Doctor's Note

For more videos on iodine, see:
Pregnant Vegans at Risk for Iodine Deficiency                                                                                                                                                    Can Gargling Prevent The Common Cold?
Which Seaweed is Most Protective Against Breast Cancer?

Also check out my associated blog posts: How much pus is there in milk?The Best DetoxOptimum Nutrition RecommendationsDo Eden Beans Have Too Much Iodine?; and The Best Way to Prevent the Common Cold?

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  • Michael Greger M.D.

    See yesterday’s video about getting enough iodine, and the corresponding blog post How much pus is there in milk? As always, feel free to leave any questions you may have below.

    • I get that Kelp affects the thyroid-but what is hypothyroid? Do you think it is effective to treat it with a measured amount of kelp instead of drugs? (If you get the blood tested to see the effects?).
      And just how much kelp will “hurt” you? If you “od” on it one day (darn I am drinking smoothie with kelp in it now!) then it will leave your system eventually, right?

      • Wegan

        After seeing these videos I stopped using kelp but I apparently did not eat enough other seaweed because my TSH and LDL levels were high on my last blood test. After doing some research I found Lynn Farrow’s book about iodine. Again the medical “wisdom” of the day is wrong. Iodine is needed in greater quantities because of the toxic halogens the environment. Traditionally Japanese people ate much more than the recommended amount of iodine in foods and perhaps that is why their breast cancer rates were so much lower. There is a protocol to supplementing iodine because of halogen detox side effects. has some information.

    • Mykel18

      Hi Dr. Greger, thank you for everything you do an amazing work. I have been wondering, my mother switched to a plant based diet after a breast cancer diagnosis. Few years ago she had her thyroid gland irradiated. She now takes syntroid. Is there an issue about taking iodine supplement with this condition? Thank you very much for you answer .
      Ps: I appreciated a lot your videos on cancer topics, thank you.. ( i have posted this comment already on another topics discussion accidentally)

  • JJ

    OK, so this is the one that mentions kombu. Clearly kombu can be of concern and I’m glad you have posted this video now. I’m low on my kombu and may not be replenishing it.

    I still don’t think my question is answered, however. The video clearly says to stay away from eating kombu a lot. I’m trying to figure out if this would be too much or not: A sheet of 2×4 inches of kombu in a pot of grains. And then that pot of grains or beans gets eaten over the course of a *week*. Is that too much iodine? Not safe?

    Also, does all kombu have too much iodine or are there certain brands which are safer?

    Here’s why it matters to me: Your videos make it clear that it is vital to get enough iodine. I don’t like (and am rarely compliant about) taking pills, so I’d like to get my iodine from my diet. I do like nori, but I’m still not clear on how much nori I have to eat and I’m wondering if I have to eat X sheets of nori every week (day?) or if I can mix it up by putting some kombu in a pot of grains or beans. Would spreading out that little bit of kombu over the course of a week be just right or is that still too much?


    • des

      I’m bothered by the same question. How much is a gram of kelp? I use kombu to cook grains and given it’s divided between a bunch of people and is cooked into the food, I don’t think its an issue.

    • Michael Greger M.D.

      Thank you for the question JJ. My favorite questions are the practical ones! Please see my video Avoiding Iodine Deficiency for specifics on quantities.

      • Leslie

        Are you at peace these days consuming sea vegetables considering the plastic microbeads littering the ocean, as well as red tides, pollution, and chemicals that can’t even be tested for?

  • VeganRyan

    Dr. Greger –

    I’m a big fan of tuno salad sandwiches (basically mashed garbanzos in place of tuna). I add some kelp granules to give it that “seafood” flavor.

    I use about 1/4 tsp of the granules per sandwich, which according to the label is only about 50%DV of iodine.

    Is this much kelp still too much?

    • JJ

      VeganRyan: Any chance of posting your tuno recipe? Or pointing me to the book that has it? (Sounds good to me!)

      I wonder if ground up nori in place of kelp would give it the same flavor? My city has a vegan restaurant which serves “phish and chips”. Put aside for a second the unhealthy nature of fried food – what they do is pretty cool: the fish part is tofu slabs. The batter part includes ground up (I think) nori. This ground up sea food (of some kind – now that I think about it, I should ask which kind) really gives it a perfect fishy flavor. I liked the taste and the idea lot. Your tuno idea really intrigues me. Thanks if you get a chance to share the recipe!

      • VeganRyan

        I basically combine the recipes from Colleen Patrick-Goudreau’s “The Vegan Table” and the Happy Herbivore website ( I use my favorite ingredients from each recipe, and omit a few.

