Doctor's Note

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.

Check out my associated blog posts: The Best Detox, Optimum Nutrition RecommendationsDo Eden Beans Have Too Much Iodine?, and The Best Way to Prevent the Common Cold?

  • 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.

    • Lachicavegana Comefrutas

      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?

  • 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.

  • 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:

  • radhasahar

    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?

  • Cyclo Uten Etternavn

    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. ;]

  • Lance Strish

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

  • Scott Beavers

    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?

  • 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?

  • 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 :)