Absorption of selenium

Occupational studies indicate that humans absorb elemental selenium dusts and other selenium compounds, but quantitative inhalation toxicokinetic studies in humans have not been done. Studies in dogs and rats indicate that following inhalation exposure, the rate and extent of absorption vary with the chemical form of selenium. Studies in humans and experimental animals indicate that, when ingested, several selenium compounds including selenite, selenate, and selenomethionine are readily absorbed, often to greater than 80% of the administered dose. Although a study of humans did not detect evidence of dermal absorption of selenomethionine, one study of mice indicates selenomethionine can be absorbed dermally. There is little or no information available on the absorption of selenium sulfides, but selenium disulfides are not believed to be absorbed through intact skin. 

Studies using dogs and rats indicate that absorption of selenium following inhalation exposure is extensive, although the rate of absorption depends on the chemical form of selenium. In rats (Medinsky et al. 1981a) and dogs (Weissman et al. 1983), the absorption of selenium following inhalation exposure... 

A comparison of absorption of selenium by selenium-depleted rats after oral administration of sodium selenate, selenomethionine, or methyl selenocysteine (from high-selenium broccoli) found that gross absorption of selenium from methyl selenocysteine was significantly lower (85%) than from sodium selenate or selenomethionine (91%), further, true selenium absorption adjusted for urinary excretion was significantly different for methyl selenocysteine, sodium selenate, and selenomethionine, with the lowest absorption for methyl selenocysteine and the highest for selenomethionine (Finley 1998). Absorption of selenium from selenomethionine was not significantly lower than from sodium selenate. 

Dermal absorption was tested in eight women at a maximum dose of 0.0029 mg selenium/kg as selenomethionine (0.05% L-selenomethionine in a lotion). No detectable increase in serum selenium concentrations was observed but because the concentrations tested were so low, absorption cannot be ruled out (Burke et al. 1992a). Absorption of selenium disulfide was examined using a monthly 24-hour urine specimen in 16 persons who washed their hair weekly with a 1% selenium disulfide shampoo. No differences were found from control urinary selenium levels over the 1-year exposure period (Cummins and Kimura 1971). No absorption of selenium from selenium sulfide was seen in 15 persons who applied a 2.5% selenium sulfide suspension to their torsos and allowed it to remain on the body overnight (Kalivas 1993). 

Cretins or other individuals with iodine or thyroid deficiencies may be more sensitive to adverse health effects from selenium exposure (Contempre et al. 1991b, 1992). Iodine supplementation of these individuals without selenium supplementation may further exacerbate the effects. The elderly may be less susceptible to the negative effects of selenium and more prone to selenium deficiencies. A number of researchers have reported lower absorption of selenium and lower selenium tissue concentrations in the elderly compared to younger adults (Martin et al. 1991 Morisi et al. 1989). 

Solomons NW, Torun B, Janghorbani M, et al. 1986. Absorption of selenium from milk protein and isolated soy protein formulas. J Pediatr Gastroenterol Nutr 5 122-126. 

Although chronic toxicity due to inhalation or absorption of selenium is usually seen only in industry, cases of chronic poisoning in seleniferous areas (for instance, the Enshi region in China) have been studied and attributed to consumption of food contaminated with selenium (NAS 1976, Glover et al. 1979, Newland 1982, Olson 1986, Einbrodt and Michels 1984, WHO... 

Christensen. M.J., Janghorbani, M., Steinke, F.H., Istfan, N.W. and Young, V.R. (1984). Simultaneous determination of absorption of selenium from poultry meat and selenite in young men application of a triple stable isotope method. Br. J. Nutr. 52, 443. 

Silver and mercury were shown to markedly reduce the absorption of selenium in rats when the inorganic salts of these elements were given orally (Whanger, 1976). Cadmium had a lesser effect on selenium absorption, and lead had no effect. Using lettuce leaves labeled either intrinsically or extrinsically with and Se, the absorption of Se... 

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