Selenium supplementation affects the retention of stable isotopes of selenium in human subjects consuming diets low in selenium

Twenty-nine women and fifteen men from an area of low Se intake (South Isla nd of New Zealand) consumed 100 mu g stable Se-74, as selenate given in wat er after an overnight fast, and blood was collected for 3 weeks. They were then divided into five groups and supplemented with 0, 10, 20, 30 and 40 mu g Se/d (as selenomethionine) for 5 months. After 5 months, they received a second dose of Se-74 identical to the first. Supplementation significantly altered retention of Se-74 in the plasma, but not in the erythrocytes or p latelets. Subjects receiving the placebo retained the greatest amount, and subjects receiving 30 mu g supplemental Se/d retained the least Se-74. Supp lementation resulted in relatively more isotope being retained in a medium molecular mass protein considered to be albumin, and relatively less in ano ther fraction considered to be selenoprotein P. The lack of many observed c hanges in retention of stable Se, and the shift in retention among the plas ma proteins, suggests that supplemental Se was not being used to replete cr itical pools of Se, probably because of adaptation to low Se intake.