Iodine in Vegans

Just updated the Iodine page at VeganHealth.org. The important new info (thanks, Lisa!) is this study:

In a 2011 cross-sectional study from the Boston area, urinary iodine levels of 78 lacto-ovo vegetarians and 62 vegans were measured (1). People with previously diagnosed thyroid problems were excluded from the study. According to the authors, “Population iodine sufficiency is defined by median urinary iodine concentrations 100 µg/l or greater in adults and 150 µg/l or greater in pregnancy.” Median urinary iodine concentration of vegans (79 µg/l; range 7 – 965 µg/l) was significantly lower than vegetarians (147 µg/l; range 9 – 779 µg/l). Markers of thyroid function were similar in both groups and in the normal range; one vegan and no vegetarians had abnormal thyroid function. Most of the vegans were making no effort to insure adequate iodine intake.

So, it appears that vegans have not yet gotten the message about the importance of iodine (or most are not taking heed). It’s a good thing that only one showed abnormal thyroid function given how low the average was.

My recommendations are to take 75 to 150 µg of iodine every few days.

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Reference

1. Leung AM, Lamar A, He X, Braverman LE, Pearce EN. Iodine Status and Thyroid Function of Boston-Area Vegetarians and Vegans. J Clin Endocrinol Metab. 2011 May 25. [Epub ahead of print] Link

25 Responses to “Iodine in Vegans”

  1. Madeleine Says:

    You could also just eat seaweeds such as dulse, nori & wakame as a regular part of the diet. Not only is one getting the iodine but other trace minerals.

  2. Jon Says:

    I throw dulse in my morning smoothie and put it on all my stir-fry meals.

  3. Jean Says:

    The study does not mention the ages of the individuals. When hormone levels drop drastically, particularly at menopause in women and andropause in men and those approaching middle-age, the thyroid requires much more iodine no matter what your diet. I have been vegetarian 45 years and vegan 21 years.
    I assumed I would be fine throughout this physical change that happens to everyone. I choose not to go on any medication, especially from animal products. I take three forms of iodine twice a day. My thinning hair is thick again.

  4. Jack Norris RD Says:

    > The study does not mention the ages of the individuals.

    They were adults aged 18 and older, with an average age of the vegans of 36 (standard deviation of 13 years).

    Note that there is an upper limit for iodine intake of 900 mcg for adults.

  5. New Iodine Info from Jack Norris Says:

    […] Norris, RD just updated his iodine page, based on a worrisome new study indicating that many vegans have inadequate iodine levels. Non-pregnant adults should be over 100 […]

  6. NuVegan.com » Blog Archive » New Iodine Info from Jack Norris Says:

    […] Norris, RD just updated his iodine page, based on a worrisome new study indicating that many vegans have inadequate iodine levels. Non-pregnant adults should be over 100 […]

  7. RespuestasVeganas.Org Says:

    Thanks for the information.

    Solution: iodized salt.

    Regards,
    David.

  8. Elaine Vigneault Says:

    I’m confused. If the “markers of thyroid function were similar in both groups and in the normal range” then what exactly is the problem? I repeat, “in the normal range.”

    What you have is evidence that vegans pee out less iodine than nonvegans. That’s not evidence that vegans consume less. That’s not evidence that vegans don’t consume enough. That’s not evidence of anything, really, except that vegans _in this study_ pee out less iodine than nonvegans.

    Again, what’s teh problem here???

  9. Jack Norris RD Says:

    Elaine,

    > That’s not evidence that vegans consume less.

    I’m pretty sure that’s what it means. Iodine is not stored to any great extent and so urinary iodine is a way to measure intake.

    That said, there is not necessarily a problem here, but there might be.

    It was a cross-sectional study and anyone who was previously diagnosed with thyroid problems were excluded. So if a vegan had gotten a thyroid problem from iodine deficiency, they would not be included. I would assume that a safe level for a population is considered above 100 µg/l for a reason, but maybe they are being very conservative, I’m not sure and haven’t studied how they came up with that level. But someone who has a level much lower than 100 µg/l should definitely be concerned. At least, I wouldn’t want my iodine that low – it’s not worth the risks.

  10. jj Says:

    hi Jack, is it adequate in your opinion to rely on iodized table salt? As a Canadian I’ve been consuming it all my life — I add it to many meals (am trying to cut back, really, as I’m a salt-aholic!).

  11. Jack Norris RD Says:

    jj,

    In the U.S. iodized salt is iodized at a rate of 75 mcg per 1/4 teaspoon of salt. I don’t know how much iodine is in Canadian iodized salt. 75 mcg per day should be enough iodine. But you should only rely on it if you are eating that much and the salt is iodized at that rate (or higher).

  12. Mike Says:

    So any idea what the cause is? Are vegans avoiding iodized salt for sea salt and thus not getting the required amount?

    I’d be curious to see the general population’s iodine levels…

    -Mike

  13. Jack Norris RD Says:

    Mike,

    A lot of vegans probably don’t salt their foods, and only table salt is iodized (salt in commercially produced products isn’t iodized). Nor is sea salt iodized.

  14. Elaine Says:

    Thanks for responding. Sorry if my skepticism comes off as criticism. That’s not my intent. I’m genuinely curious about iodine. I’m also biased against scare-mongering because it tends to result in people running out to “health food stores” to buy more bottles of vitamin pills of whatever is the hot new micronutrient of the day without taking a more holistic approach and simply eating and living more healthfully. I see far too many vegans and anti-vegans get caught up in the details and lose sight of the big picture.

