Several everyday foods deliver meaningful amounts of iodine and selenium, and some of the best sources overlap. Seafood, dairy, eggs, and certain nuts top both lists. Adults need about 150 mcg of iodine and 55 mcg of selenium per day, with higher targets during pregnancy (220 mcg iodine, 60 mcg selenium) and breastfeeding (290 mcg iodine, 70 mcg selenium). Here’s where to find both minerals in real meals.
Top Food Sources of Iodine
Seaweed is the most concentrated natural source of iodine, but the range across varieties is enormous. Kombu averages about 2,524 mg per kilogram of dried seaweed, wakame about 140 mg/kg, and nori roughly 37 mg/kg. In practical terms, just two tablespoons of dried nori flakes provide around 116 mcg of iodine, nearly a full day’s worth. Kombu can easily push you past safe limits with a single serving, so it’s best used sparingly, as a flavoring rather than a side dish.
Dairy is a surprisingly reliable iodine source. One cup of low-fat milk provides about 88 mcg, and whole milk is similar at around 82 mcg. A three-quarter cup serving of plain Greek yogurt delivers roughly 87 mcg. The iodine in milk comes partly from iodine-containing sanitizers used on dairy equipment and partly from supplemented cattle feed, which means levels aren’t perfectly consistent. Conventional milk tends to contain significantly more iodine than organic milk, with the gap widest in summer months.
Fish and shellfish round out the iodine picture. Four ounces of raw haddock contains about 250 mcg, well above the daily target. Three ounces of cooked oysters provide around 93 mcg. Cod, pollock, and shrimp are also strong contributors, though exact values depend on species and origin.
One less obvious source: white bread made with iodate dough conditioner. A single hamburger bun can contain as much as 530 mcg of iodine, and two slices of enriched white bread around 296 mcg. Not all commercial bread uses iodate conditioners, so this varies by brand and isn’t listed on most nutrition labels.
Top Food Sources of Selenium
Brazil nuts are in a category of their own. Just one ounce (six to eight nuts) packs about 544 mcg of selenium, nearly ten times the daily recommendation. A single nut delivers roughly 25 to 50 mcg depending on where it was grown. One study found that eating two Brazil nuts per day provided an average of 53 mcg of selenium, though the actual content ranged from 20 to 84 mcg per daily dose. This variability matters: eating a small handful every day could push you well into excess territory, so one to three nuts daily is a reasonable ceiling for most people.
Seafood is the next tier. Three ounces of cooked yellowfin tuna provides 92 mcg, sardines about 45 mcg, and shrimp around 42 mcg. These are cooked, ready-to-eat portions, making them easy to track.
Meat and poultry offer moderate but consistent amounts. A 3-ounce pork chop or beef steak delivers about 37 mcg each. Turkey provides 26 mcg per 3-ounce serving, and ham about 24 mcg. Beef liver comes in at 28 mcg. Even a cup of cooked spaghetti contributes 33 mcg, since wheat absorbs selenium from soil during growth.
Foods That Provide Both Minerals
If you want to cover both bases with fewer foods, focus on seafood, eggs, and dairy. Marine fish ranks highest for combined iodine and selenium content. A serving of haddock or tuna, for example, delivers a meaningful dose of each mineral in a single meal. Eggs contain moderate amounts of both: research places them at roughly 38 mcg of iodine and 24 mcg of selenium per 100 grams (about two large eggs). Milk and yogurt contribute usable iodine with smaller but real amounts of selenium.
The practical takeaway: a diet that regularly includes fish twice a week, dairy or eggs most days, and an occasional Brazil nut or two will comfortably meet both targets without supplements for most adults.
Why These Two Minerals Matter Together
Iodine and selenium aren’t just coincidentally grouped. They work as partners in your thyroid. Your thyroid gland uses iodine as a raw ingredient to build thyroid hormones, but the process of attaching iodine to those hormones generates hydrogen peroxide, a reactive molecule that can damage thyroid cells over time. Selenium-dependent proteins neutralize that hydrogen peroxide, protecting the gland from its own chemistry. Selenium also powers the enzymes that convert inactive thyroid hormone into its active form, the version your cells actually use.
This means a deficiency in either mineral can impair thyroid function, but a deficiency in both is worse than either alone. Animal research has shown that low selenium combined with low iodine produces more severe disruption to thyroid hormone levels than either deficiency in isolation.
Why Levels Vary So Much
The selenium content of plant foods depends almost entirely on soil. Wheat grown in selenium-rich soil (common in parts of the U.S. Great Plains) will contain far more selenium than wheat grown in selenium-poor regions of China, Russia, or parts of Europe. People living in low-selenium areas who eat primarily plant-based diets are at the highest risk of deficiency. In the U.S., this is rarely a concern because grains are sourced from diverse regions, averaging out the variation.
Iodine in food is similarly unpredictable. Dairy iodine fluctuates by season: winter milk contains significantly more iodine than summer milk, likely because cows eat more iodine-supplemented feed during months when they’re not grazing. Organic milk consistently tests lower in iodine than conventional milk, with one large analysis finding a difference of about 6 mcg per 100 grams. Seaweed iodine varies by species, harvest location, and processing method, sometimes by a factor of 100 or more within the same type.
Overdoing It: Upper Limits to Know
The tolerable upper limit for selenium is 400 mcg per day for adults. Beyond that, chronic excess can cause a condition called selenosis, with symptoms including brittle nails, hair loss, garlic-like breath odor, fatigue, and nausea. A single ounce of Brazil nuts exceeds this limit on its own, which is why nutrition guidelines consistently recommend keeping intake to just a few nuts daily rather than snacking freely.
For iodine, the upper limit is 1,100 mcg per day. Excess iodine can paradoxically suppress thyroid function or, in some cases, trigger overactivity. The most common culprits for iodine overload are kelp supplements and kombu seaweed, both of which can deliver thousands of micrograms in a small serving. Nori and wakame are far safer choices if you enjoy seaweed regularly.