Iodine is found in seafood, dairy products, eggs, seaweed, and iodized salt. These are the richest everyday sources, though the mineral also shows up in some unexpected places outside the kitchen. Your body needs iodine to produce thyroid hormones, which regulate metabolism, growth, and brain development. Most adults need 150 mcg per day, a small amount that’s easy to get from a varied diet but also easy to miss if your eating patterns are limited.
Seafood and Seaweed
Ocean water naturally concentrates iodine, which is why fish and seaweed top the list of dietary sources. A 3-ounce serving of baked cod delivers about 146 mcg of iodine, nearly the entire daily requirement for an adult in a single portion. Other saltwater fish like tuna and shrimp also provide meaningful amounts, though cod is one of the richest.
Seaweed packs even more iodine into a smaller serving. Just two tablespoons of dried nori (the type wrapped around sushi) contains around 116 mcg. Kelp and other brown seaweeds can contain dramatically higher concentrations, sometimes thousands of micrograms in a single serving. This makes seaweed a powerful source but also one worth being careful with. Eating large amounts of kelp regularly can push iodine intake well past safe levels and disrupt thyroid function.
Dairy Products
Milk, cheese, and yogurt are among the top iodine sources in the typical Western diet. This isn’t because cows naturally produce iodine-rich milk. It’s largely because dairy farmers use iodine-based sanitizers on milking equipment and because cattle feed is often supplemented with iodine. The result is that dairy ends up being a surprisingly reliable source.
A three-quarter cup serving of plain nonfat Greek yogurt provides about 87 mcg of iodine, while whole-milk plain yogurt comes in around 55 mcg for the same serving size. Flavored varieties fall in a similar range, roughly 53 to 71 mcg per serving depending on the brand and type. A cup of milk typically provides a comparable amount. For people who eat dairy regularly, these foods often contribute more to daily iodine intake than any other category.
Eggs
One large raw egg contains about 25 mcg of iodine, and a hard-boiled egg provides around 31 mcg. Most of that iodine sits in the yolk, not the white. If you eat two eggs at breakfast, you’re getting roughly a third of your daily iodine needs from that meal alone. The iodine content of eggs varies depending on what the hens were fed, so eggs from iodine-supplemented flocks can be noticeably higher.
Iodized Salt
Iodized table salt is the single most important public health tool for preventing iodine deficiency worldwide. In the United States, salt manufacturers voluntarily add iodine to table salt, and roughly a quarter teaspoon provides a significant portion of the daily requirement. This fortification program, which began in the 1920s, largely eliminated goiter (an enlarged thyroid caused by iodine deficiency) in developed countries.
One important distinction: not all salt is iodized. Sea salt, kosher salt, Himalayan pink salt, and most specialty salts contain little to no added iodine unless the label specifically says otherwise. If you’ve shifted away from regular table salt, you may be getting less iodine than you think. The same goes for processed foods. While they’re often high in sodium, manufacturers typically use non-iodized salt, so packaged snacks and restaurant meals don’t contribute much iodine to your diet.
Why Your Body Needs It
Iodine’s primary job is fueling thyroid hormone production. Your thyroid gland, a butterfly-shaped organ at the base of your throat, absorbs iodine from the bloodstream and uses it to build two key hormones. These hormones control how quickly your cells burn energy, how your body regulates temperature, and how children’s brains and bones develop. Without enough iodine, the thyroid simply cannot manufacture these hormones.
The recommended daily intake is 150 mcg for most adults. During pregnancy, that rises to 220 mcg because the developing baby’s brain depends heavily on thyroid hormones. During breastfeeding, the requirement increases further to 290 mcg, since breast milk is the infant’s sole iodine source.
Non-Food Sources of Iodine
Iodine appears in several medical and industrial products. Antiseptic solutions used to clean wounds before surgery contain iodine as the active disinfecting agent. Contrast dyes injected during CT scans and certain X-rays also contain significant amounts of iodine to help blood vessels and organs show up clearly on imaging. The FDA has flagged that these contrast injections can temporarily affect thyroid hormone levels, particularly in newborns and young children.
Some dietary supplements also contain iodine, either as a standalone mineral or as part of a multivitamin. Kelp-based supplements in particular can deliver highly variable and sometimes excessive doses.
Foods That Interfere With Iodine
Certain vegetables contain natural compounds called goitrogens that can interfere with how your thyroid absorbs and uses iodine. Cruciferous vegetables like broccoli, cabbage, cauliflower, Brussels sprouts, and kale fall into this category. Soy products can have a similar effect. In practice, this only becomes a real concern if you eat very large amounts of these foods while also getting too little iodine. Cooking reduces goitrogen activity significantly, so a normal intake of cooked cruciferous vegetables is not a problem for most people.
How Much Is Too Much
While iodine deficiency gets the most attention, excess iodine can also cause thyroid problems. Paradoxically, both too little and too much iodine can lead to either an overactive or underactive thyroid. For most adults, the safe upper limit is 1,100 mcg per day. Staying below that threshold is easy with normal food intake. The risk of overdoing it comes mainly from concentrated sources: kelp supplements, large daily portions of seaweed, or multiple iodine-containing supplements stacked together. If you’re eating a mix of seafood, dairy, eggs, and using iodized salt, you’re almost certainly in the right range without needing to count micrograms.