Iodine + Selenium Protocol

📜 Historical Use

Iodine is the rare supplement whose history is a public-health programme rather than a folk tradition. Before iodization, deficiency was endemic in the mountainous regions of the United States and Mexico and in what was known as the goiter belt around the Great Lakes. ODS records that US salt manufacturers have been adding iodine to table salt since the 1920s, and notes that the practice is still voluntary - iodized salt is a convention, not a mandate, which is why ODS lists non-users of iodized salt among the groups at risk of inadequate intake. The approach was exported: roughly 88% of households worldwide now use iodized salt, although insufficiency persists in some regions. Seaweed is the older dietary route and remains the least predictable one. ODS reports that commercially available seaweeds in whole or sheet form have iodine concentrations ranging from 16 mcg/g to 2,984 mcg/g - a spread of nearly 200-fold, which makes any kelp-based dose an estimate rather than a measurement. Modern supplements use potassium iodide or sodium iodide, or kelp; many multivitamin and mineral products contain iodine at 150 mcg, matching the adult RDA rather than the larger amounts marketed for thyroid protocols.

📊 What the Research Shows

The two halves of this protocol rest on very different evidence. Iodine sufficiency is among the best established public-health findings in nutrition: ODS calls iodine deficiency the most common cause of preventable intellectual disability in the world, and reports that salt iodization programs have dramatically reduced its prevalence worldwide. Equally important for a US reader, ODS states that overt iodine deficiency is now uncommon in North America - so the premise that a typical American reader needs supplemental iodine is not one the federal source grants. The selenium half is where the page overreaches. ODS summarises a systematic review of 16 trials in which selenium at 80-200 mcg/day lowered TPO antibody levels in levothyroxine-treated patients with chronic autoimmune thyroiditis, with selenomethionine more effective than sodium selenite. But it sets that against a separate review of 9 controlled trials at the same doses for 3-12 months which found selenium did not affect TSH levels, thyroid echogenicity, or health-related quality of life, and whose authors concluded that the evidence does not support the use of selenium supplementation for autoimmune thyroiditis. In pregnancy the picture is mixed and the American Thyroid Association issued a weak recommendation in 2017 against selenium for TPO-antibody-positive pregnant women. The honest summary is that selenium moves a laboratory number without yet being shown to make the patient better - and an antibody titre is not a symptom.

Take 150-300mcg iodine (kelp or potassium iodide) daily WITH 200mcg selenium. Test before high-dosing.

MUST take selenium alongside. Excess iodine can worsen Hashimoto's. Test levels first.

⚠️ What happens if taken in excess:

Excess iodine (>1100mcg/day) can cause both hypothyroidism AND hyperthyroidism. Can trigger or worsen Hashimoto's thyroiditis. Acute iodine ingestion causes burning of mouth and throat, nausea, vomiting, and diarrhea. Very high doses may cause thyroid storm — a medical emergency. MUST be taken with selenium to prevent oxidative thyroid damage.

The iodine interactions are specific and worth knowing by name. ODS states that taking high doses of iodine with antithyroid medications such as methimazole (Tapazole) can have an additive effect and could cause hypothyroidism - directly relevant to anyone treating Graves disease. Two further interactions run through potassium, because potassium iodide is a common supplement form: taken with ACE inhibitors such as benazepril (Lotensin), lisinopril (Prinivil and Zestril) and fosinopril (Monopril), potassium iodide can increase the risk of hyperkalemia, and the same risk applies when it is taken with potassium-sparing diuretics such as spironolactone (Aldactone) and amiloride (Midamor). Those are blood-potassium risks rather than thyroid risks, and they are easy to miss on a page framed entirely around the thyroid. For selenium, ODS names only one drug: cisplatin, which can reduce selenium levels in hair and serum, though whether those reductions are clinically significant is not known, and a Cochrane review found the evidence insufficient to say that selenium reduces cisplatin toxicity. One absence deserves stating plainly rather than being read as reassurance: neither fact sheet names an interaction between selenium and levothyroxine, even though the autoimmune-thyroiditis trials were conducted in levothyroxine-treated patients. That is an unstudied combination being described, not a cleared one, and iodine intake can itself alter thyroid hormone requirements.

1. Iodine - Health Professional Fact Sheet — NIH Office of Dietary Supplements National Institutes of Health (2026)[NIH ↗]
2. Selenium - Health Professional Fact Sheet — NIH Office of Dietary Supplements National Institutes of Health (2026)[NIH ↗]