Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 2, 1999
Publication Date: N/A
Interpretive Summary: Selenium is an essential nutrient, and the National Research Council has set a Recommended Dietary Allowance (RDA) of 70 ug/day for adult men. However, some people do not consume this much Se, especially people in geographically isolated areas such as Finland and New Zealand, and it is important to know if Se supplements would be beneficial to such people. This study used people living on the South Island of New Zealand as a model for people consuming less Se than the RDA, and the purpose of the experiment was to determine if supplemental Se altered their metabolism of Se. This was studied by giving all subjects a test dose of a stable isotope of Se, supplementing the people for 5 months with Se, and then giving the test isotope dose again. If supplemental Se decreased the body's demand for Se, then retention of the isotope should be less the second time. This occurred in plasma, i.e. less stable Se was retained the second time, but it did not occur for red blood cells and platelets. Plasma is the body pool that takes up Se most quickly, red cells and platelets take a much longer time. Therefore these results suggest that supplemental Se consumed by this group of subjects did cause a physiological change in plasma (and the degree of change was related to the amount of supplemental Se), but not in red cells or platelets. Whether this change is good or bad will depend on the results of future studies.
Technical Abstract: A series of experiments was conducted by using stable isotopes of selenium (Se) in healthy men and women living in an area of low Se intake. The first experiment studied the kinetics of stable isotope retention in blood fractions and utilized 10 subjects who ingested 100 ug of 74Se. The second examined the effect of supplemental Se on retention of stable Se; 41 subjects (who had been screened to assure low Se status) were fed 100 ug of 74Se. After 10 days of blood collection, they were divided into five groups and supplemented with 0, 10, 20, 30 and 40 ug Se/day (as selenomethionine) for 5 months. After five months, they received a second dose of 74Se identical to the first. For both experiments, maximal retention of the isotope in plasma was between 6 and 12 hours post-dosing. Retention in erythrocytes was biphasic; there was an initial peak around 4 hours which declined by 24 hours; isotope retention then began to increase e again and continued to increase until the end of the study (14 days post- dosing). Retention in platelets was maximal after about 10 days. Supplementation significantly altered retention of 74Se in the plasma, but not in the erythrocytes or platelets. Subjects receiving the placebo retained the greatest amount, and subjects receiving supplemental Se of 30 ug/d retained the least. Women retained significantly more 74Se in the platelets in the first experiment, and tended to return more 74Se in the erythrocytes in the second study. These data suggest that supplementing Se to subjects in low Se status alters retention of Se in plasma, which is indicative of short-term status, but not in pools indicative of long-term Se status (erythrocytes and platelets).