πΏ Key Takeaways
- Iodine is the primary building block of thyroid hormones β without it, the thyroid can't function.
- Brain development depends on iodine β deficiency is the world's leading preventable cause of intellectual disability.
- Plant-based and reduced-dairy diets carry the highest iodine gap risk.
- Iodized salt, dairy, fish, and seaweed are the main sources β but seaweed can have too much.
- A children's multivitamin with iodine is worth considering for dairy-free or vegan children.
Iodine doesn't get nearly the attention it deserves in parenting conversations β and that's a problem, because iodine deficiency remains the world's leading preventable cause of intellectual disability. In developed countries, most families get enough iodine through iodized table salt and dairy. But as more families shift toward plant-based diets, reduce salt, or avoid dairy, a quiet iodine gap is opening up in children who would otherwise be well-nourished.
Here's what iodine does, who's at risk, and the practical steps every parent should know.
What Is Iodine and Why Do Kids Need It?
Iodine is essential for thyroid hormone production β which regulates growth, metabolism, and brain development in children.
Iodine is an essential trace mineral that the body cannot make. Unlike some nutrients where deficiency takes years to manifest, iodine deficiency can affect thyroid function within weeks β because the thyroid cannot make its hormones without iodine. The thyroid gland essentially concentrates iodine from the bloodstream and uses it as the raw material to build T3 and T4.
Thyroid hormones regulate:
- Metabolic rate β how fast the body burns energy
- Growth β height, bone maturation, organ development
- Brain development β myelination, neuronal migration, synapse formation
- Heart rate and body temperature
- Mood and cognitive function
Iodine and Thyroid Function in Children
π¦ How the Thyroid Uses Iodine
The thyroid gland is a butterfly-shaped gland at the base of the neck. It actively traps iodine from the blood, combines it with the amino acid tyrosine, and produces thyroxine (T4) and triiodothyronine (T3). T4 is the storage/transport form; T3 is the active form that cells actually use. (This is where selenium comes in β selenium-containing enzymes convert T4 to T3 in tissues.) Without iodine, the whole system breaks down. The thyroid swells in an attempt to trap more iodine from the blood β this swelling is called a goitre.
Children with iodine deficiency may show:
- Slow growth and delayed bone maturation
- Fatigue and low energy
- Poor concentration and learning difficulties
- Cold intolerance
- Constipation (hypothyroidism slows the gut)
- Visible goitre (neck swelling) in more significant deficiency
Iodine and Brain Development: The Critical First 1,000 Days
The connection between iodine and brain development is the most compelling reason to pay attention to this mineral. The WHO and UNICEF consider iodine deficiency the world's most significant preventable cause of brain damage and intellectual disability.
Thyroid hormones are essential for neuronal development β migration of neurons, myelination, and synaptic pruning. In the womb and in early childhood, even mild iodine deficiency (without obvious symptoms) has been associated with lower IQ scores, poorer reading ability, and reduced executive function in studies conducted in developed countries.
A landmark UK study (2013, The Lancet) found that children of mothers who were iodine-deficient during pregnancy scored significantly lower on verbal IQ and reading tests at age 8 β even in a country where overt iodine deficiency is rare. The implication: subclinical iodine insufficiency matters.
Who Is at Risk of Iodine Deficiency?
In countries with iodised salt programs, iodine deficiency is largely prevented. But several trends are eroding this protection:
- Sea salt, Himalayan salt, and specialty salts are not iodized β families who use these exclusively miss the most common dietary iodine source
- Dairy-free diets β dairy has historically been a major iodine source in many countries (via iodophor sanitizers used in dairy processing). Oat milk, almond milk, and other plant milks are not naturally iodine-rich and are usually not fortified with iodine.
- Vegan and vegetarian diets that limit fish and seafood
- Low processed food intake β paradoxically, processed foods (made with iodized salt) contribute iodine; whole-food diets with non-iodized specialty salt may not
- Inland areas away from coastal food access
Best Food Sources of Iodine for Kids
Dairy, fish, iodized salt, and eggs are the most reliable iodine sources for children β seaweed varies too much to use as a daily source.
| Food | Serving Size | Iodine (approx.) | Notes |
|---|---|---|---|
| Cod (cooked) | 85g | ~99mcg | Excellent source β mild flavour for kids |
| Whole milk | 240ml (1 cup) | ~56mcg | Traditional primary iodine source |
| Plain yogurt | 170g | ~75mcg | Good dairy iodine source |
| Iodized table salt | ΒΌ tsp | ~95mcg | The most reliable route β but check it's iodized |
| Egg (large) | 1 egg | ~24mcg | Good supplementary source |
| Canned tuna | 85g | ~17mcg | Good source β versatile |
| Shrimp (cooked) | 85g | ~35mcg | Kids often like shrimp |
The Seaweed Caution: More Is Not Always Better
Seaweed (nori, kelp, dulse, wakame) is an extremely concentrated iodine source β but the concentration varies so dramatically by type and origin that it's impossible to dose reliably:
- Nori (in sushi rolls): ~16β43mcg per sheet β reasonable amounts
- Kombu/kelp: 500β3,000mcg per serving β potentially far above the safe upper limit
For children, kelp supplements or large amounts of kelp broth are not appropriate β the iodine content can exceed the Tolerable Upper Level and actually suppress thyroid function (the Wolff-Chaikoff effect). Nori used in sushi occasionally is fine; kelp as a daily supplement is not.
Age-by-Age Iodine Requirements
| Age | RDA (mcg/day) | Tolerable Upper Level |
|---|---|---|
| 1β3 years | 90mcg | 200mcg |
| 4β8 years | 90mcg | 300mcg |
| 9β13 years | 120mcg | 600mcg |
| 14β18 years | 150mcg | 900mcg |
Iodine Supplements for Kids
Switching to iodized table salt and including dairy or fish covers most children's iodine needs β dairy-free children benefit most from a multivitamin with iodine.
For most children eating dairy, fish, and iodized salt, a dedicated iodine supplement is unnecessary. For dairy-free and vegan children, or families using non-iodized salts exclusively, iodine is worth supplementing β most easily through a children's multivitamin that includes iodine.
πΏ Iodine in Children's Multivitamins
The GOJOY Kids Multi With Iron includes 80mcg of iodine per serving β providing 89% of the daily requirement for children ages 4β8 (RDA: 90mcg). For dairy-free or plant-based children who aren't getting iodine from fish or iodized salt consistently, this is a meaningful contribution. As always, discuss with your pediatrician whether a multivitamin is appropriate for your child's specific situation.
Simple fix for most families: Switch from sea salt or Himalayan salt to iodized table salt for everyday cooking. One teaspoon of iodized salt provides ~400mcg of iodine β more than any child needs, but because salt is distributed across meals, average daily intake from light iodized salt use is appropriate.
Frequently Asked Questions
Does sea salt or Himalayan salt contain iodine? οΌ
Is oat milk a good source of iodine for kids? οΌ
Can too much iodine be harmful to kids? οΌ
What are the signs of iodine deficiency in children? οΌ
The Bottom Line
Iodine is the mineral that makes thyroid hormones β and thyroid hormones are what make a child's brain develop, their growth happen, and their metabolism run. For most children eating dairy and iodized salt, deficiency is not a concern. For plant-based or dairy-free children, or families who've switched to non-iodized specialty salts, it's worth addressing β either by returning to iodized table salt or adding a children's multivitamin with iodine. Don't rely on seaweed as a consistent source β the variability is too extreme. The fix is usually simple once you know the gap exists.
