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 Island of New Zealand) consumed 100 mu g stable Se-74, as selenate given in water 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 platelets. Subjects receiving the placebo retained the greatest amount, and subjects receiving 30 mu g supplemental Se/d retained the least Se-74. Supplementation resulted in relatively more isotope being retained in a medium molecular mass protein considered to be albumin, and relatively less in another fraction considered to be selenoprotein P. The lack of many observed changes in retention of stable Se, and the shift in retention among the plasma proteins, suggests that supplemental Se was not being used to replete critical pools of Se, probably because of adaptation to low Se intake.