Iodine is essential for thyroid hormone synthesis (T3, T4), which regulates metabolism, growth, and neurological development. Iodine content in foods varies widely depending on soil, water, and fortification practices. For guidelines and safety, see the NIH ODS professional fact sheet on iodine.
Top 15 — iodine-rich foods
Indicative values (µg/100 g or per serving); high variability depending on origin/species/farming/product. For precise values, use the USDA FoodData Central and Ciqual table.
- Seaweed/kelp (kombu, wakame, nori): extremely rich, extreme variability (a few grams can exceed 100% of the guideline)
- Cod/haddock/pollock: ~80–200 µg/100 g
- Shrimp/prawns: ~30–60 µg/100 g
- Oysters/mussels/clams: ~40–100 µg/100 g
- Eggs: ~20–50 µg/100 g (≈ 10–25 µg/egg)
- Dairy products (milk, yogurt, cheese): ~10–50 µg/100 g (varies by region/fortification)
- Iodized salt: ~15–25 µg/g (varies by country; check label)
- White fish (various species): ~50–120 µg/100 g
- Turkey/chicken: ~10–30 µg/100 g
- Potatoes (with skin): ~30–60 µg/100 g
- Navy beans/lima beans: ~10–30 µg/100 g
- Cranberries: ~30–50 µg/100 g
- Strawberries: ~10–15 µg/100 g
- Fortified bread/cereals: variable (check label)
- Prunes: ~10–15 µg/100 g
Variability is major: alternate fish, seafood, eggs, dairy, and use iodized salt moderately. Seaweed is highly concentrated: a small portion often suffices as an occasional boost.
Optimizing absorption
- Vary sources to smooth out geographical variability in iodine content.
- Moderate cooking: avoid prolonged overcooking; some iodine may be lost in cooking water.
- Iodized salt: a practical and economical source; use in moderation for overall sodium control.
- Goitrogens: certain raw cruciferous vegetables (cabbage, broccoli) contain compounds that can interfere with iodine utilization when consumed in very large amounts; normal dietary intake is not a concern for most people.
- Selenium and thyroid: balance with other trace elements (e.g., selenium) supports thyroid function.
Daily guidelines (recommended intakes)
Usual guidelines: ≈ 150 µg/day for adults (references vary slightly by organization). See the NIH ODS professional synthesis and European reference values.
| Population | Daily guideline |
|---|---|
| Adults | ≈ 150 µg/day |
| Pregnancy | ≈ 220–250 µg/day |
| Breastfeeding | ≈ 250–290 µg/day |
Risks, interactions and precautions
- Excess iodine: thyroid dysfunction (hyperthyroidism or hypothyroidism), goiter; UL typically ≈ 600 µg/day for adults (international references; some differences exist between organizations). See NIH ODS safety section.
- Seaweed variability: iodine content highly fluctuating; moderate frequency of consumption, especially for high-iodine varieties like kombu.
- Thyroid conditions: if you have thyroid disease or take thyroid medications, discuss iodine intake with a healthcare professional.
- Interactions: caution with multi-mineral supplementation (balances with selenium, zinc, copper).
Avoid self-medication with high doses. Prioritize a varied diet; adjust intake with a healthcare professional in case of thyroid disease, pregnancy, or long-term supplementation.
Sources and further reading
- Mechanisms, needs, safety: NIH ODS professional fact sheet – Iodine.
- Composition tables: USDA FoodData Central, Ciqual table (ANSES).
