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Page 192
Colon cancer studies show that selenium works by inhibiting lipid peroxidation. Selenium has been found to decrease the binding of various chemical carcinogens to DNA. This process takes place in the membranes of the liver and kidney where enzymes function as drug metabolizers. 48
Selenium's main function in the body is to convert hydrogen peroxide to water, which is important for cellular health. Blood levels of this trace mineral are usually depressed in cancer patients. The cancer prevention component of the National Cancer Institute has compiled information showing that there are fewer cancer deaths in areas containing high levels of selenium in the soil than in areas with low levels of this important trace mineral.
Epidemiological studies show that high selenium intake is associated with a reduction in tumors at various sites, including mammary tissue. Numerous studies also document the ability of dietary selenium to reduce the incidence and total number of tumors induced by a variety of carcinogens. The ability of selenium to alter the metabolism of some carcinogens (including the mammary carcinogen DMBA) indicates that this trace element can be effective in inhibiting the initiation phase of carcinogens. Alterations in DMBA-DNA adducts resulting from dietary selenium supplementation were found to correlate with final tumor incidence and tumor number. Although the mechanism is unknown, several lines of evidence also point to the ability of selenium to effectively inhibit the promotional stage of carcinogenesis. Selenium supplements are also effective in depressing the incidence of vitally induced mammary tumors. The efficacy by which selenium inhibits chemically induced, vitally induced, and transplantable tumors makes it a unique dietary nutrient.
The December 1996 issue of the Journal of the American Medical Association reported the results of a clinical trial in which half the subjects received 200 mcg of selenium-containing yeast per day along with their normal diets, and the other half received normal diets only. The results are quite striking: the incidence of cancers of the lung, colon, and prostate were more than 50 percent lower among those taking the selenium-containing yeast.49
A study done with rats that were given the mammary carcinogen DMBA concluded that administration of the dietary supplement selenium in the form of sodium selenite markedly decreased the binding of DMBA to mammary cell DNA. Increasing the dietary content of selenium resulted in a proportional decrease in the binding of DMBA to DNA.50

 
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