Evaluation of chemical species and bioaccessibility of selenium in dietary supplements

Many kinds of selenium (Se)-enriched supplements are commercially available. To ensure appropriate Se intake, the amount of Se and its chemical species should appear on the bottle or package label. In this study, we verified the Se species and evaluated their potential bioavailability in four commercial Se supplements. The total amounts of Se in all the samples almost coincided with the values indicated on the labels. A hyphenated technique consisting of HPLC and inductively coupled plasma mass spectrometry was used for the speciation of Se in the samples. Although one sample had indicated selenomethionine on its label, it was found to contain solely selenate. Other samples that had selenized yeast (Se-yeast) on their labels mainly contained Se-containing proteins and/or peptides. One Se-yeast sample showed low bioaccessibility (59.71%), in contrast to the two other samples that had around 100% bioaccessibility. The Se supplements actually contained the labeled amount of Se, although some did not contain the Se species indicated on the label and thus were expected to have less Se nutritional availability due to the low bioaccessibility.