Iodine: how much is needed and why it is added to salt
Iodine is necessary for the thyroid gland to synthesize hormones, and the daily requirement is measured in micrograms—but it is not always easy to obtain from a standard diet. Therefore, global practice addresses this issue not through dietary advice, but through a carrier: a substance that everyone buys in predictable amounts.
How much iodine is needed
According to EFSA reference values, the adequate intake of iodine for adult men and women is 150 mcg per day. For pregnant and breastfeeding women, it is higher: 200 mcg per day.
This value is based on the relationship between iodine intake and its concentration in urine: 100 mcg/L in urine corresponds to approximately 150 mcg of daily intake in adults. This is why iodine status in populations is assessed via urine analysis rather than blood tests.
Why salt was chosen as the carrier
The WHO has issued a separate guideline on food salt fortification with iodine for the prevention of iodine deficiency disorders. The logic behind choosing the carrier is simple: almost everyone buys salt, its consumption is relatively stable, and fortification is inexpensive and does not alter the taste.
The alternative—encouraging the population to eat more fish and seafood—is less effective: it depends on habits, income, and region.
A side effect of this strategy is that recommendations to eat less salt and the fortification of salt with iodine pull in different directions. The WHO addresses this through monitoring fortification levels rather than abandoning one of the goals. There is a separate article on salt consumption—salt in processed foods.
Where else is iodine found
| Source | What is important to know |
|---|---|
| Marine fish and seafood | the most concentrated sources in a standard diet |
| Seaweed | content varies significantly—from noticeable to very high |
| Dairy products and eggs | contribution depends on feed and farming practices |
| Iodized salt | predictable amount, if the salt is indeed iodized |
| Sea salt without iodization | is not a source of iodine: it is lost during evaporation |
The last row is the most common misconception on the topic: the word "sea" on a salt package has nothing to do with iodine content; only the label regarding iodization matters.
Who needs it most
Pregnancy and breastfeeding are periods when the requirement is higher (200 mcg per EFSA), and the consequences of deficiency affect the child's development. This is a case where the issue should be discussed with a doctor in advance, rather than after receiving test results.
Separately, there are people with thyroid diseases. For them, both deficiency and excess iodine are significant, and the decision regarding supplements is made by the attending physician: self-administering high doses can worsen the condition.
What to do in the kitchen
- Keep iodized salt at home and use it like regular salt—this is the easiest way to address the issue.
- Do not confuse "sea" salt with "iodized" salt. You need to look at the ingredients, not the word on the front of the package.
- Do not increase salt intake for the sake of iodine. Fortification is calculated for standard consumption, not increased intake.
- Do not prescribe iodine supplements to yourself. Doses in them can be dozens of times higher than the daily requirement, and this is a matter for a doctor.
How to read labels and not miss the necessary line—in the article on reading ingredients, and what is generally worth checking on a package in ten seconds—in the article on product composition.
Frequently asked questions
- How much iodine is needed per day?
- According to EFSA reference values—150 mcg per day for adults, 200 mcg for pregnant and breastfeeding women.
- Does sea salt contain iodine?
- No, unless it is specifically iodized: iodine is lost during evaporation. The label regarding iodization in the ingredients matters, not the word "sea" on the package.
- Why is iodine added specifically to salt?
- The WHO recommends the fortification of food salt as a method of mass prevention: almost everyone buys salt, its consumption is stable, and fortification is cheap and does not change the taste of the product.
- How to tell if you are getting enough iodine?
- Iodine status in populations is assessed by concentration in urine, not by blood tests: 100 mcg/L corresponds to approximately 150 mcg of intake per day. Individual assessment and strategy are determined by a doctor.
- Can I take iodine supplements?
- During pregnancy and for thyroid conditions, this is a doctor's decision. Doses in supplements can be tens of times higher than the daily requirement, and both iodine deficiency and excess affect the thyroid gland.
Read next
- Salt in processed food: where it is most abundant and why the salt shaker is not the culprit — The WHO recommendation is less than five grams of salt per day, but the actual intake is about twice that.
- Vitamin D: how much you need, where to get it, and when to get tested — Vitamin D differs from other vitamins in that humans can produce it themselves—in the skin under ultraviolet light.
- Iron and ferritin: what the test shows and why you feel tired — Ferritin is tested more often than any other iron metabolism marker and is most frequently misinterpreted.
This article is for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.
Figures from regulations, guidelines and studies are given as they stood when this article was prepared and may since have changed; check them against the primary sources. This article is not advertising, an offer, or individual advice, and neither the author nor the site owner is responsible for decisions taken on the basis of it.