Selenium and iodine supplementation: effect on thyroid function of older New Zealanders.

Study answer

What this study found

Selenium supplementation improved selenium status but did not improve thyroid hormone status, and iodine supplementation improved iodine status and lowered thyroglobulin but did not fully correct mild iodine deficiency over 12 weeks. Plasma selenium increased by week 12 in the selenium-containing groups, with unadjusted increases of 82% for selenium alone and 79% for selenium plus iodine; both were significant versus placebo after adjustment (P < 0.0001). Whole-blood GPx activity also increased with selenium alone by 4.5 U/g (95% CI: 2.7, 6.2) and with selenium plus iodine by 5.2 U/g (95%…

Study & population

Randomized, double-blind trial in noninstitutionalized older adults aged 60 to 80 years living in Dunedin, New Zealand.

Intervention

Participants received oral tablets once daily for 12 weeks: 100 μg selenium as L-selenomethionine, 80 μg iodine, or the combined 100 μg selenium plus 80 μg iodine regimen.

Key limitation

Each active arm was small (n = 25, 25, and 26), and the 12-week duration may have been too short to fully correct iodine deficiency or detect longer-term thyroid effects.

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Original abstract