        The mashed garbanzos are an awesome visual and texture replacement for fish, and of course are much healthier. Enjoy. :-)

        • JJ


    • Michael Greger M.D.

      If that’s just 50% of the DV, then it would just be 75 mcg. Sounds like a great way to get your iodine. Can’t wait to try your recipe! Nice to have a sandwich and not worry how much brain damage the mercury is causing:

  • Hi from New Zealand – I’ve just signed up. Thank you for all the work you put into providing these excellent little videos! – I look forward to watching more. I read the comments and have similar questions – I clicked ‘Supplementary Information’ hoping it would lead to detailed info as a follow up/background to the video. Is that generally provided? Or links to study the issues further? I am on PLant-based Wholefoods, and get my blodds donw regularly to monitor zinc, Vit D (I’m low), B12, iron,etc (I’m high). My GP,(MD), tested me for iodine and I was low. She recommended supplementing. I prefer to take seaweed instead of the drops. The test is convoluted so it would be difficult to test regularly for ongoing monitoring. How can I find out the optimum amounts and types of sea vegetables to eat?

  • Excellent video.
    Personally I take a daily supplement of 150mcg iodine, since I don’t like adding a lot of extra salt to my meals.
    And I’m staying away from kelp. ;]

  • I have also heard: ‘Iodine for hypothyroidism: like gasoline on a fire?’!/chriskresser/status/115748267156975616 links to studies

  • Are there Iodine only supplements and are they effective to take? Also, is there any vegan supplement that provides 100% DV of B12, D and Iodine all in one for those of us that eat only whole plant based foods?

  • Sheryl

    I’m trying desperately to get my mother to change to a vegan diet because of her heart issues, diabetes and cancer! She is doing really well with it so far, but because she had her thyroid removed many years ago, she’s afraid to eat kale, broccoli or anything in the cabbage family. (iodine related problem I guess)

    My question is…is it true that cabbage family foods need to be avoided for people who are on thyroid medication?

    • Michael Greger M.D.

      There are natural substances in a wide range of healthy foods (including cabbage family vegetables, soy, flax seeds, and a hundred other plant families) that can interfere with thyroid function in those with inadequate iodine intake. The answer isn’t that we should avoid these super-healthy foods, but instead make sure we get enough iodine (the anti-thyroid effects are reversed in iodine deficient individuals with iodine supplementation). See my videos Avoiding Iodine Deficiency and Pregnant vegans at risk for iodine deficiency.

      Now your mom is a special case. The mechanism by which these substances are thought to work is by inhibiting iodine uptake by the thyroid (so this is why if you’re iodine deficient this can be a problem, but if you have enough iodine your thyroid gets all it needs even if you’re eating lots of these healthy foods–though one can overdo it, see Overdosing on Greens). Your mom doesn’t have a thyroid gland, so there should be no effect of cabbage family vegetables since she’s taking pre-made thyroid hormones in pill form.

      • Teresa

        Can the efficacy of the thyroid pills be reduced by consumption of cabbage family vegetables at the same time as taking the pill?

      • Alysson Hartmann

        Appreciate the info. regarding iodine with thyroid issues. I have Hashimoto’s and feel as though everywhere I turn (websites, health “professionals”, etc. the paleo diet is hailed as the best diet for Hashimoto’s and other autoimmune diseases. I would love to hear you do a video debunking that. By the way, your new book has changed my omnivore Nurse Practitioner mother to a plant-based eater! After years of me trying all it took was reading your book. Already she is off her antidepressants and feels wonderful. Thank you!

        • Mery Daae

          Hi Alysson, just been diagnosed myself and Im on a plantbased diet that I would rather not quit. I still dont understand the iodine relationship with this and so. Any tips for me? thanks!

  • LynnCS

    Over the last year I have had a lot of hair falling out, so am taking a supplement for hair growth. I decided to take an iodine supplement based on past experiences of low thyroid and because I eat a lot of greens that are said to interfere with thyroid/iodine function, and also a fair share of sea vegis. Now I am wondering if I am overdoing it. Any ideas? A few years ago I took a 24 hr iodine test and it came out ok. I think I’ll drop the iodine supplements.

  • stacy7272

    My family and I eat lots of beans. I buy Eden Organic beans and I’ve noticed that they all list kombu as an ingredient. Should I stop using this brand?

  • Michael Greger M.D.

    Also be sure to check out my associated blog post Optimum nutrition recommendations!

  • spiegel

    I found the URL to the site of the report featured in your video: it only shows a few people who were affected by consuming soymilk with kombu.  It is unclear whether combining soy with kombu was the problem.  Some researchers would argue that soy consumption could have contributed to the thyroid problem.  I am wondering how many other people who have been consuming just kombu without exhibiting iodine toxicity as reported in the video.

