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Do Iodine and Selenium Work Together?
Selenium and iodine both matter for thyroid hormones; selenium deficiency could make iodine deficiency worse, and the adult upper limit for selenium is 400 mcg a day.[1]
Based on NIH Office of Dietary Supplements — Selenium fact sheet · Updated October 10, 2026
Selenium and iodine both matter for thyroid hormones[1]
Selenoproteins take part in thyroid hormone metabolism, and selenium deficiency may make the effects of iodine deficiency worse.
Selenium deficiency could make iodine deficiency worse. The adult upper limit for selenium is 400 mcg a day, from food and supplements.
Source [1]Selenium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. (ods.od.nih.gov)
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- Does Tryptophan Turn Into Niacin?Yes. The body makes niacin from tryptophan: 60 mg of tryptophan counts as 1 mg of niacin.
Sources
- Selenium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
This page is general information from the cited sources, not medical advice. If you take prescription medication, are pregnant, or manage a health condition, check supplement changes with a pharmacist or doctor.