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United States Department of Agriculture

Agricultural Research Service

Title: Determination of selenium bioavailability from wheat mill fractions in rats by using the slope-ratio assay and a modified Torula yeast-based diet

Authors
item Reeves, Phillip
item GREGOIRE, BRIAN
item GARVIN, DAVID
item Hareland, Gary
item Lindlauf, James - UNIV NORTH DAKOTA
item Johnson, Luann - UNIV NORTH DAKOTA
item FINLEY, JOHN

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 2006
Publication Date: January 24, 2007
Repository URL: http://handle.nal.usda.gov/10113/2048
Citation: Reeves, P.G., Gregoire, B.R., Garvin, D.F., Hareland, G.A., Lindlauf, J.E., Johnson, L.K., Finley, J.W. 2007. Determination of selenium bioavailability from wheat mill fractions in rats by using the slope-ratio assay and a modified Torula yeast-based diet. Journal of Agricultural and Food Chemistry. 55:516-522.

Interpretive Summary: Selenium (Se) is an essential nutrient for humans and animals. The Se RDA for adult humans is 55 ug/d; however, dietary amounts as high as 200 ug/d in the highly available form in yeast have been shown to reduce the incidence of certain cancers. Numerous natural foods contain high amounts of Se, but for the most part, it is not known whether this Se can be absorbed and used by the body. This experiment was conducted to determine whether Se could be absorbed efficiently from three mill fractions of wheat: flour, shorts, and bran. To do this, rats were made Se deficient, where their Se-dependent enzymes and the amount of Se in various organs were reduced. Then Se from the wheat fractions was fed to these Se-deficient rats and the enzyme activities and Se concentrations in tissues were measured and compared with those in similar rats fed a highly available form of Se; in this case, sodium selenite or selenomethionine. Then we calculated the percent bioavailability of Se from the wheat fractions relative to that in the highly available form. Results showed that Se from refined wheat flour was nearly 100% available by a number of measures including plasma, liver, kidney, and muscle Se concentrations and liver and blood Se-dependent enzyme activities when compared with similar measures in rats fed NaSelenite or SeMet. However, based on similar criteria, Se from wheat shorts was only about 85% available, and that from wheat bran was about 60% available for absorption. These results indicate that high Se wheat products, particularly those made from refined flour alone might be particularly well suited for use as a dietary Se supplement.

Technical Abstract: Selenium (Se) is an essential mineral micronutrient for animals, and significant evidence supports an association between supra-nutritional Se intake and a reduction in the incidence of some forms of cancer. Thus, supplemental Se intake may provide an avenue for reducing cancer incidence. However, an important issue to consider is the form of Se that should be provided in such a supplement, since the bioavailability and bioactivity of Se can vary dramatically depending on the chemical form in which it is delivered. Because wheat products are the largest source of Se in U.S. diets, the absorption of Se was evaluated in different fractions of milled wheat that exhibits very high Se levels, owing to its production on naturally Se-rich soils. An experiment was conducted to determine the bioavailability of Se from three milled fractions of high-Se wheat. The method used was the slope-ratio assay, which measures the ability of Se from the wheat fractions to regenerate Se-dependent enzyme activities and tissue Se concentrations in Se-deficient rats. The responses generated from wheat Se were compared to a standard response curve generated by feeding graded amounts of Se as sodium selenite (Na2SeO3) or selenomethionine (SeMet) in an AIN-93G -Torula yeast based diet. Results showed that Se availability from wheat flour (~75% extraction) was nearly 100% available by a number of measures including plasma, liver, kidney, and muscle Se concentrations and liver and blood Se-dependent enzyme activities when compared with similar measures in rats fed NaSelenite or SeMet. However, based on similar criteria, Se from wheat shorts was only about 85% available, and that from wheat bran was about 60% available for absorption. These results indicate that high Se wheat products, mainly those made from refined flour alone might be particularly well suited for use as a dietary Se supplement.

Last Modified: 9/10/2014
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