Optimization of selenoprotein P and other plasma selenium biomarkers for the assessment of the selenium nutritional requirement: a placebo-controlled, double-blind study of selenomethionine supplementation in selenium-deficient Chinese subjects.
What this study found
Selenium supplementation increased plasma selenoprotein P and identified selenoprotein P as the best biomarker for selenium adequacy. Selenoprotein P was optimized by the 35-bcg Se/day dose, corresponding to a total daily selenium intake of about 49 bcg/d when dietary intake was estimated at 14 bcg/d. Glutathione peroxidase activity was optimized at the 21-bcg Se/day dose, or about 35 bcg/d total intake, while plasma selenium did not show a clear optimization pattern. No important adverse effects were detected.
- Study & population
- This was a placebo-controlled, double-blind, dose-ranging trial in healthy farmers aged 20-50 years from a selenium-deficient area of Mianning County, Sichuan Province, China.
- Intervention
- Healthy selenium-deficient adults were randomized to oral L-selenomethionine once daily for 40 weeks in seven dose groups: 0, 21, 35, 55, 79, 102, or 125 bcg Se/day.
- Key limitation
- The trial was conducted in a relatively small, single rural Chinese population with low baseline selenium intake, which limits generalizability.
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Open PDFOriginal abstract
BACKGROUND The intake of selenium needed for optimal health has not been established. Selenoproteins perform the functions of selenium, and the selenium intake needed for their full expression is not known. OBJECTIVE This study sought to determine the intake of selenium required to optimize plasma selenoprotein P (SEPP1) and to compare SEPP1 with other plasma selenium biomarkers. DESIGN A 40-wk placebo-controlled, double-blind study of selenium repletion was carried out in 98 healthy Chinese subjects who had a daily dietary selenium intake of 14 micro g. Fourteen subjects each were assigned randomly to daily dose groups of 0, 21, 35, 55, 79, 102, and 125 micro g Se as l-selenomethionine. Plasma glutathione peroxidase (GPX) activity, SEPP1, and selenium were measured. A biomarker was considered to be optimized when its value was not different from the mean value of the subjects receiving larger supplements. RESULTS The SEPP1 concentration was optimized at 40 wk by the 35- micro g supplement, which indicated that 49 micro g/d could optimize it. GPX activity was optimized by 21 micro g (total ingestion: 35 micro g/d). The selenium concentration showed no tendency to become optimized. CONCLUSIONS The present results indicate that SEPP1 concentration is the best plasma biomarker studied for assessing optimal expression of all selenoproteins, because its optimization required a larger intake of selenium than did GPX activity. On the basis of the selenium intake needed for SEPP1 optimization with adjustments for body weight and individual variation, ap 75 micro g Se/d as selenomethionine is postulated to allow full expression of selenoproteins in US residents. This trial was registered at clinicaltrials.gov as NCT00428649.