Long-term supplementation with selenate and selenomethionine: urinary excretion by New Zealand women.
Thirty-six New Zealand women aged between 18 and 23 years received daily for 32 weeks, 200 micrograms Se as Se-enriched yeast (selenomethionine, SeMet), or brewer's yeast mixed with selenate, or no added Se (placebo) in a double-blind trial. Mean daily Se excretion increased with both supplements; the selenate group excreted more than the SeMet group, 123 v. 66 micrograms/d respectively at week 2, equivalent to 57 v. 27% of the dose. Thereafter Se output increased for the SeMet group reaching a plateau at about 100 micrograms/d at week 16, when plasma Se had also plateaued at 190 ng/ml. The selenate group had reached an earlier plateau of 110 ng Se/ml at week 7. There was a close relationship between 24 h urine and plasma Se for the SeMet group but not for the selenate group. Renal plasma clearances showed two distinctly different responses; the clearance of 0.4 ml/min reached by the SeMet group at week 2 plateaued as plasma Se increased almost 2-fold; whereas for the selenate group the clearance varied between 0.8 and 1.1 ml/min whilst plasma Se remained almost constant at 110 ng/ml. Previous studies, also of 200 micrograms Se/d as Se-rich bread, in New Zealand (NZ) and elsewhere showed similar responses to Se-yeast; the selenite response was intermediate between selenate and Se-yeast (SeMet). The full significance of these studies awaits identification of Se components in plasma, glomerular filtrate and urine; meanwhile renal clearances serve as a pointer to changes in the distribution of Se-containing fractions in the plasma. Trimethylselenonium was detected in basal urines, and was a minor component in urines of supplemented NZ subjects at about 1% of the total Se.
Robinson
M F
MF
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Thomson
C D
CD
Jenkinson
C P
CP
Luzhen
G
G
Whanger
P D
PD
D000293:Adolescent; D000328:Adult; D004311:Double-Blind Method; D005260:Female; D005527:Food, Fortified; D006801:Humans; D008657:Metabolic Clearance Rate; D064586:Selenic Acid; D012643:Selenium / Q000097:blood / Q000652:urine*; D018036:Selenium Compounds / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000652:urine; D012645:Selenomethionine / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013997:Time Factors
D018036:Selenium Compounds; D012645:Selenomethionine; D012643:Selenium; D064586:Selenic Acid; C003717:trimethylselenonium