Iodine is a trace mineral found in food — and it’s one of the most important nutrients your growing baby needs in the womb. Iodine is crucial for the development of baby’s brain, and skeletal and central nervous system.
At the same time, our own grown-up bodies require only the teeny-tiniest amount of it (just 5 grams over the course of a 70-year lifetime!).
Most Americans get enough iodine in their everyday lives, but historically that wasn't always the case. Before the introduction of iodized salt in the 1920s, severe iodine deficiency affected many people in the U.S. and negatively impacted intellectual development in babies and children.
Today, the Centers for Disease Control still advises pregnant women to monitor their intake because iodine deficiency remains a global problem and some mild cases do show up stateside.[1]
The reason? Americans used to eat more home-cooked meals made with iodized table salt, but today’s fast-food-heavy diet contains much less iodine since the salt in processed foods isn’t usually iodized. What’s more, sea salt isn't iodized either — and many people cook with that instead of iodized salt.
So what can you do to be sure you are getting enough of this mineral during your pregnancy? It can be tough to know, since iodine amounts aren’t listed on consumer packaging. Read on to find out more.
Why is iodine important in pregnancy?
Iodine helps maintain the normal function of the thyroid, a gland in the base of your neck. The thyroid regulates the hormones controlling your metabolism, heart rate, body temperature and other core body functions.
Getting enough iodine ensures that your baby develops a healthy and normal thyroid too. In very rare cases where a fetus has an underdeveloped thyroid, it can lead to negative effects later in life, like developmental delays, deafness, impaired growth, cognitive deficiencies, and other problems.
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Iodine is also key in lactation, since you pass iodine on to your baby through your breast milk. That means the iodine you consume during pregnancy continues to support your baby's brain and thyroid development until she stops breastfeeding and fully transitions to solids.
How much iodine does a pregnant woman need?
Because iodine is so critical to fetal health, the National Institutes of Health’s Office of Dietary Supplements recommends women get more of it than usual during pregnancy and even more still when they’re breastfeeding, specifically 150 micrograms (mcg) of iodine per day before pregnancy, 220 mcg during pregnancy, and 290 mcg while breastfeeding.
You may get sufficient iodine from your prenatal vitamin, but it depends on the type of supplement you’re taking. In fact, recent research has shown that only about half of the prenatal vitamins sold in the U.S. contain iodine.
Both the American Thyroid Association[2] and the American Academy of Pediatrics (AAP) recommend that pregnant and breastfeeding women take a daily multivitamin or prenatal supplement containing 150 mcg of iodine.
These are trusted guidelines from reputable sources, but make sure you discuss any supplement you’re thinking of taking with your doctor first. You don’t want to overdo it.
Which foods are high in iodine?
Besides checking whether your prenatal vitamin contains iodine, the best way to ensure you're getting enough is by eating a healthy pregnancy diet. Focus on whole foods that are natural sources, including the following:
- Baked cod (99 mcg in 3 ounces)
- Plain, low-fat yogurt (75 mcg in 1 cup)
- Low-fat milk (56 mcg in 1 cup)
- Fish sticks (54 mcg in 3 oz)
- Enriched bread (45 mcg in two slices)
- Shrimp (35 mcg in 3 oz)
- Enriched macaroni (27 mcg in 1 cup boiled)
- Large egg (24 mcg)
- Canned light tuna (17 mcg in 3 oz)
- Creamed corn (14 mcg in 1/2 cup)
- Cheddar cheese (12 mcg in 1 oz)
- Dried prunes (13 mcg in five)
- Raisin bran cereal (11 mcg in 1 cup)
- Apple juice (7 mcg in 1 cup)
You can get additional iodine by cooking with iodized salt. A 1/4 teaspoon provides 71 mcg, but keep your total sodium intake in check by staying under 2,300 milligrams a day. Eating too much salt can increase swelling and elevate your blood pressure.
Sometimes seaweed can be a good source of iodine, but levels vary widely — from 16 to 2,984 mcg in a 1-ounce serving. As long as you aren't allergic, it's likely okay to include some seaweed occasionally in your diet.
But skip seaweed supplements, since they’re not regulated by the Food & Drug Administration (FDA) before they go to market, and the amount of iodine listed on labels isn't always accurate.
Which foods are low in iodine?
While they can be part of a healthy pregnancy diet, keep in mind that these other foods are low in iodine:
Fruits and veggies
Fresh meats
Egg whites
Rice, couscous, oatmeal, and salt-free varieties of crackers and pasta
Baked goods made without iodized salt
Unsalted nuts and nut butters, jam and honey
Fresh herbs and spices
The AAP also recommends that pregnant and breastfeeding women avoid nitrates, in part because they can impact your body's ability to absorb iodine.
Nitrates are compounds used as preservatives and are found in many foods, including deli meats and processed foods like hot dogs, sausages and bacon. Not all forms of nitrates are bad, but some can be harmful. Look for "nitrate-free" on the label.
Can you overdo iodine?
Yes, you can. The NIH recommends that you consume no more than 1,100 mcg of iodine daily. Exceeding that amount may put you at risk of hypothyroidism and potentially more serious problems.
So while taking a prenatal supplement containing iodine with 150 mcg is okay, most doctors don't recommend taking a separate iodine supplement, since most start at 500 mcg. Talk to your doctor to be sure you’re getting the right amount of iodine during pregnancy and while you’re nursing.
Are you getting the right amount of iodine?
If you're concerned about your iodine levels, talk about it with your doctor or a nutritionist, who can advise on diet and your prenatal vitamin. It’s unlikely that a urine test (the only way to test iodine levels, which are not usually screened by practitioners) will be necessary.
When levels of iodine are low or deficient, symptoms can include an enlarged thyroid (goiter) or nodules on the base of your neck. Hypothyroidism is another concern, especially if you have chills, muscle weakness, fatigue, pale skin, puffiness, joint or muscle pain, or constipation.
Fortunately, iodine is easy to work into meals and snacks. By focusing on whole foods, cooking with iodized salt, and taking your prenatal vitamins as directed, you should easily get all the iodine you and your baby on board need.
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