tailieunhanh - Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 13)

Selenium Selenium, in the form of selenocysteine, is a component of the enzyme glutathione peroxidase, which serves to protect proteins, cell membranes, lipids, and nucleic acids from oxidant molecules. As such, selenium is being actively studied as a chemopreventive agent against certain cancers, such as prostate. Selenocysteine is also found in the deiodinase enzymes, which mediate the deiodination of thyroxine to triiodothyronine (Chap. 335). Rich dietary sources of selenium include seafood, muscle meat, and cereals, although the selenium content of cereal is determined by the soil concentration. . | Chapter 071. Vitamin and Trace Mineral Deficiency and Excess Part 13 Selenium Selenium in the form of selenocysteine is a component of the enzyme glutathione peroxidase which serves to protect proteins cell membranes lipids and nucleic acids from oxidant molecules. As such selenium is being actively studied as a chemopreventive agent against certain cancers such as prostate. Selenocysteine is also found in the deiodinase enzymes which mediate the deiodination of thyroxine to triiodothyronine Chap. 335 . Rich dietary sources of selenium include seafood muscle meat and cereals although the selenium content of cereal is determined by the soil concentration. Countries with low soil concentrations include parts of Scandinavia China and New Zealand. Keshan disease is an endemic cardiomyopathy found in children and young women residing in regions of China where dietary intake of selenium is low 20 gg d . Concomitant deficiencies of iodine and selenium may worsen the clinical manifestations of cretinism. Chronic ingestion of high amounts of selenium leads to selenosis characterized by hair and nail brittleness and loss garlic breath odor skin rash myopathy irritability and other abnormalities of the nervous system. Chromium Chromium potentiates the action of insulin in patients with impaired glucose tolerance presumably by increasing insulin receptor-mediated signaling although its usefulness in treating type II diabetes is uncertain. In addition improvement in blood lipid profiles has been reported in some patients. The usefulness of chromium supplements in muscle building is not substantiated. Rich food sources of chromium include yeast meat and grain products. Chromium in the trivalent state is found in supplements and is largely nontoxic however chromium-6 is a product of stainless steel welding and is a known pulmonary carcinogen as well as a cause of liver kidney and CNS damage. Magnesium See Chap. 346. Fluoride Manganese and Ultratrace Elements An essential function

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