Iodine
Potassium iodide / kelp · Foundation
Essential for thyroid hormone, and one of the few nutrients where too much causes the same disease as too little.
What the evidence says
Deficiency is the leading preventable cause of intellectual disability worldwide, and iodised salt is one of public health's great successes. In iodine-replete countries frank deficiency is uncommon, though pregnancy raises requirements. Supplementing beyond need does not improve thyroid function.
What studies used
Requirements sit near 150 mcg/day, higher in pregnancy; the tolerable upper limit is 1,100 mcg. Published studies had not established a preferred timing.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- Excess iodine causes both hyperthyroidism and hypothyroidism, and can trigger thyroiditis in susceptible people — the U-shaped curve is real
- Kelp products are the usual route to accidental megadoses; their content varies enormously and is often unlabelled
Evidence base
established literature
Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.
This letter measures how much human research exists, not whether it works for you — the tier above (Strong) is the read on quality.
Research (12)
- Thyroid-Gut-Axis: How Does the Microbiota Influence Thyroid Function?Nutrients · 2020
- Effect of selenium on thyroid autoimmunity and regulatory T cells in patients with Hashimoto's thyroiditis: A prospective randomized-controlled trialClin Transl Sci · 2021
- Iodine excessBest Pract Res Clin Endocrinol Metab · 2010
- Smoking and thyroidClin Endocrinol (Oxf) · 2013
- Selenium and thyroidBest Pract Res Clin Endocrinol Metab · 2009
- Pregnancy and iodineThyroid · 2001
- [Iodine and thyroid autoimmunity]Z Arztl Fortbild Qualitatssich · 2004
- GoiterCurr Probl Surg · 1969
- Iodine and thyroid autoimmune disease in animal modelsThyroid · 2001
- Over-the-counter-drug-induced thyroid disordersEndocr Pract · 2013
- Iodine excess and thyroid autoimmunityJ Endocrinol Invest · 2003
- Correlation between iodine intake and thyroid disorders: a cross-sectional study from the South of ChinaBiol Trace Elem Res · 2014
Turn Iodine into a plan that's yours
The info above is free. Membership makes it personal, the Coach answers questions about your exact stack, the Stack tracks it for you, and the Verified Sources shows you how to vet what you buy.
- ✓ AI Coach, ask anything about your stack. It does the dosing math, flags interactions, and tells you what to do next.
- ✓ Personal Stack, save your protocol, track it across devices, log doses, get a heads-up before a vial runs out.
- ✓ Verified Sources, the vetted reference for checking quality and sourcing, members only.
Cancel anytime · or save with $59.99/yr · Coach + Stack included