  • striving

    Is one bag (454g) of kelp noodles a day too much?

    • enidcoleslaw86

      I’d also like to know this.

  • Pandabonium

    Actually, Doc, my nearest nuclear power plant DID melt down! (I live about 100 miles south of Fukushima Daiichi). Happily, we were spared dangerous levels of contamination.

    But seriously, this kombu business… How long does iodine stay in the body? I do ingest kombu from time to time, but it is in small amounts, such as when I make vegan dashi soup stock by boiling a bit of kombu and several shitake mushrooms. Once a week? perhaps less? I really don’t think iodine is an issue, even if I get more than enough iodine on one given day. How long is it in my body? A few days?

    As for shijiki… really? Eden foods has posted an excellent English language article about this which sites evidence (by scientists in Ibaraki – my fair prefecture – that the alleged arsenic levels may be due to the acidic compounds used to test for it. And In addition, this is not something we in Japan eat very much of, and not even daily. Perhaps a spoonful with a bento lunch once a week? I don’t know of any reports of actual harm being done to Japanese consumers due to eating small amounts of the stuff. Certainly, the meat and dairy consumed in Japan is a far larger concern, don’t you think?

    As you point out, sea vegetables contain many beneficial nutrients. I don’t over do eating them (as Americans seem to do with many foods) and until hard evidence suggests otherwise will not refrain from consuming them.

    Thank you, with respect and great appreciation for all you do to bring us the latest in scientific knowledge about nutrition.

  • DEE

    Please give me Your opinon on liquId iodine concentrate
    vs levothroxine for thyroid treatment . rx 2 or more drops
    in water per day. or .50mg levothroxine. Have been tested
    t3 t4 tsh. Close to a plant based diet. LOTS OF SYMPTOMS!
    NEITHER seem to help much with symptoms! THANKS

  • anna in JAX

    Dr. Greger, I am reading Kathy Hester’s book “The Great Vegan Bean Book” in which she states that beans in the kidney bean family should be boiled for 10 minutes — including cannellini beans — to rid them of “a toxic agent, phytohaemagglutinin, also known as kidney bean lectin” What does this toxin do? And do you agree with her remedy?

  • vegan minstrel

    Presently taking 1/8th teaspoon of kelp powder from plants grown in an Iceland bay away from shipping lanes. That amount has a bit more than the US RDA. Taking that with an equal amount of chlorella powder to bind any heavy metals which might still be in the kelp. Does that sound legit?

  • Happy

    Eden Black Bean soup has Kombu Seaweed, should we avoid it?

  • Adam

    I’ve heard that soaking kombu in cold water for a few hours, which the prefered way of making dashi, releases virtually no iodine. Is that true? I then thow away the kombu and use this subtle fragrant water to cook beans, soups, gravies and breads. I can’t find any reliable information about this claim and therefore ask for your insight.

  • Bruce Cropley

    Off topic: I’ve been following several of the recommendations on this site for about 2 weeks now (more changes in the pipeline), and I’ve noticed a completely unexpected benefit – my persistent (but minor) tinea has almost disappeared without any ointment, powder, or even cleaning attention. Wow!

    • Jackie

      Which of the things you were doing do you think positively affected your tinea? Thanks.

      • Bruce Cropley

        Sorry, false alarm. It isn’t bad, but it hasn’t gone away completely yet either. I have changed so many things around the same time that it is difficult to know what caused what. But I still think all these dietary changes have been for the better :)

  • Tobias Brown

    Arame appears on the chart as a possible good middle level iodine content seaweed. However, it is a type of kelp according to the wikipedia article. Kelp is shown as dangerous. I’ll search for the source of this chart.

  • Tobias Brown

    Should these journal articles (cited in this video) be more freely available to the public? I found the article on Nutritional Value of Edible Seaweeds but I need to subscribe at $549 US.

  • Tobias Brown

    What is the iodine content of arame? What’s a good amount to consume daily?

  • Tobias Brown

    This guy claims that cranberries contain iodine,
    4 ounces = 400 mcg of iodine. If this is true, cranberries might be easier than seaweed.

    • Joseph Gonzales R.D.

      I am not sure about cranberries and their iodine content. I wrote about sources, here. Yes, I would agree that berries grown away from the coast would have less.

