Iodine
Deficiency prevention with world-class evidence, and a megadose culture pointed at the gland it can break.
B-
Evidence grade
B
Worth it
$5-10/month
Typical cost
DoseAim for the requirement, not multiples of it: 150 mcg/day for adults, 220 in pregnancy. Do not megadose iodine: intakes above the 1,100 mcg/day upper limit can switch the thyroid off or, in people with nodular goiter, switch it pathologically on, and kelp supplements are notorious for delivering milligrams per serving with wide lot-to-lot variation. A standard multivitamin or iodized salt covers the requirement; anyone correcting a suspected deficiency belongs in a clinician's testing loop (urinary iodine and thyroid function), not a titration-by-feel protocol.
BasisIodine grades like iron: indispensable and proven where deficient, valueless where sufficient, and actively harmful in excess through the very gland it feeds.
Iodine is the raw material of thyroid hormones T4 and T3. We grade Iodine B- on evidence and B for worth-it at about $5-10 per month.
What it does
Iodine is the raw material of thyroid hormones T4 and T3. It is needed in microgram amounts, stored in the thyroid, and supplied by iodized salt, dairy, eggs, and seafood. Online culture sells it in milligram drops as a near-universal remedy; physiology disagrees in both directions, and this record is built around that disagreement.
What the research says
Preventing iodine deficiency protects the developing brain; this is among the most proven facts in nutrition
Evidence: strong. Iodine deficiency is the world's leading preventable cause of intellectual disability. In deficient regions, supplementation in pregnancy and childhood protects IQ at population scale, and iodized salt is one of public health's complete successes. The requirement is small and specific: about 150 mcg/day for adults, 220 in pregnancy, 290 in lactation.
In iodine-replete adults, additional iodine has no demonstrated benefit
Evidence: moderate. For the already sufficient, the thyroid takes what it needs and the surplus is excreted or, past thresholds, disruptive. Claims for supplemental iodine in replete people (energy, 'thyroid support,' detox) have no trial basis. Most US adults are sufficient; mild insufficiency appears in some groups, notably pregnant women and people avoiding dairy, eggs, and iodized salt, which is an argument for attention to intake, not for megadoses.
Iodine grades like iron: indispensable and proven where deficient, valueless where sufficient, and actively harmful in excess through the very gland it feeds. Its B- reflects the strength and consequence of the deficiency evidence, among the strongest in nutrition science, discounted by how small the genuinely deficient share of this library's likely readers is, and by an online megadosing culture this record explicitly warns against.
Is it worth it?
Evidence (B-) clears the leaderboard floor, and the worth-it grade is the derived value at this price: about $7 a month. The grade applies to meeting the requirement, as with iron it does not extend to excess. Derived from the October 2026 worth-it model.
Typical cost
$5-10/month
Common form, not a brand recommendation
Dosage context established
Aim for the requirement, not multiples of it: 150 mcg/day for adults, 220 in pregnancy. Do not megadose iodine: intakes above the 1,100 mcg/day upper limit can switch the thyroid off or, in people with nodular goiter, switch it pathologically on, and kelp supplements are notorious for delivering milligrams per serving with wide lot-to-lot variation. A standard multivitamin or iodized salt covers the requirement; anyone correcting a suspected deficiency belongs in a clinician's testing loop (urinary iodine and thyroid function), not a titration-by-feel protocol.
Worth-it leaderboard
Iodine ranks #15 for worth-it.
That rank comes from the gated model on the leaderboard: evidence grade B- or better, purchasable, and useful beyond a single occasion, then scored on evidence against monthly cost.
- 1AWorth itCreatine evidence A-~$5-10/mo
- 2AWorth itCaffeine evidence B+~$5-10/mo
- 3AWorth itVitamin D evidence B~$5-8/mo
See the full worth-it leaderboard →
When the evidence moves a grade, this ranking moves with it. Thursday is where you hear it first.
Safety notes
Both directions of thyroid dysfunction can be triggered by sudden high iodine loads: hypothyroidism via the Wolff-Chaikoff effect (usually transient, not always) and hyperthyroidism in autonomous nodular goiter (the Jod-Basedow phenomenon). People with Hashimoto's or Graves' disease, and anyone on thyroid medication or amiodarone (itself iodine-rich), should treat iodine supplements as a clinician conversation. New fatigue, palpitations, or weight change after starting kelp or Lugol's drops is a reason to stop and get thyroid function tested.
Longevity Lab Report
Iodine news. Graded when it happens.
The grade on this page stays free. The email carries the news on iodine: expert moves, dose changes, and what is working, in plain English every Thursday.
Changelog
Last updated 2026-10-23
- 2026-10-23|Graded from the deficiency literature and the excess literature together, in the shape of this library's iron record: a nutrient whose value and whose harm both depend entirely on where the reader starts. The dosage guidance carries the caution in-line, per this library's placement rule for hormone-active nutrients.
- 2026-10-23|Not listed under any goal: deficiency prevention in pregnancy is population medicine, not a reader-goal claim, and the replete-adult file is empty.
The week's longevity and biohacking news.
This grade for Iodine rests on the record above. When a new result changes that record, the grade changes with it, and the Thursday email is where the change lands first: the week's longevity and biohacking news, in plain English, linked back to the reasoning on this page.
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Every grade follows a published rubric, and sponsors never change one. When the evidence moves a grade, Thursday is where you hear it first, before you renew a stack that stopped earning its cost.