Bioavailability of selenium

The bioavailability of selenium to a benthic deposit-feeding bivalve, Macoma balthica from particulate and dissolved phases was determined from AE data. The selenium concentration in the animals collected from San Francisco Bay was very close to that predicted by a model based on the laboratory AE studies of radiolabelled selenium from both particulate and solute sources. Uptake was found to be largely derived from particulate material [93]. The selenium occurs as selenite in the dissolved phase, and is taken up linearly with concentration. However, the particle-associated selenium as organoselenium and even elemental selenium is accumulated at much higher levels. The efficiency of uptake from the sediment of particulate radiolabelled selenium was 22%. This contrasts with an absorption efficiency of ca. 86% of organoselenium when this was fed as diatoms - the major food source of the clam. The experiments demonstrated the importance of particles in the uptake of pollutants and their transfer through the food web to molluscs, but the mode of assimilation was not discussed. 

Hemken, R.W. and Jacques, K.A. 1998. Bioavailability of selenium yeast (Sel-Plex) vs sodium selenite for dairy cattle. Proceedings of the 6th International Symposium on the Uses of Selenium and Tellurium, Selenium-Tellurium Development Association, May 10-12, 1998, Scottsdale, AZ, USA. pp 161-162. 

Levander, O.A., Alfthan, G., Arvilommi, H., Gref, C.G., Huttunen, J.K., Kataja, M., Koivistoinen, P., and Pikkarainen, J. 1983. Bioavailability of selenium in Finnish men as assessed by glutathione peroxidase activity and other blood parameters. Am. J. Clin. Nutr. 37, 887-897. 

E. H. Larsen, M. Hansen, H. Paulin, S. Moesgaard, M. Reid, M. Rayman, Speciation and bioavailability of selenium in yeast-based intervention agents used in cancer chemoprevention studies, J. AO AC lnt., 87 (2004), 225 D 232. 

Although geology is the primary control on the selenium concentration of sod, the bioavailability of selenium to plants and animals is determined by other factors including pH and redox conditions, speciation, soil texture and mineralogy, organic matter content, and the... 

The iron oxide and clay content of soils and sediments can affect the bioavailability of selenium markedly. The strong pH dependence of adsorption is an important control. Maximum adsorption occurs between pH 3 and pH 5 and decreases as the pH rises. Organic matter also removes selenium from soil solution, possibly as a result of the formation of organometallic complexes. Addition of PO4 to soils increases selenium uptake by plants, because the PO ion displaces selenite from soil particles making it more bioavailable. Conversely, increasing the concentrations of PO4 in soils can... 

The study concluded that when the bioavailability of selenium is low, any factor that further reduces its bioavailability and mobility may be critical. Adding selenium fertilizer to crops rather than to soils was recommended to increase the selenium concentrations in local diets. No cases of KD have been reported since 1996, as the diet has become more diversified as a result of improvements in economic conditions and transport. 

Morris JG. 1988. The bioavailability of selenium in animal foods. In Tanji KK, Valoppi L, Woodring RC, eds. Selenium contents in animal and human food crops grown in California. Cooperative Extension University of California, Division of Agriculture and Natural Resources. Publication 3330, 89-96. 

RNSRUD R and Lorentzen M (2002) Bioavailability of selenium from raw or cured selenomethionine-enriched fillets of Atlantic salmon (Salmo solar) assessed in selenium deficient rats. 

Luten J.B., Lorentzen, M., Sieling, F. W., van Aken-Schneyder, P., Hoek, M., Kotterman, M.J.J., van Dael, P., and Fairweather-Tait, S.J. (2004) Bioavailability of selenium from fish, yeast and selenate a comparative study in humans using stable isotopes. Eur. 

Thiry C., Ruttens A., De Temmerman L., Schneider Y.-J., Pussemier L. Current knowledge in species-related bioavailability of selenium in... 

Amweg EL, Stuart DL, Weston DP (2003) Comparative bioavailability of selenium to aquatic organisms after biological treatment of agricultuial drainage water. Aquat Toxicol 63 13-25... 

Combs GF, Combs SB (1986) The role of selenium in nutrition. Academic, Orlando, p 535 Combs GF, Garbisu C, Yee BC, Yee A, Carlson DE, Smith NR, Magyarosy AC, Leighton T, Buchanan BB (1996) Bioavailability of selenium accumulated by selenitereducing bacteria. Biol Trace Elem Res 52 209-225... 

Whanger PD, Ip C, Polan CE, Uden PC and Welbaum G. 2000. Tumorigenesis, metabolism, speciation, bioavailability, and tissue deposition of selenium in selenium-enriched ramps (Allium tricoccum). J Agric Food Chem 48(11) 5723-5730. 

Luoma, S.N., Johns, C., Fisher, N.S., Steinberg, N.S., Oremland, R.S., and Reinfelder, J.R. (1992) Determination of selenium bioavailability to a benthic bivalve from particulate and solute pathways. Environ. Sci. Technol. 26, 485 192. 

J. Cases, I. A. Wysocka, B. Caporiccio, N. Jouy, P. Besangon, J. Szpunar, J. Rouanet, Assessment of selenium bioavailability from high-selenium spirulina subfractions in selenium-deficient rats, J. Agric. Food Chem., 50 (2002), 3867-3873. 

C. Thomas, I. Buth, H. Waldner, Bioavailability investigations of selenium from foods and supplements after enzymatic digestion using HPLC-ICP-MS with hexapole collision cell. Poster presentation at the II. International Conference on Trace... 

Bioavailabilitv of methvlmercurv in food. Measurements of absorption and toxicity have generally been made using aqueous solutions of methylmercury. The absorption and bioavailability of methylmercury in food, specifically fish and bread, may be affected by dietary components. Potential confounders that may affect bioavailability of methylmercury are dietary phytate and other dietary fibrous materials found in bread and the complexation of methylmercury with selenium in fish. 

Selenium is a naturally occurring mineral element in the earth s crust. It is distributed widely in nature and is found in most rocks and soils at concentrations between 0.1 and 2.0 ppm. However, selenium is seldom found in its elemental form in the environment, but is obtained primarily as a byproduct of copper refining. Selenium exists in several allotropic forms. The primary factor determining the fate of selenium in the environment is its oxidation state. Selenium is stable in four valence states (-2, 0, +4, and +6) and forms chemical compounds similar to those of sulfur. The heavy metal selenide compounds (-2) are insoluble in water, as is elemental selenium. The inorganic alkali selenites (+4) and selenates (+6) are soluble in water and are, therefore, more bioavailable. 

Elemental selenium (selenium[0]) is rarely found naturally, but it is stable in soils. Selenates (selenium[+6]) and selenites (selenium[+4]) are water soluble and can be found in water. Sodium selenate is among the most mobile forms of selenium because of its high solubility and inability to adsorb to soil particles. More insoluble forms, such as elemental selenium, are less mobile therefore, there is less risk for exposure. Because of greater bioavailability, water-soluble selenium compounds are probably more lethal than elemental selenium by any route. Selenium is found in nature complexed with multiple compounds, and although various forms are discussed in the profile, many others exist. Plants can contain organic selenium in the form of the amino acids selenomethionine and selenocysteine, along with the dimethyl selenides. Elemental selenium can be oxidized to form selenium dioxide. While the products of oxidation might be expected at the soil surface, elemental selenium would be the expected predominant form in deep soils where anaerobic conditions exist. Selenium sulfides, used in some antidandruff shampoos, are not very water soluble and, therefore, like elemental selenium are relatively immobile in the environment. 

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