Bioavailability of selenium to Finnish men as assessed by platelet glutathione peroxidase activity and other blood parameters

Abstract

Three groups of 10 men of low selenium status were given 200 micrograms Se/day as Serich wheat, Se-rich yeast, or sodium selenate for 11 wk. Twenty unsupplemented subjects served as controls. Plasma Se levels increased steadily in the wheat and yeast groups for 11 wk without plateauing, whereas in the selenate group, plasma Se plateaued around 110 ng/ml after 4 wk. Platelet glutathione peroxidase (GSH-Px) activities increased rapidly in the wheat and selenate groups for 4 wk and then plateaued. Platelet GSH-Px increased more slowly in the yeast group. Ten weeks after the supplements were discontinued, platelet GSH-Px was higher in the wheat and yeast groups than in the selenate group. Assessment of Se bioavailability requires a short-term platelet GSH-Px measurement to determine immediate availability, a medium-term plasma Se measurement to estimate retention, and a long-term platelet GSH-Px measurement after supplements are discontinued to determine the covertibility of tissue Se stores to biologically active Se.

Plasma selenoprotein P levels of healthy males in different selenium status after oral supplementation with different forms of selenium

“…The Figure 1 Changes in selenoprotein P levels in plasma from healthy Finnish men that had received different forms of selenium supplements (200 mg selenium/d) in two previous studies, Trial l in 1981±1982 (Levander et al, 1983) and Trial II in 1987 (Alfthan et al, 1991). In Trial II the subjects had acquired a higher selenium status through a nation-wide selenium supplementation of fertilisers starting in 1985.…”

“…The mean selenoprotein P level of the placebo group stayed constant throughout the supplementation period, but in the postsupplementation period it increased by 21% from 11±21 weeks (P`0.05). The most plausible explanation of this phenomenon is that selenium-rich grain was imported during this period and the selenium intake of the subjects was increased accordingly (Levander et al, 1983;Mutanen & Koivistoinen, 1983), although unknown factors may also be involved.…”

“…As described in previous reports (Levander et al, 1983;Alfthan et al, 1991) the study group consisted of healthy Finnish men, aged 36±60 y. Fifty men were recruited for the ®rst supplementation study during 1981±1982 (Trial I) and the same subjects except ®ve also participated in the second study (Trial II) six years later, when they were divided into the same supplementation groups as before. The mean daily dietary intake of selenium of adults increased from approximately 40 mg in 1981 to 100 mg in 1987 as a result of the country-wide supplementation of fertilisers with selenium starting in Finland in 1985 (Aro et al, 1997).…”

“…Data on plasma and erythrocyte selenium, and plasma and platelet glutathione peroxidase activity were available from previous studies (Levander et al, 1983;Alfthan et al, 1991).…”

“…Design: The same study group participated in two similar selenium supplementation trials, Trial I in 1981(Levander et al, 1983 and Trial II in 1987(Alfthan et al, 1991. During Trial II the mean baseline intake of selenium in Finland was higher compared to that during Trial I (100 and 40 mg/d, respectively), due to a nationwide supplementation of fertilisers which started in 1985.…”