Iodine Supplements Before, During, and After Pregnancy

Image Credit: Wikimedia Commons. This image has been modified.

Make Sure Iodine Is in Your Prenatal

Although severe iodine deficiency was eliminated in the United States nearly a century ago after the introduction of iodized salt, iodine intake has declined in recent decades. “Public health efforts to limit salt intake to decrease cardiovascular risk, in conjunction with increasing use of kosher salt and sea salt (neither of which contain iodine),” may in part be to blame. Not adding salt to foods is a good thing, as sodium is considered the second leading dietary killer in the world (second only to not eating enough fruit), but if you do add table salt, make sure it’s iodized. “It is a myth (often also false advertising) that ‘natural’ sea salt contains significant amounts of iodine.”

Fruits and vegetables provide iodine, but the amounts can vary depending on where it’s grown and how much iodine is in the soil. Because iodine is particularly important for fetal brain development, there’s a recommendation that “all US women who are pregnant, lactating, or even planning a pregnancy should ingest dietary supplements containing 150 mcg of potassium iodide per day,” which I discuss in my video Iodine Supplements Before, During, and After Pregnancy.

Is there evidence they’re not getting enough? We’d like to see urine levels over 150 mcg/L in pregnant women, but in the United States, pregnant women only average about 125 mcg/L. For example, a recent survey in New York City showed only about half of pregnant women were making the cut.

Don’t most pregnant women take prenatal vitamins, though? Only about half of prenatal multivitamins contain any iodine at all, and so only about one in five pregnant women in the United States are following the recommendations of the American Thyroid Association to take a daily iodine supplement, specifically in the form of potassium iodide rather than seaweed, as the levels in seaweed are subject to natural variability. Though the iodine content was as much as 90 percent off in some of the potassium iodide prenatal supplements, the kelp supplements varied even wider, off by as much as 170 percent.

Now, the American Thyroid Association admits it doesn’t have evidence that the current borderline insufficiency levels are leading to undesirable outcomes and so its rationale that all pregnant women take iodine supplements is a bit tenuous. Until such data are available, though, it figures better safe than sorry.

A randomized, placebo-controlled, interventional trial would answer the question once and for all, but the existing evidence for iodine supplementation during pregnancy is so convincing that it would be considered unethical to randomize pregnant women to a placebo.

When it comes to sufficient iodine intake during pregnancy, I’d recommend: Just do it.

Women eating plant-based diets may find this video of special importance: Pregnant Vegans at Risk for Iodine Deficiency.

This isn’t to say sea vegetables aren’t good for you in their own right. See Which Seaweed Is Most Protective Against Breast Cancer?.

For more videos on having a healthy pregnancy, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

48 responses to “Make Sure Iodine Is in Your Prenatal

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  1. Why do you rec. such a woefully small dose of iodine(only the very minimum)when much research has rec. a much larger one?

    1. The US National Institutes of Health recommend that pregnant women (aged 18+) need 220 mcg per day and lactating women 290 mcg per day. They therefore endorse the the US Thyroid Association’s recommendation to take a 150 mcg supplement daily. However, theyn also note

      ‘Results from a 2010 study however, raise some questions as to the safety of widespread iodine supplementation in areas of relative iodine sufficiency. In this cross-sectional study, pregnant women living in Spain had a significantly increased risk of hyperthyrotropinemia (TSH >3 microU/mL) if they consumed iodine supplements in doses ≥200 mcg/day compared with those who consumed doses <100 mcg/day [49]. These findings suggest that taking higher doses of supplemental iodine during pregnancy could induce thyroid dysfunction in some women and underscore the need for additional research into the effects on maternal thyroid function of iodine supplementation during pregnancy.'

      The 150mcg supplementation recommendation therefore seems a good balance between efficacy and safety.

  2. Seaweed appears to contain iodine — as well as other minerals and vitamins.

    I’ve read suggestions to add Kombu to beans while cooking them, though I’ve never read a reason why. Maybe I’ll start doing it more often.

    I also LOVE dried kelp; I started eating it to replace potato chips (my downfall), and now I eat small amounts 6 times a week. I wonder how much iodine it contains? Since I do use kosher salt (rarely) or sea salt (when baking bread, though again, a reader told me that she never uses it and her bread turns out fine).

