The best sources of iodine are seafood, dairy products, eggs, and iodized salt. Most adults need 150 mcg of iodine per day, and a single serving of cod or a quarter teaspoon of iodized salt can cover a significant portion of that. Because iodine content in plant foods depends heavily on soil conditions, people who avoid animal products need to be especially deliberate about where their iodine comes from.
How Much Iodine You Need
Adults need 150 mcg of iodine daily. During pregnancy, that rises to 220 mcg, and during breastfeeding it jumps to 290 mcg. Children need less, ranging from 90 mcg for toddlers to 120 mcg for kids aged 9 to 13. The upper safe limit for adults is 1,100 mcg per day. Going well beyond that can disrupt thyroid function, causing either overactivity or underactivity depending on the individual.
Iodized Salt
Iodized salt remains one of the simplest and most reliable iodine sources worldwide. In the United States, iodized salt is labeled at a concentration of about 45 mg of iodine per kilogram of salt. In practical terms, a quarter teaspoon (about 1.5 grams) provides roughly 67 mcg, or about 45% of the adult daily requirement. Two small pinches throughout the day gets most people close to their target.
Not all salt is iodized, though. Sea salt, pink Himalayan salt, and kosher salt typically contain little to no added iodine unless the label specifically says otherwise. If you rely on specialty salts for cooking, you may need to get your iodine elsewhere.
Seafood
Fish and shellfish are among the richest natural sources. Cod stands out: a 3-ounce baked serving delivers around 146 mcg, nearly the full daily requirement in one sitting. Oysters are also excellent, providing about 93 mcg per 3-ounce cooked serving.
Other seafood contributes less but still counts. Fresh bluefin tuna offers around 20 mcg per 3-ounce serving, while canned tuna in water drops to about 8 mcg. Raw shrimp provides roughly 18 mcg per 4-ounce portion, though breaded and fried shrimp from a fast-food restaurant delivers only about 8.5 mcg for the same weight. The type of seafood and how it’s prepared make a real difference.
Seaweed: Potent but Variable
Seaweed is by far the most concentrated natural source of iodine, but the range across varieties is enormous. Nori, the thin sheets used in sushi rolls, contains about 18 mcg per gram, making a small 8-gram portion (roughly two sheets) deliver around 144 mcg. That’s a reasonable amount, close to the daily target.
Kelp and kombu are a different story entirely. Kombu averages around 2,267 mcg per gram, meaning an 8-gram piece could contain over 18,000 mcg of iodine, more than 16 times the upper safe limit. Some kelp varieties reach 7,800 mcg per gram. Wakame falls in between at about 172 mcg per gram, with a small serving providing over 1,300 mcg.
If you eat seaweed regularly, stick with nori or limit kelp and kombu to very small quantities used as seasoning rather than as a dish on their own. The iodine content also varies between brands and batches, so consistency is hard to guarantee with the more concentrated varieties.
Dairy and Eggs
In many Western diets, dairy is actually the primary source of iodine. Cows pick up iodine through their feed and from iodine-based sanitizers used on milking equipment, both of which transfer into the milk. A single cup of milk typically provides 50 to 80 mcg of iodine, and yogurt delivers a similar range per serving. Cheese contributes smaller amounts but still adds up over the course of a day.
Eggs are another steady contributor. The iodine is concentrated in the yolk, and one large egg provides roughly 25 to 30 mcg. Two eggs at breakfast plus a glass of milk can cover most of your daily needs without any extra effort.
Plant-Based Sources
This is where things get tricky. Most fruits, vegetables, grains, and legumes contain very little iodine. The amount depends almost entirely on the iodine levels in the soil where they were grown, and soil iodine varies dramatically by region. A potato contains only about 1 mcg per 100 grams. A 400-gram can of kidney beans provides around 12 mcg. Dried prunes offer just 2 mcg per 100 grams. Dried beans, lentils, and peas average about 3 mcg per 100 grams. None of these will move the needle on their own.
For people on vegan or plant-heavy diets, fortified plant milks are the most practical option. Some brands add iodine at about 22.5 mcg per 100 ml, which puts a standard glass roughly in the range of cow’s milk. But fortification isn’t universal. Check the nutrition label, because many almond, oat, and soy milks contain no iodine at all. Even with a fortified plant milk, a fully plant-based diet may still fall short of the 150 mcg target without iodized salt or a supplement.
Iodine Supplements
Iodine supplements come in two main forms: potassium iodide (a synthetic, standardized form) and kelp-based capsules. Potassium iodide supplements offer a consistent dose, usually 150 mcg per tablet, making it easy to match the daily recommendation. Kelp supplements vary more widely because the iodine content of the seaweed itself is unpredictable. Independent testing has found that some kelp supplements contain significantly more or less iodine than their labels claim.
If you eat dairy, seafood, and use iodized salt regularly, you likely don’t need a supplement. They’re most useful for people on restricted diets, particularly vegans, or for those who live in regions where iodine-poor soil limits the mineral in local foods.
What Can Block Iodine Uptake
Certain foods contain compounds called goitrogens that interfere with how your thyroid absorbs and uses iodine. Cruciferous vegetables like broccoli, kale, cabbage, and Brussels sprouts contain substances that break down into thiocyanates in your body. These block iodine transport into the thyroid and reduce the gland’s ability to incorporate iodine into the hormones it produces. Cassava and sweet potatoes contain a different class of goitrogens with similar effects.
For most people eating a varied diet with adequate iodine, this isn’t a practical concern. Cooking these vegetables reduces their goitrogenic activity. The interaction becomes meaningful mainly when someone is already borderline on iodine intake and eating large amounts of raw cruciferous vegetables daily.
Why Iodine Content Varies So Much
Unlike nutrients such as vitamin C, which is fairly predictable from food to food, iodine levels in the same type of food can swing widely. The iodine in crops depends on how much iodine is in the soil where they grew. Coastal regions tend to have more iodine-rich soil than mountainous or inland areas. Animal products vary based on what the animals were fed and whether iodine-containing sanitizers were used in processing. Even processed foods contribute unpredictably, depending on whether iodine-containing ingredients or additives were used in manufacturing.
This variability is the reason iodized salt was introduced in the first place, and it remains the single most dependable way to ensure a baseline intake regardless of where you live or what else you eat.