Hair Loss and Iodine

Personal update: I have, for all intents and purposes, finished the article on soy that I worked on for over 3 months. But, it is not yet live. I’m hoping it will be soon. In the meantime, I’m getting to the back log that built up during the time I was working on it.

And without further ado, here is some information on hair loss and iodine:

QuasiVegan’s post Hair Loss on the Vegan Diet, brought my attention to the fact that thyroid problems can cause hair loss, something that I was not aware of previously.

I have updated the article, Hair Loss, with the following:

Summary: Occasionally, women who become vegetarian or vegan report experiencing hair loss. If there is a dietary cause, the most likely are rapid weight loss, thyroid problems, or iron deficiency. Zinc deficiency and not getting enough of the amino acid lysine could also be culprits.

According to Mayo Clinic, an overactive or underactive thyroid gland can lead to hair loss. Upon going vegetarian or vegan, people might increase their soy intake. Soy can affect the thyroid, especially when iodine levels are not adequate or someone is predisposed to thyroid problems. Making sure you get enough iodine, by taking 75 to 150 µg per day from a supplement, should prevent any hair loss problems that could be due to iodine or soy. If you are predisposed to thyroid problems, limiting soy might also help.

16 Responses to “Hair Loss and Iodine”

  1. Veganman Says:

    Ah! This explains my Grave’s Disease. Thanks!

  2. Mikki Says:

    I’ve had (yay for the past tense!) thyroid and estrogen receptive breast cancer. I worry about soy intake. Is it safer in any particular form (tempeh, edamame, e.g.)? Does having had thyroid cancer mean I have a thyroid problem or not (I take levoxyl to make up for the fact I don’t have one)?

  3. Jack Norris RD Says:


    Studies have shown that 2 servings a day or less of soy is safe for people who have had breast cancer. The studies have not tested for any differences between different soy foods. You can read more about that at

    Regarding thyroid hormone, if you change the amount of soy you eat, you should talk to your doctor in case your prescription needs to be adjusted. Other than that, it should be safe for you to eat.

  4. Mikki Says:

    Thanks for this. What do you mean “if you change the amount of soy you eat”? What amount of change requires talking to my endocrinologist? It’s beginning to sound like too much trouble, and I may have to give up eating soy, which I love and which I eat in varying amounts all the time. This makes me sad.

  5. Jack Norris RD Says:

    > What do you mean “if you change the amount of soy you eat”?

    My understanding, and I’m not an expert, is that people on thyroid hormone should eat similar amounts of soy each day to keep their isoflavone levels stable. If you go from, say, 2 servings a day to 4 servings a day, you might want to check with your doctor to see if he/she wants to test to see if you need your thyroid hormone amount adjusted. I am not sure if having your thyroid removed changes this scenario at all.

  6. Jesse Says:

    I’ve read that vegetarians often have iodine deficiency, to a large degree because they shop at health food stores and buy sea salt without added iodine. So I make sure to use iodized salt…

  7. No More Says:

    I knew about this years ago, but it was too late. Soy already destroyed my health from 9 years of daily ingesting. Hair loss, weight gain, fatigue, loss of memory, IBS, inflammation of the intestines, etc. Stop eating it in excess before it’s too late for you too. Some people have genes that produce enzymes to digest this stuff. Others do not.

  8. Jack Norris RD Says:

    No More,

    If you really had this experience and are not merely an anti-soy internet troll, I’d like to hear more about it and why you think all of these problems were attributable to soy rather than non-diet-related thyroid problems. Were you getting enough iodine? How much soy were you eating?

    As I describe in Soy: What’s the Harm?, 14 clinical trials show soy to be safe for the thyroid.

    I’ve also never heard of an enzyme needed to specifically digest soy – which enzyme are you referring to?

  9. Christina Arasmo Beymer Says:

    One more time, but with feeling:

    @No More,

    All the symptoms you attributed to soy are the symptoms of hypothyroidism: sluggishness, brain fog, hair loss, and weight gain.

  10. Dan Says:

    Hi Jack,

    Since you seem to be the receptacle/repository/recipient of all manner of health concerns from vegans, vegetarians (and maybe omnivores?), here goes another….