    1. I think the kombu is supposed to help the beans cook more thoroughly and/or help prevent flatulence. I do it when I remember to, though I cannot say I’ve noticed a difference.

    2. Seaweed is surely the best source of iodine. Kelp is amazing but I also suggest, dulce, nori, wakame and especially Irish Moss.

      Irish moss is pound for pound the absolute best of foods. I can’t think of a contender.

      1. Ivar Ketilsson,

        You are absolutely correct!! Thank you for the correction.

        I keep getting kelp and dulse mixed up: I eat dulse, from the coast of Maine, NOT kelp.

        Luckily, I always check an old package before I put the item on my grocery shopping list.

        (I don’t know what Irish moss is; I don’t think I’ve seen it in the stores here in CT, USA)

      2. The problem is that the iodine content of seaweed is highly variable. Relying on seaweed might result in getting enough, too much or too little.

        1. Dr. J,

          I’m lucky to live in Iceland so I get wild dulse, kelp, and Irish Moss locally. I recommend trying some Irish Moss, I’m sure you can get it online in your area and a few bags worth will last you a long time.

          I soak mine for a few hours, blend it up into a gel and then I’ll add 1-2 tsp into all my soups, stews, sauces and smoothies.

          You’d need to eat a godly amount of it to get too much iodine. Just keep it steady and the Irish Moss will not only provide iodine but a nutrition profile, unlike any other food.

  3. How often do eat seaweed – for those of you getting iodine through seaweed?

    How often do those of you who are supplementing iodine with pills take iodine pills?

    How often do those of you who use iodized salt use that?

    I know that I am trying to improve my thyroid function and I have not been good at supplementing and iodine is in the D, which I haven’t been taking this Summer and, no, that doesn’t mean that I am getting sun every day. I do get a few minutes of it sometimes.

    1. Deb,
      I take the recommended 150 mcg per day, currently as part of Dr. Fuhrman’s multi but in the past as potassium iodide.

      1. That is the recommended supplement for pregnant women. Unless you are pregnant or lactating, 150 mcg is the total requirement from all sources.

        1. Right, I meant “recommended” as in “recommended daily allowance (RDA)”, which does indeed refer to daily intake from all sources.

          Since I do not eat seaweed or typically ingest much iodized salt, I follow Dr. Greger’s supplement recommendation of a 150 mcg/d supplement and am confident I stay far below the 1100 mcg/d Tolerable Upper Limit.


          – For those who don’t eat seaweed or use iodized salt, a 150 mcg daily supplement – The sea vegetable hijiki (hiziki) should *not* be eaten due to high arsenic levels – Kelp should be avoided as it tends to have too much iodine”

        2. By the way, FF, where did you get the 150 mcg total requirement for pregnant or lactating women from? According to Table 1 of

          the current RDAs in the US are 220 mcg for pregnancy, 290 mcg for lactation. Cf. table below (hope it displays properly).

          The recommendations cited are from: “Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zincexternal link disclaimer. Washington, DC: National Academy Press, 2001.”

          Same recommendations found at

          And WHO recommends 250 mcg/d for pregnancy and lactation.

    2. I just asked my doctor again Deb I I should be taking iodine. He said ‘it doesn’t matter, you can if you want, but it won’t make a difference” . You won’t know if you have an issue with thyroid until you are tested. Maybe you are fine!

    3. I mix 1-2 tablespoons of Irish Moss gel into all my soups, stews, sauces and smoothies. It adds great texture and is incredibly nutritious.

      During the day, I’ll snack on some dulse or kelp. Nori, I eat with sushi or sprinkle it over my salats and bladderwrack I’ll add to my smoothies.

      Basically, I’m adding some type of seaweed to all my meals but never going overboard. Just a sprinkle.

  4. my take would be–how about ceasing to look to inconsistent and frequently inadequately dosed foods for micro-nutrients and instead use supplements in pill, powder or gel form for micro nutrients, and calculate food intake for optimal macro nutrient intake? another Q–were is Dr. Gregor on anti-aging research, intermittent fasting, time restricted eating, latest research on optimal diet.? we seem to be getting every day what 5 people are interested in instead of dealing with present basic issues.

