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This Article Full Text Full Text (PDF) All Versions of this Article: 90/4/1038    most recent ajcn.2009.28190v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Thomson, C. D Articles by Livingstone, V. PubMed PubMed Citation Articles by Thomson, C. D Articles by Livingstone, V. Agricola Articles by Thomson, C. D Articles by Livingstone, V.

Selenium and iodine supplementation: effect on thyroid function of older New Zealanders^1,2,3

¹ From the Departments of Human Nutrition (CDT, JMC, SAS, and JM) and Preventive and Social Medicine (VL), University of Otago, Dunedin, New Zealand.

² Supported by Otago Medical Research Foundation and the University of Otago Research Fund.

³ Address correspondence to CD Thomson, Department of Human Nutrition, University of Otago, PO Box 56, Dunedin, New Zealand. E-mail: christine.thomson{at}otago.ac.nz.

Background: The New Zealand population has both marginal selenium status and mild iodine deficiency. Adequate intakes of iodine and selenium are required for optimal thyroid function.

Objective: The aim of the study was to determine whether low selenium and iodine status compromises thyroid function in an older New Zealand population.

Design: We investigated the effects of selenium and iodine supplementation in a double-blind, randomized, placebo-controlled trial in 100 Dunedin volunteers aged 60–80 y. Participants received 100 µg Se/d as L-selenomethionine, 80 µg I, 100 µg Se + 80 µg I, or placebo for 3 mo. Thyroid-stimulating hormone (TSH), free triiodothyronine (T₃), free thyroxine (T₄), thyroglobulin, plasma selenium, whole-blood glutathione peroxidase (GPx) activity, and urinary iodine concentrations (UICs) were measured.

Results: Plasma selenium (P < 0.0001) and whole-blood GPx activity (P<0.0001) increased from baseline to week 12 in the selenium and selenium plus iodine groups in comparison with the placebo group. Median UIC at baseline was 48 µg/L (interquartile range: 31–79 µg/L), which is indicative of moderate iodine deficiency. UIC increased in the iodine and selenium plus iodine groups and was significant only for the iodine group (P = 0.0014). Thyroglobulin concentration decreased by 24% and 13% of baseline in the iodine and selenium plus iodine groups in comparison with the placebo group (P = 0.009 and P = 0.108, respectively). No significant treatment effects were found for TSH, free T₃, free T₄, or ratio of T₃ to T₄.

Conclusions: Additional selenium improved GPx activity but not the thyroid hormone status of older New Zealanders. Iodine supplementation alleviated the moderate iodine deficiency and reduced elevated thyroglobulin concentrations. No synergistic action of selenium and iodine was observed. The trial was registered at www.anzctr.org.au/registry/ as ACTRN012605000368639.