Selenium is a nutritionally essential element, but it is also one of the most toxic essential elements when exposure is excessive.
Barring exogenous contamination (which is frequent for Selenium), hair Selenium levels accurately reflect tissue levels. Hair is subject to considerable Selenium contamination by some antidandruff shampoos.
Elevated hair Selenium is almost always from external contamination. One exposure to a Selenium containing anti-dandruff shampoo will elevate the Selenium levels.
Similarly, sulfur containing shampoos are often contaminated with Selenium and can also cause artifactually high hair Selenium levels.
Selenium toxicity usually results from industrial exposure. Se is utilized in the electronics and related industries.
Selenium is utilized in xerography, semiconductors, photoelectric cells and infrared optic materials. Selenium is also utilized in the manufacture of pink and red glasses, and for head-resistant red pigments in plastics, enamels, paints and inks.
Selenium can be toxic when ingested at levels exceeding 15 times that needed for essential functions.
Selenium toxicity (selenosis) can result in: interference with the metabolism of sulfur-bearing amino acids, structural changes and red pigmentation in hair and nails, garlic breath, metallic taste in the mouth, discoloration of teeth and skin, gastroenteritis, and neurological disorders. Some Selenium compounds have been reported to have carcinogenic activity and promote the carcinogenic effects of certain chemicals.
Confirmatory tests for Selenium excess are measurements of Selenium level in whole blood or packed red blood cells.
Selenium (Se) is normally found in hair at very low levels, and several studies provide evidence that low hair Se is reflective of dietary intake and associated with cardiovascular disorders. Utilization of hair Se levels to assess nutritional status, however, is complicated by the fact that use of Se- or sulfur-containing shampoo markedly increases hair Se (externally) and can give a false high value.
Se is an extremely important essential element due to its antioxidative function as an obligatory component of the enzyme glutathione peroxidase. Se is also protective in its capacity to bind and ”inactivate” mercury, and Se is an essential cofactor in the deiodination of T-4 to active T-3 (thyroid hormone). Some conditions of functional hypothyroidism therefore may be due to Se deficiency (Nature; 349:438-440, 1991); this is of particular concern with mercury exposure. Studies have also indicated significant inverse correlations between Se and heart disease, cancer, and asthma.
Selenium deficiency is common and can result from low dietary intake of Se or vitamin E, and exposure to toxic metals, pesticides/herbicides and chemical solvents.
Symptoms of Se deficiency are similar to that of vitamin E deficiency and include muscle aches, increased inflammatory response, loss of body weight, alopecia, listlessness, skeletal and muscular degeneration, growth stunting, and depressed immune function.
Confirmatory tests for Se deficiency are Se content of packed red blood cells, and activity of glutathione peroxidase in red blood cells.
Selenium is normally found in hair at very low levels, and several studies provide evidence that low hair Selenium is reflective of dietary intake and associated with cardiovascular disorders. Utilization of hair Selenium levels to assess nutritional status, however, is complicated by the fact that use of Selenium- or sulfur-containing shampoo markedly increases hair Selenium (externally) and can give a false high value.
Selenium