    1. EG,

      I love watercress in salads that we eat out.

      But I don’t think I’ve seen it in stores around here.

      Maybe I should plant some. If my back ever goes back to normal. Right now, my garden beds are full of weeds. It’s very depressing.

  5. Iodine is a major missing mineral, especially in areas of the US where the glaciers passed though (Ohio, western PA, Michigan and parts of Wisconsin) . We test for iodine in our clinic and find many hypothyroid cases are terribly deficient. Our first step in correcting this health condition is using Iodoral (I2 (that’s the mineral iodine) and potassium iodide) with mostly great results. We even treated breast cancer and had mostly amazing results.
    Clinical test for iodine is to give the patient 50mg Iodoral,, throw away the first urine and collect the rest for 24 hours. Urine is then tested for Iodine content. If there is 90% to 95% found then the patient has a good level of Iodine. Otherwise, we treat them with Iodoral.
    For a well written treaties on Iodine, read Dr. David Brownstein’s book, “Iodine, Why You Need It”.

    1. I was just reading about iodine and the breast cancer.

      What interested me was that they mentioned Finland using it, along with putting selenium in their soil while also lowering saturated fats and it helped to reverse heart disease and mortality better than when regions just lowered saturated fat.

      That interests me because they lowered mortality from heart disease, but even after that, they are still number one in Alzheimer’s.

      I ended up looking it up and some researchers think it is mold / environmental toxicity.

      I have brain problems and know that there was mold in our house. I have renovated those areas and the mold is gone, but even after fixing the landscaping and the gutters and digging a drywell and putting in French drains, I still have a basement leak. I can’t afford to dig down for the foundation yet, but boy, I have worked so hard on this house and I am almost finished and it will be the foundation which has to wait for a few years.

      I learned that you can fog it with Concrobium and that Home Depot rents their fogger for $25.

      That is what I am doing right now, but I am wondering how much of my brain problem was mold and how much was aluminum and how much was blood sugar and how much was lack of iodine, etc.

      They talked about clinically using iodine to bring down people’s insulin level and they said that out of 12 people, they got 6 off of insulin altogether just using iodine.

      You have made me more interested.

      1. I have had this sense that most Alzheimer’s is related to diet and I will call it the blocked artery, low blood circulation type. Maybe followed by the insulin resistance, diabetic type. Followed by the Homocysteine type from not eating vegetables and not supplementing B12, etc.

        But Finland fixed a lot of those things and is still number 1.

        That is something to think about.

        1. Okay, are there any researchers out there?

          I would like to hear that they had even higher rates before they lowered their saturated fats and put selenium in the soil and had people take iodine.

          I read that the selenium not being in the soil was a risk factor, so I have added that to my mental list and I do take some Brazil nuts during the month. I don’t take even one per day, but I do take some.

          1. The fact that they improved their diet by decreasing saturated fats, enough to reduce mortality. That should have helped causal factors related to both blood flow and Diabetes.

            They also improved their selenium and iodine.

            All of that wasn’t enough to get them out of the top spot of Alzheimer’s.

            I have been to Finland and I am going to put Vitamin D on the list, but still that is a great big mystery.

            I have to look up what mold actually does to the brain. I do have Dr. Amen’s images in my mind because he talked about having a patient and asking them if they were on drugs and the person said that they weren’t and he said that their brain looked as bad as a chronic drug user.

            1. Okay, Finland makes it in my mind that any Alzheimer’s study trying to see if diet reverses it needs to test for toxins.

              To risk having the dietary methods fail because of an underlying toxin would confuse the science.

              Dr. Ornish, I toss this out on the internet. If people aren’t improving, please, can you test for toxins?

            2. There may be a lag effect.

              Alzheimer’s may take m-a-n-y decades to develop and lower levels of Alzheimer’s may therefore not show uo until say 50 years after major dietary shifts. Cardiovasculat disease usually shows up earlier then Alzheimer’s so you might expect lower heart disease rates to appear before we see lower Alzheimer’s death rates. Just a possibility.

              1. Tom,

                That is something to think about.