    I’ve noticed, really for the first time in my life, that my hair seems to be really thin, dry and frizzy. I have not noticed any hair loss per se, just that my hair appears to have gone from a thick, combination profile (oily) to really dry, split ends and frizzy. I went fully vegan in the summer. Don’t think it’s iodine (supplementing every day). Could it be lysine or zinc or DHA? If the latter, it should get better soon, since I’ve decided to restart my DHA 250 mg o.d. supplement. Main sources of protein in my diet are nuts and seeds, peanut butter, very limited grain and smallish amount of beans (about 1/2 cup per day). I am going to increase my beans and grains. Would you consider taking a low dose Zn supplement too? I haven’t had a cold in a very long time although I did have two severe GI bugs this year. If this is a Zinc issue, I’d like to catch it early.

    Thanks for your help!


  11. Jack Norris RD Says:


    I don’t have any idea what could cause your hair to be thin, dry and frizzy. I’d say low-fat due to the dryness but it appears you are eating plenty of fat. Trying some zinc for a few months might not hurt. Have you checked into biotin? That seems to have more to do with hair loss than what you’re experience, but here’s a link:

    It might just be age, though. Or all the worrying you do about DHA. 🙂

  12. Dan Says:


    Thanks for the information! I am not too worried about DHA any more, now that I have seen rhesus monkey studies showed impaired vision in offspring of DHA-deprived mothers. Also there is this, from ….

    5.3. Memory and Learning

    DHA is investigated for its role in memory formation as higher serum DHA concentrations are correlated with greater verbal fluency skills in older humans[154] and a deficiency of DHA is known to damage rat memory processing.

    For animal models, administration of DHA (300mg/kg is the standard dose) appears to promote cognition with improvements noted in reference memory (without affecting working memory) in otherwise healthy rats.[155]

    One study conducted in otherwise healthy young (18-25) persons noted that, after 6 months of supplementation with 2g Lovaza (750mg DHA; 930mg EPA) that working memory was enhanced as assessed by a verbal n-back test (with improvements in 3-back but not 1 or 2-back); this was deemed to be independent of dopamine metabolism but instead correlated with the EPA and DHA content or Red Blood Cells (RBCs; up 75% from 2.9+/-1.0% for DHA, and up 350% from 0.4+/-0.1 for EPA) when looking at the RBCs of persons low in DHA.[156] Elsewhere, youth who have low dietary intake of fish have experienced improved memory retention and reaction time with supplemental DHA at 1,160mg over 6 months.[157] Some isolated studies not reporting dietary intake of fish oil also report benefits to memory formation (as well as attention and reaction time).[158] Interventions in older adults tend to note benefit in persons with[159] and without[160] apparent cognitive decline.

    Some studies fail to find a significant benefit of fish oil supplementation on cognition in healthy adults (400-1,800mg EPA+DHA,[161] 1,400mg EPA and 800mg DHA,[162] or 1g EPA+DHA over 12 weeks[163]) with one of these studies[162] having an exclusion criteria of ‘no more than once weekly’ for fish intake but otherwise diet was not reported.

  13. Melinda Says:

    Any updates on hair loss? I’ve been plantbased for a year now and my hair is getting thinner and thinner. Scalp is visible. All blood work is normal. Distressing.

  14. Jack Norris RD Says:


    I’m sorry to hear about your thinning hair. I don’t have any updates, but haven’t had a chance to research it. I’d recommend getting individual nutrition counseling from an RD who is veg-friendly and would have time to spend looking at your diet and researching the issue in more depth. You can find a list of them here:

  15. Mikki Aronoff Says:

    I had hair loss (thyroid ca, estrogen receptive breast ca). Biotene seems to have pretty much stopped the loss in its tracks. Nothing too appreciable for a few years now, although I’m 75 now and am expecting some “depreciation.”

  16. Bean Says:

    I have a few vegan friends whose hair thinned after going vegan (previously vegetarian). At a vegan festival a few years ago, I was sitting in a lecture and noticed more than a few young women with very thin hair (could see their scalps). Seems more than just a coincidence. Fortunately, I have had no issues myself.

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