Compound or practice · Supplement
Iodine
Essential for thyroid hormone — a deficiency to prevent (iodized salt) and an excess that can itself cause thyroid trouble.
- Overall grade
- Grade B
- Last revised
- 2
- graded outcomes
- 0
- references listed
A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.
1 at grade A · 1 at grade B — 2 graded rows
What is known
Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.
- Deficiency disorders / fetal cognitionEvidence grade A
Especially pregnancy
Largehigh
- Thyroid dysfunction (excess)Evidence grade B
Too much also harms
Moderatehigh
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Caution with Levothyroxine: Alters thyroid hormone needs; coordinate with the prescriber.
Interactions
Documented pairings with supplements and medicines. A medicine on this list is a conversation for whoever prescribes it.
LevothyroxineCaution
Alters thyroid hormone needs; coordinate with the prescriber.
The evidence in words
What it is
Iodine is the trace element the thyroid uses to build its hormones. Salt iodization solved widespread deficiency, but it re-emerges in people avoiding iodized salt, dairy, and seafood, and matters intensely in pregnancy for fetal brain development.
How it works
The thyroid concentrates iodine and attaches it to tyrosine residues to make T4 and T3, which set metabolic rate throughout the body. Both too little and too much disrupt hormone production.
What the evidence shows
Grade A for preventing deficiency disorders (goiter, and critically, cretinism/impaired cognition when deficient in pregnancy). But supplementation above needs is not benign — excess iodine can trigger both hypo- and hyperthyroidism, especially in susceptible people. This is an adequacy nutrient, not a booster.
How to use it
Iodized salt, dairy, and seafood cover most people. Pregnancy and lactation raise needs; prenatal vitamins typically include ~150 µg. Avoid high-dose kelp/iodine supplements.
Safety & interactions
High doses can induce thyroid dysfunction; kelp supplements deliver erratic, sometimes excessive amounts. Stay near requirements. levothyroxine — Alters thyroid hormone needs; coordinate with the prescriber.
Bottom line
Use iodized salt or eat seafood/dairy; ensure adequacy in pregnancy. Don't megadose — the thyroid dislikes both extremes.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Adequacy
- Iodized salt / seafood; ~150 µg in pregnancy prenatals.
Related reading
Entries that share this one's tags or conditions.
- Iodine for Deficiency disorders / fetal cognitionEvidence grade A — Especially pregnancyEvidence grade A
- Iodine for Thyroid dysfunction (excess)Evidence grade B — Too much also harmsEvidence grade B
- Iodine: dosage and how to take itIodized salt / seafood; ~150 µg in pregnancy prenatals.Evidence grade B
- Iodine: side effects, safety & interactionsHigh doses can induce thyroid dysfunction; kelp supplements deliver erratic, sometimes excessive amounts. Stay near requEvidence grade B
Sources
This entry lists no references of its own.
Last revised . A grade is this entry's reading of the evidence, not medical advice.