                I would think that it would be opposite because it does take so long to develop Alzheimer’s.

                It would seem like if you changed the risk factors for the biggest type of Alzheimer’s, that it would prevent it from progressing.

                What I can say is that reversing heart disease is probably more straightforward.

                (Though the video of Dr Greger explaining why 40 year old vegans die of heart attacks and that study says that people can correct thing after thing and still go wrong.)

                I will use myself as an example because correcting things like giving up junk food and soda didn’t do as much for my brain and did nothing for my waistline, but the Homocysteine issue is easy to blow even after people correct for everything else.

                Did they go off of most of their animal products but not supplement B12? Easy to do. It is easy to correct a whole lot of things and still not have done enough.

                1. The changes in Finland were not as drastic as switching to an Esselstyn or Ornish diet. They were much less dramatic. The Esselstyn diet might reverse the problem but minor changes might only reduce the rate (total number of people affected) or even just slow down progression. Or perhaps it requires much more stringent changes to reduce Alzheimer’s rates than it does to reduce CVD rates. There are many possibble explanations.

                  People start getting heart attacks in their 40s but Alzheimer’s doesn’t really start appaearing until people’s 60s.

                  1. Yes, either it requires more drastic changes, like Esselstyn, or it requires something else on top of the changes. Nuts. DHA. B12 Enough Folate in the diet. Vitamin D3 Selenium etc.

                    The fact that women get it more often and women’s brains switch to running of ketones, which I think they said can be synthesized by using the white matter in the brain, I think is what they said. Maybe they need the fatty acids from beans and fiber and resistant starch or maybe they have fish with mercury or are a lot of cheese with aluminum or it is just plain mold.

                    But most of that is the extra stuff.

                    Somehow changing their saturated fat enough to improve mortality wasn’t enough to knock them out of first place. First place.

                    Think about America and all the excesses and obesity and heart disease and somehow we aren’t in 1st place.

    2. I grew up in Wisconsin and remember the schools used to give us daily goiter pills. They tasted a lot like chocolate, so I was okay with that. :-)

      I wonder if they still give the kids those pills.

          1. YR,
            I grew up in Michigan and remember apples being distributed to us occasionally in elementary school but never supplements!! Goiter pills??
            I find that shocking.

  6. According to Dr. David Brownstein, the number one myth about iodine is that we get enough iodine in salt. Research shows that just 10% of iodine in salt is bio-available—that is, completely absorbed by your body*. Thus, iodized salt provides somewhere between 30-77 μg a day, which is markedly below the recommended amount.

    * Pittman, James I, et al. “Changing Normal Values for Thyroidal Radioiodine Uptake — NEJM.” New England Journal of Medicine,

    1. Thanks, Wallace.

      That is interesting.

      I think I thought it was in my multivitamin (which I don’t take anymore).

      The concept that it wasn’t there in the first place is surprising to me.

  7. It would be good to hear iodine levels and testing methods advice from Dr Greger for non-pregancy everyday health. There seems to be so much contradictory info or uncertainty on iodine and thryroid health, leading people to do nothing.

    Also, which seaweeds are the ones Dr Greger said to always avoid?

    1. +1 I’d love to get Dr. Gregers thoughts on exactly that.

      I believe he recommended against blue-green algae such as Spirulina.

  8. What about if I have no thyroid .Had thyroidcancer.Now cured.The doctor said that I can get cancer back eating iodine rich food or supplements.Think I got thyroid cancer by eating an overdose of kelppills given by a so called natural doctor.Who fooled me and a lot of other people in Sweden.Then he started selling furniture he also sold a lot of calcium-magnesium pills.vitaminpills and told people that they were deadly sick and needed these pills..I do not know what more was in those pills.And where the kelp came from..If they were pulluted.All was a scam.But like everything else in Sweden.Nothing happens to these criminals or medical doctors who hurt patients for life-In Sweden any doctor can can call themselves brain and heartspecialist for ex without having any education in that .Its up to the doctor to have the moral to get the education.And any doctor can call themselves plastic surgeon and do plastic surgery and destroy peoples lives without any consequence-And my skin ,hair,teeth got so bad after they took away the thyroid,What can I do about that.Any suggestions?

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