  • Massimo

    I must be one typical example of this situation. Since a few years ago I have high TSH (about 6 to 7 mUI/l, normal is below 4), normal T3 and T4, thyroid ultrasonography normal, no symptom at all…. this year I did a ioduria test (on a 24h urine sample) and the result was 1332 mcg/l (normal is below 300). I used to eat a lot seaweeds, especially during my frequent travels to Japan, I do not see any other possible cause (I’m a long term vegan), so now I’m refraining as much as possible from eating seaweeds and taking essential oils to keep TSH to a more normal level. I do not have any anomaly apart from a somewhat high cholesterol (for a vegan: 1.92 g/l TC, I was between 1.20 and 1.40 before), which is also a known effect of hypothyroidism. Hadn’t I did the TSH test, I would never have suspected something was out of order, having no symptom at all.

  • Blaice

    Out of curiosity. Wouldn’t eating 1/5 a gram or less of dry kombu be perfectly acceptable if that is basically your only source of iodine? I just don’t see an issue with using very, very small amounts as a supplement that will literally almost last your entire life? Am I missing something?

  • Cathy Katin-Grazzini

    Does the common practice of adding a strip of kombu to the pot when cooking up dried beans pose a risk of excessive iodine? (This cooking advice to soften beans and increase digestibility is found on Dr. Weil’s website and many others.)

  • Trevor

    I am making my own seaweed capsules 600mg
    Could someone tell me how much iodine is in 500mg of digitata seaweed?
    It seems from my calculations that this would amount to 2500mcg of iodine.
    I have also heard that 37% goes through the body to waste.

    The average amount in digitata is 0.1-0.3 per 100grams
    Can anyone help?
    Kind regards

  • Leah

    Dear doctors,
    Is there any hope of ever getting off of Levothyroxine for hypothyroidism?

    • Mery Daae

      did you find anything? Thanks!

    • I was taking kelp granules and was able to get off, but I was also eating a whole foods planet based diet (I’m a vegan), no GMOs and pretty much all organic, lots of water, regular moderate exercise, enough sleep, and lots of raw fruits and veggies and healthy fats (from foods plus adding 2 tbsp ground flax to diet each day). I’m still taking kelp granules as I heard that we really don’t get enough iodine and that the DV isn’t high enough. I haven’t experienced any problems but was interested in this video, but was disappointed that nothing at all is mentioned WHY excessive iodine is bad….

  • This video was disappointing as it didn’t explain why high levels of iodine could be bad other than cases of toxicity, but no mention of symptoms, etc.

  • Zuppkko

    After eating kelp for almost 2 years, almost every day, i got slightly hyperactive thyroid. I cannot say for certain that this is from eating kelp, but sure looks like that. We’ll see what tests will show in the future, since i’ve stopped eating the seaweed.

  • Aliena

    I had recently been looking for no-salt added beans. I found Eden Organic products. I checked this site to see if the Kombu source of iodine was okay to consume. After watching that featured video, I am satisfied that I am getting the right amount of iodine from it. Then my father found out that Kombu was added to the beans. He said that powdered Kombu is monosodium glutamate (MSG). I have been steering clear of that neurotoxin my entire life. Do I need to be concerned about products containing Kombu?

    • Thea

      Aliena: Saying powered kombu = MSG does not sound right to me. Kombu is much more than just glutamates. It would have fiber, various phytonutrients, minerals etc. Even if kombu = MSG, I think you might want to check out the NutritionFacts videos on the topic of MSG:

  • Mary

    I have Hashimoto’s and I just started using seaweed flakes instead of salt to make sure I have iodine in my diet. So far this is the only information I’ve found from you that relates to Hashimoto’s. Is there anything else you’ve researched about treating Hashimoto’s and thyroid disease through lifestyle? A lot of what I see online has to do with consuming bone broth to heal a leaky gut… which sounds like pseudoscience to me.

  • Helga_R

    So as I understand, the man has a lot of iodine in his urine wich is not actually a toxicity itself, because he take the most of it away from the body.
    Hi level of iodine in blood – that’s would be bad for him, but if he take 1000 mg and he get it away 950 mg – it’s not the same problem?
    With autist kids they get same situation – kids with near 0 amount of mercury in the hair had a plenty of it in the brain. they just was unable to get rid of it, so those who get bigger amount in the hair was in less dangerous position.

    And another good question is what an actual normal level for us?
    because usual way to find a “normal range” – is just measure “healthy population” and make some statistic from it.
    But what if this population leave in iodine deficiency area?
    you obviously get the lower result then it’s really are normal or good for us.

  • George

    I want to use some kelp power as a source of iodine, the label from the jar says “iodine 920 (cfu/g)”. Does this label make sense to anyone, or it’s just wrong? What does colony-forming unit (cfu) has to do with the quantity of iodine?