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

SeleniumSelenium, 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. ...
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Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 13) Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 13) Selenium Selenium, in the form of selenocysteine, is a component of the enzymeglutathione peroxidase, which serves to protect proteins, cell membranes, lipids,and nucleic acids from oxidant molecules. As such, selenium is being activelystudied as a chemopreventive agent against certain cancers, such as prostate.Selenocysteine is also found in the deiodinase enzymes, which mediate thedeiodination of thyroxine to triiodothyronine (Chap. 335). Rich dietary sources ofselenium include seafood, muscle meat, and cereals, although the selenium contentof cereal is determined by the soil concentration. Countries with low soilconcentrations include parts of Scandinavia, China, and New Zealand. Keshandisease is an endemic cardiomyopathy found in children and young womenresiding in regions of China where dietary intake of selenium is low (manifestations of cretinism. Chronic ingestion of high amounts of selenium leadsto 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 impairedglucose 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. Theusefulness of chromium supplements in muscle building is not substantiated. Richfood sources of chromium include yeast, meat, and grain products. Chromium inthe trivalent state is found in supplements and is largely nontoxic; however,chromium-6 is a product of stainless steel welding and is a known pulmonarycarcinogen, as well as a cause of liver, kidney, and CNS damage. Magnesium See Chap. 346. Fluoride, Manganese, and Ultratrace Elements An essential function for fluoride in humans has not been described,although it is useful for the maintenance of structure in teeth and bone. Adultfluorosis results in mottled and pitted defects in tooth enamel as well as brittlebone (skeletal fluorosis). Manganese and molybdenum deficiencies have been reported in patientswith rare genetic abnormalities and in a few patients receiving prolonged totalparenteral nutrition. Several manganese-specific enzymes have been identified(e.g., manganese superoxide dismutase). Deficiencies of manganese have beenreported to result in bone demineralization, poor growth, ataxia, disturbances incarbohydrate and lipid metabolism, and convulsions. Ultratrace elements are defined as those needed in amounts from alcohol abuse. Cochrane Database Syst Rev CD004033, 2004 Lichtenstein AH, Russell RM: Essential nutrients in a healthy diet: Food orsupplements? JAMA 294:1, 2005 Miller ER et al: Meta-analysis: High-dosage vitamin E supplementationmay increase all-cause mortality. Ann Intern Med 142:37, 2005 [PMID:15537682] Morris MC et al: Dietary folate and vitamin B12 intake and cognitivedecline among community-dwelling older persons. Arch Neurol 62:641, 2005[PMID: 15824266] Murphy SP et al: Multivitamin-multimineral supplements’ effect on totalnutrient intake. Am J Clin Nutr 85(1):280S, 2007 Penniston KL, Tanumihardjo: The acute and chronic toxic effects ofvitamin A. Am J Clin Nutr 83:191, 2006 [PMID: 16469975] Prentice RL: Clinical trials and observational studies to assess the chronicdisease benefits and risks of multivitamin-multimineral supplements. Am J ClinNutr 85(1):308S, 2007 Touvier M et al: Dual association of beta-carotene with risk of tobacco-related cancers in a cohort of French women. J Natl Cancer Inst 97:1338, 2005[PMID: 16174855] Vermeer C et al: Beyond deficiency: Potential benefits of increased intakesof vitamin K for bone and vascular health. Eur J Nutr 43:325, 2004 [PMID:15309455]