Before we delve into the top foods with iodine that help support thyroid function, let’s first take a closer look at what iodine is exactly, how it benefits your health, and how much of it you need daily.
- Jennifer Maeng, MS, RD, CDN, CNSC, clinical dietitian and founder of Chelsea Nutrition
- Nisha Jayani, MD, Nisha Jayani, MD, is a board-certified endocrinologist. She graduated from the Medical University of Lublin and completed her Internal Medicine residency at Westchester Medical Center at New York Medical College.
What is iodine?
“Iodine is a trace element that is found in some foods and added to others. It is also available as a dietary supplement,” says Nisha Jayani, MD, a board-certified endocrinologist with Paloma Health. Iodine doesn’t occur naturally in the body, which means it's essential that we get it through dietary sources.
“Iodine is necessary for the thyroid gland to produce the thyroid hormones T4 and T3,” Dr. Jayani says. “The pituitary gland in the brain releases thyroid-stimulating hormone (TSH) when it detects that thyroid hormones T4 and T3 are low. Cells in the thyroid gland produce T4 and T3 by combining iodine and tyrosine, an amino acid. Once T4 and T3 are created, these hormones are distributed throughout the body to regulate metabolism," as well as support other vital functions as noted above.
Again, iodine is a key player when it comes to all things thyroid health—Dr. Jayani explains that cells in the thyroid gland are the only cells throughout the entire body that absorb this nutrient. “Without iodine, the thyroid gland cannot produce T4 and T3,” she reiterates—and a lack of these hormones can ultimately lead to hypothyroidism (also referred to as an underactive thyroid). While symptoms of hypothyroidism can vary from one person to the next, the most common ones include fatigue, lethargy, constipation, feelings of coldness, and dry skin.
How much iodine do you need?
“The recommended dietary allowance (RDA) for iodine is about 150 mcg for adult men and women, and about 100 mcg more for pregnant and lactating women,” shares Jennifer Maeng, MS, RD, LD, CDN, CNSC, a registered dietitian and founder of Chelsea Nutrition.
To inch your way closer to this RDA to support thyroid functioning—and thus your mood, energy levels, metabolism, and more—consider stocking up on Maeng’s approved list of iodine-rich foods below. Also, keep in mind that, according to the National Institutes for Health, the tolerable upper intake level (UL) for iodine is 1,100 mcg for all adults.
The best foods with iodine, according to a dietitian's recommendations
While seaweed is an excellent source of iodine, Maeng notes that the exact amount of this all-important mineral varies by the type or special of seaweed you're cooking with. Kombu kelp, which she says “is most commonly used to make Japanese soups,” packs the highest amount of iodine at nearly 3,000 mcg per gram. Keep in mind that this is far above the RDA for iodine.
“Cod contains between 65 to 100 mcg of iodine per three ounces,” Maeng says. While she explains that the iodine content of cod varies based on a range of factors—including the region in which it was caught, whether the fish was wild-caught or farm-raised, and its fat content—cod is still a great option to load up on this essential mineral (as are other types of lean fish and seafood).
You’re in luck if you start your morning with probiotic-rich yogurt (or always work on your night cheese à la Liz Lemon), as Maeng mentions that dairy is the largest source of iodine in the standard American diet. With that said, total iodine content in dairy varies across different food sources and their respective fat content. “Per cup, milk can contain between 60 and 115 percent of the RDA for iodine, while plain yogurt contains about 50 percent,” Maeng says. From there, she says that iodine content in cheese varies most significantly, though cottage cheese packs the most at 65 mcg per cup.
4. Iodized salt
According to the Centers for Disease Control (CDC), most Americans have too much sodium in their diets, clocking in at an average of 3,400 mcg while we should really max out at 2,300 mcg. While the majority of this intake typically comes from processed and prepared foods, if you’re going to add salt to your meals, aim to prioritize iodized salt when possible. “A quarter teaspoon of iodized salt contains approximately 70 mcg of iodine,” Maeng says, which clocks in just shy of half your RDA of this micronutrient. Since excess salt and sodium is linked to several harmful health conditions, she advises using a light hand when spinkling your food and not going overboard for the sole purpose of boosting your iodine intake.
“Shrimp is a good source of iodine because, like other fish, they can absorb iodine that is naturally found in seawater,” Maeng says. A three-ounce serving of shrimp will contain around 35 mcg of iodine, plus other essential nutrients like selenium, phosphorus, and vitamin B12, she adds.
Whether you prefer your eggs scrambled, hard-boiled, poached, or prepared otherwise, you’ll be pleased to know that they’re a decent source of iodine with around 25 mcg each. However, egg white omelets won’t pack the same punch, as “a majority of this iodine is from the yolk,” Maeng says.
While prunes are known to be an excellent source of fiber, Maeng also says that they’re a good vegan source of iodine. (In other words, these dried fruits come in handy especially for plant-based eaters, as well as people who are backed up.) “Five prunes contain about 15 mcg of iodine, and they also contain a lot of iron, vitamin K, vitamin A, and potassium,” Maeng says.
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