Iodine RDA Table
| Life stage | RDA (µg/day) |
|---|---|
| Infant 0–6 mo | 110 (AI) |
| Infant 7–12 mo | 130 (AI) |
| 1–8 years | 90 |
| 9–13 years | 120 |
| 14+ years | 150 |
| Pregnancy | 220 |
| Lactation | 290 |
| Food | Portion | µg | %DV |
|---|---|---|---|
| Cod, cooked | 3 oz | 99 | 66% |
| Greek yogurt, plain, nonfat | 8 oz | 116 | 77% |
| Iodized salt | 1/4 tsp | 71 | 47% |
| Enriched white bread | 2 slices | 45 | 30% |
| Shrimp, cooked | 3 oz | 35 | 23% |
| Egg, hard-boiled | 1 large | 24 | 16% |
| Tuna, canned in oil | 3 oz | 17 | 11% |
Iodine's requirement is almost comically small - 150 micrograms a day for adults, less than a quarter teaspoon of iodized salt - and the consequences of missing it are almost comically large: the thyroid needs it to build the hormones that set metabolic rate, brain development in the fetus runs on the mother's supply, and iodine deficiency remains the world's leading preventable cause of intellectual disability.
American iodine is a public-works story: the Great Lakes 'goiter belt', where iodine-poor soil made neck swellings endemic, was fixed in 1924 by iodizing table salt - one of the cheapest mass-health wins ever recorded. But the modern twist is that roughly half the iodized salt never reaches anyone: processed and restaurant foods are made with plain salt, so the iodized carton only counts in a home kitchen.
The warning on this page is aimed at the wellness aisle, not the salt shaker: kelp and seaweed supplements carry wildly variable iodine - a single kelp tablet can deliver several milligrams, several times the 1,100 mcg adult upper limit - flipping the risk from deficiency to hyperthyroid symptoms. The food table gets you to 150 mcg with cod, yogurt and bread; the ocean-green capsule is where iodine becomes uncountable.
How to use
- Find your row: 150 mcg from age 14; 120 at 9-13; 90 from ages 1-8; 110-130 for infants; 220 in pregnancy and 290 while breastfeeding - the largest pregnancy jump of any mineral on this site.
- Cover it at home: a quarter teaspoon of iodized salt (71 mcg) plus two slices of enriched bread (45) plus an egg (24) already clears 140 mcg - add fish or dairy weekly and the margin is comfortable without any supplement.
- Audit the sea-greens: if kelp, bladderwrack or seaweed pills are in the routine, read the iodine line - contents vary by orders of magnitude between batches, and 'a little thyroid support' can outdose the UL by multiples; whole seaweed in food portions is a different, countable story.
Frequently asked questions
How much iodine do I need per day?
The NIH RDA is 150 mcg for everyone from age 14; 120 mcg at ages 9-13; 90 mcg from ages 1-8; infants run 110-130 mcg as an adequate intake. Pregnancy raises the target to 220 mcg and breastfeeding to 290 - the steepest climb on this site, because the fetal thyroid is being built from the mother's circulating supply. The adult upper limit is 1,100 mcg a day.
Does iodized salt really cover my iodine?
A quarter teaspoon of iodized salt delivers about 71 mcg - half the adult RDA - so yes, if the salt is iodized AND you cook with it at home. The catch: most restaurant, snack and packaged food is made with plain salt, which carries essentially none, and fancy salts (kosher, sea, Himalayan) are usually uniodized. Roughly half of American table-salt iodine exposure has quietly migrated out of the shaker since the 1970s - the salt you season with counts, the salt factories use does not.
What foods are highest in iodine?
Cod leads the fish column at about 99 mcg per 3 ounces, Greek yogurt carries 116 per cup, shrimp 35, one egg 24, canned tuna 17. Dairy is a quiet workhorse - milk and yogurt iodine partly reflects fortified feed and iodine-based sanitizing of equipment - and enriched bread adds 45 per two slices. Seaweed is the outlier: kelp can carry hundreds of micrograms per serving with wild batch-to-batch variance, which is food-level iodine done by weight but supplement-level iodine done by roulette.
Why does pregnancy need so much more iodine?
The fetal thyroid begins hormone production around mid-pregnancy, but before and after that the baby runs on maternal thyroid hormone crossing the placenta - and the mother's own production rises about 50% during pregnancy, which is why the RDA jumps from 150 to 220 mcg (290 while breastfeeding, since milk is the infant's only source). Severe maternal deficiency causes cretinism - the classic preventable intellectual disability - and even mild maternal deficiency measurably lowers childhood IQ in cohort studies, which is why prenatal vitamins are checked for their iodine line.
Can you get too much iodine?
Yes, and the modern route is supplements rather than food: the adult UL is 1,100 mcg a day, and kelp-based 'thyroid support' products routinely exceed it several-fold per tablet. Acute overdosing can flip the thyroid into hyperactivity or, paradoxically, shut it down (the Wolff-Chaikoff escape failure), and chronic excess inflames it. Dietary iodine - fish, dairy, eggs, iodized salt in home cooking - sits comfortably below the line; the capsule is where the dose goes uncounted.