cause (Newman et al., 1976~. Thus, although some data suggest that copper is carcinogenic in humans, very little epidemiological evidence implicates dietary sources per _.
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There is no experimental evidence that the copper levels in animal tissues influence their susceptibility to carcinogens. Summary Epidemiological Evidence.
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From page 176... ...
(1961) compared thyroid cancer mortality rates by state in the United States with corresponding prevalence rates of endemic goiter and found no association between the two diseases.
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From page 177... ...
However, the relationship between iodine and thyroid cancer should be studied further before firm conclusions can be drawn. Epidemiological studies provide no clear evidence that the risk of cancers of the breast, ovary, and endometrium are related to dietary iodine deficiency.
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From page 178... ...
Furthermore, low levels of molybdenum in water supplies have been correlated with excess esophageal cancer mortality in the United States (Berg et _., 1973~. In areas of China at high risk for esophageal cancer, supplementation of the soil with ammonium molybdate has been observed to increase the molybdenum and ascorbic acid content of locally produced grains and vegetables and to decrease their nitrate and nitrite concentration (Luo _ al., 1981~.
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From page 179... ...
Supplementation of molybdenum-deficient soil in high risk areas of China has been observed to increase the ascorbic acid content and lower the nitrate content of locally grown plants and grains, and is therefore being considered as a means of reducing the risk of esophageal cancer. Experimental Evidence.
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From page 180... ...
(1964, 1965) observed no carcinogenic effect in mice given cadmium at 5 mg/liter drinking water, no studies have been conducted in laboratory animals to determine the effect of dietary cadmium on carcinogenicity.
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From page 181... ...
Experimental Evidence. Data from one laboratory experiment suggest that cadmium given in drinking water is not carcinogenic in mice, whereas intramuscular and subcutaneous injections of cadmium salts induce cancer in rats and mice.
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Epidemiological literature on cancer risk associated with occupational, medicinal, and drinking water sources of exposure to arsenic has been reviewed in publications by the International Agency for Research on Cancer (1973, 1980a) and the National Academy of Sciences (1977a,b; 1980a)
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From page 183... ...
Epidemiological Evidence. There is good evidence that drinking water .
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From page 184... ...
correlated the levels of eight trace elements in the water supplies of 10 major river basins in the United States with corresponding cancer mortality rates for white and nonwhite males and females. There were significant correlations for five of the eight elements.
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From page 185... ...
There is very little epidemiological evidence linking dietary lead to the risk of cancer in humans. The only study that correlated lead levels in drinking water supplies and cancer mortality suggested that lead increased the risk of cancer.
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From page 186... ...
186 DIET, NUTRITION, AND CANCER Conclusion On the basis of experiments in animals, it would seem that exposure to large amounts of some compounds of lead may pose a carcinogenic risk to humans. However, there is little direct epidemiological evidence to support this conclusion.
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From page 187... ...
1974. Effect of lead acetate on human leukocyte chromosomes in vitro.
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From page 188... ...
1966. Esophageal cancer in the Bantu of the Transkei associated with mineral deficiency in garden plants.
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1975. The epidemiology of esophageal cancer in north China.
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1978. Zinc deficiency and methylbenzylnitrosamine-induced esophageal cancer in rats.
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From page 191... ...
1980. Factors influencing the inhibitory effect of selenium on mice inoculated with Ehrlich ascites tumor cells.
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From page 192... ...
1981. Enhancement of mammary tumorigenesis by dietary selenium deficiency in rats with a high polyunsaturated fat intake.
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1977. Zinc levels in serum, hair and tumors from patients with esophageal cancer.
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From page 194... ...
A report of the Safe Drinking Water Committee. National Academy Press, Washington, D.C.
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1961. Thyroid cancer and thyrotoxicosis in the United States: Their relation to endemic goiter.
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1978. Trace Elements and Iron in Human Metabolism.
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Associations with dietary intakes and blood levels of certain trace elements, notably Se-antagonists. Bioinorg.
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1965. Intranuclear inclusions and renal tumors in rats fed lead subacetate.
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Toxicology of Trace Elements. Hemisphere Publishing Corporation, Washington and London.
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1981. Epidemiologic and dietary evidence for a specific nutritional predisposition to esophageal cancer.
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From page 201... ...
1980. Research on esophageal cancer in China: A review.
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