    You’ve written yourself that vegans tend to live just as long and healthy lives as nonvegans so I’m not sure why you would make rash generalizations like “vegans have not yet gotten the message about the importance of iodine” if there’s no actual evidence that this one small study of vegans’ pee indicates any actual ill health. To me, this study seems to show the opposite: that higher iodine intake may not be as important to thrypoid function as some people thought. Is there any other study that indicates vegans, in general, have a higher incidence of thyroid problems than nonvegans?

    On Wikipedia it says that “The thyroid gland needs no more than 70 micrograms /day” and that additional iodine is necessary for “optimal health” of other things like gastric mucosa, salivary glands, and more. As wikipedia is generally about 98-99% accurate and since there are sources cited for this claim, I think it makes sense to be a bit skeptical of any claim that vegans are putting their thyroid health at risk unless they pay super close attention to their iodine intake.

    The overall message I get from a lot of what you write is that being vegan is difficult. I know that’s not your intent, and in fact you intend to make being vegan easier for people, but that’s how it feels to me.

  15. Jack Norris RD Says:

    Elaine,

    > You’ve written yourself that vegans tend to live just as long and healthy lives as nonvegans

    I’ve written that their mortality rates appear to be the same as regular meat-eaters, though it would be nice if we had at least somewhat more data to determine this. Right now, it’s based on about 760 vegans, which isn’t many.

    I don’t think we should allow that finding to make us complacent. I hear from vegans from time to time (multiple times per year) who have thyroid issues arise.

    > The overall message I get from a lot of what you write is that being vegan is difficult.

    Unfortunately, when you argue with me, I start to sound even more like I think being vegan is difficult, because I have to justify my recommendations or caution.

    For the record, I don’t find being vegan difficult. But I take B12 and I take iodine and calcium. I take vitamin D if I’m not getting any sun. I pay attention to omega-3s. And I think it’s pretty much a breeze to be vegan. But if I didn’t take B12, iodine, calcium or vitamin D, I might find, over time, that being vegan isn’t as easy (because my health might deteriorate).

    > super close attention to their iodine intake.

    I think there is a difference between what I’m saying, which is “make sure you have a regular, reliable source of iodine” and “pay super close attention.” I didn’t suggest anyone run out and get their thyroid hormone tested or their urinary iodine levels tested. I’m just saying “pay some attention to it”, not “pay super close attention”.

    For the people in that study with urinary iodine levels slightly under 100, they may very well be fine. But there were some vegans with much lower levels. They do need to be concerned and could find themselves in trouble at some point. I think the chances of that happening are quite possible and it would be worse for spreading veganism than my suggestion that vegans need to take heed of the advice to pay attention to iodine intake.

    > Is there any other study that indicates vegans, in general, have a higher incidence of thyroid problems than nonvegans?

    This is the only one I know of that measured thyroid hormone (besides the current study we are discussing of U.S. vegans): this page.

  16. Being Picky About Vegan Nutrition | The Vegan RD Says:

    […] published just weeks after that conversation found that U.S. vegans may be at risk for suboptimal iodine status. Some omnivores get iodine from fish, but most Americans get it from iodized salt and from dairy […]

  17. Elaine Says:

    That link doesn’t work.

  18. Jack Norris RD Says:

    Sorry. Fixed.

  19. Elaine Vigneault Says:

    That study you linked to is intersting because in that study, they said “It was concluded that use of kelp can be associated with raised thyroid stimulating hormone”. In other words, they concluded that most vegans were fine but the few who weren’t were more likely to have iodine intakes that were too high, not too low. So now, we have two small studies about vegans and idodine and the studies’ evidence contradicts one another. Fantastic.

  20. Jack Norris RD Says:

    Elaine

    > they concluded that most vegans were fine but the few who weren’t were more likely to have iodine intakes that were too high, not too low.

    They’re actual conclusion is this:

    “It is conceivable that our sample of vegans included subjects with slightly raised concentrations of thyroid stimulating hormone because of a low intake of iodine, as well as subjects with markedly raised concentrations of the same hormone because of excessive intake of iodine.”

    Two of the vegans who were not eating kelp had elevated TSH in the “subclinical hypthyroidism” range, while none of the omnivores did. But that is only two out of 48, a small pecentage of vegans. I’m not suggesting that most vegans who do not take iodine have thyroid problems, just that it’s a possibility that is great enough to warrant making sure that you get enough iodine.

  21. Derek Says:

    on your iodine page you say “North American vegans should take a modest iodine supplement; 75-150 µg every day or every other day should be enough” but here it’s 75-150 every 2-3 days

  22. Jack Norris RD Says:

    Derek,

    I changed it everywhere to “75-150 µg every few days.” Thanks for catching the discrepancy.

  23. Ayla Says:

    Hi Jack, after reading your text on iodine a few months ago we changed our regular table salt to iodised salt. However, I recently discovered that the salt in Dutch and Belgium bread is already iodised. Due to the high amounts of salt in our bread, 4-6 slices of bread per day (which is pretty standard in our culture) already brings us to slightly more than 150 µg per day so supplementing isn’t necessary. Thought you might find this interesting in case you ever run into a Dutch or Belgian client.

  24. Dharma Says:

    Jack Norris, thanks! i am taking levotiroxine, do i need no iodine? o is it necesiary for anoother function?

  25. Jack Norris RD Says:

    Dharma,

    I don’t know–you should ask your doctor to be sure.

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