Iodine- it’s not just about the thyroid

Iodine is an micromineral which is essential for health and is most strongly associated with thyroid function. Epidemiology suggests that 2 billion individuals worldwide have insufficient iodine intake, with those in south Asia and sub-Saharan Africa particularly affected.1

The thyroid is an endocrine gland located at the base of the throat which is responsible for producing the thyroid hormones T4 and T3. T4 is produced from a molecule of tyrosine and four iodine molecules, it can then be converted to T3 (1 tyrosine and 3 iodine molecules), incidentally zinc and selenium are also required as cofactors for its production. Thyroid hormone controls metabolic rate of all body cells and therefore elicits an effect on all tissues within the body. Because of this iodine is considered essential for normal growth and development of body tissues particularly including nerve, bone, reproductive systems as well as hair, skin and nails.2

Deficient levels of iodine contribute to suboptimal thyroid function leading to adverse effects on growth and development and it is thought that iodine deficiency is the most common cause of preventable mental impairment worldwide.1

When iodine intake is insufficient, or deficient, there is a knock-on effect on thyroid hormone production. The thyroid governs the metabolic rate of every cell in the body, therefore suboptimal thyroid hormone production can have a significant, detrimental influence on multiple aspects of health.3

This article looks at the wider reaching effects of iodine deficiency, both related to the thyroid and independent of it.

The richest natural sources of iodine con from ocean life, fish, shellfish, and seaweed, meaning that those who do not consume foods from the ocean, and particularly communities who reside far inland, are at a greater risk of iodine deficiency. This has led to the widespread use of iodized salt, where table salt is fortified with iodine and has reduced iodine deficiency, although this comes with a caveat. Many authorities feel that iodized salt is overused and additionally can contain other products such as aluminium and unnecessary chemicals. It is therefore preferable to obtain iodine from natural sources. Kelp in particular is rich in iodine and other mineral but low in sodium and is a good seasoning substitute for salt.2

As mentioned, the most affected organ by iodine deficiency is the thyroid.  Severe iodine deficiency causes goitre and hypothyroidism because, despite an increase in thyroid activity to maximise iodine uptake and recycling, iodine concentrations are still too low to enable adequate production of thyroid hormone. In mild-to-moderate iodine deficiency, increased thyroid activity can compensate for low iodine intake and maintain euthyroidism (balanced or normal thyroid funciton) in most individuals, but at a price: chronic thyroid stimulation results in an increase in the prevalence of toxic nodular goitre and hyperthyroidism in susceptible individuals, particularly following normalised or increased iodine intake.1

One population which seems to be particularly vulnerable to iodine deficiency is expectant mothers and babies. Adequate thyroid hormone is critically important for normal growth and neurodevelopment in foetal life, infancy, and childhood. Severe iodine deficiency during development results in maternal and foetal hypothyroidism and associated serious adverse health effects, including cretinism and growth retardation as well as miscarriage and stillbirth.3,4 Hence, optimal levels of iodine during pregnancy (200-220ug/day) is essential.

However, it is important not to exceed the safe upper tolerable limit of iodine during pregnancy (1100ug/day, although some research suggest 500ug is too much), as think is linked to thyroid dysfunction in offspring. The mechanisms for this are not fully understood but likely due to alteration is iodine uptake by the thyroid in presence of too little or excessive iodine.5

Additionally, research has demonstrated that iodine is protective for the development of breast cancer. Seaweed is a popular dietary component in Japan and a rich source of both of iodine and selenium. It was thought that this dietary preference may be associated with the low incidence of benign and malignant breast disease in Japanese women.6

It has been demonstrated that the thyroid coverts, or organifies, Iodine into anti-proliferative molecules known as iodolipids. It has been suggested that these iodolipids may also play a role in the proliferative control of tissues outside of the thyroid. Most research support the use of iodine in combination with selenium (another mineral utilised in thyroid hormone production) as selenium acts synergistically with iodine. All three mono-deiodinase enzymes are selenium-dependent and are involved in thyroid hormone regulation. In this way selenium status may affect both thyroid hormone homeostasis and iodine availability.6

Many studies have shown that iodine possess anti-proliferative and anti-neoplastic properties in iodine sensitive tissues including thyroid, mammary and prostate tissue.7-9

  • In animal and human studies, iodine administration has been shown to cause regression of both iodine-deficient goitre and benign pathological breast tissue.
  • In animal and human studies, molecular iodine supplementation exerts a suppressive effect on the development and size of both benign and cancer neoplasia.
  • Clinical trials have revealed that iodine has beneficial effects in fibrocystic breast disease and in cyclic mastalgia
  • Iodine acts as an antioxidant and prevents lipoperoxidation in various organs, including the brain.

Although the mechanisms of action have not been fully elucidated, it is most likely that mitochondrial-mediated apoptosis pathways are involved as previously described for iodine and iodolactones. Studies have demonstrated that iodine exposure to mitochondria isolated from breast tumour tissue causes swelling and organification of the mitochondrial proteins, and release of apoptogenic effectors from mitochondria that cause nuclear fragmentation. Therefore, it appears that iodine may initiate apoptosis by elucidating effects on mitochondrial proteins, leading to anti-proliferative and cytotoxic properties which has been seen in breast cancer cells.6,10

Studies investigating the effect of iodine of breast health have shown9,10

  • Iodine treatment of patients with benign breast disease led to a bilateral reduction in breast size and a remission of disease symptoms, which was not observed when iodide was administered
  • An iodine-deficient state has shown to render the thyroid and the breast susceptible to physiological changes and leads to atypia, dysplasia, and hyperplasia.

Excess iodine consumption has provided conflicting evidence when it comes to issues regarding excess intake. Epidemiological studies show that in iodine deficient population, when iodine intake was normalised, with the introduction of iodized salt, there was an increased occurrence of hyperthyroidism (iodine induced hyperthyroidism IIH). However, many of these incidents did not last longer than two years, again possibly as they thyroid adjusted iodine uptake to account for iodine availability. It is additionally hypothesised that perhaps there were the presence of autoimmune hyperthyroidism (Grave’s disease) which was masked by deficient levels of iodine. In general Iodine-induced hyperthyroidism and other adverse effects can be almost entirely avoided by adequate and sustained quality control and monitoring of iodine supplementation which should also confirm adequate iodine intake. However, it is still recommended to maintain intake below 1100mg/day.12

It is also important to note that iodine is a halogen and is therefore in same group and fluorine or fluoride, present in water as well as toothpaste. Iodine and fluoride can compete for absorption as they have a very similar structure. Therefore, adequate levels of iodine can protect against fluoride toxicity. However, it is also important to be aware that excessive fluoride intake can inhibitor reduce iodine absorption. Fluoride inhibits the ability of the thyroid gland to concentrate iodine and research has shown that fluoride is much more toxic to the body when there is iodine deficiency present.13

Key Takeaways

  • Iodine is essential for the production of thyroid hormone, which controls metabolic rate of all body cells, and therefore elicits effects on all body tissues.
  • Deficient levels of iodine are associated with hypothyroidism, as well as poor development and growth
  • Adequate thyroid hormone is critically important for normal growth and neurodevelopment in foetal life, infancy, and childhood. Severe iodine deficiency during development results in maternal and foetal hypothyroidism and associated serious adverse health effects, including cretinism and growth retardation as well as miscarriage and stillbirth. Hence, optimal levels of iodine during pregnancy (200-220ug/day) is essential, however pregnant women should not exceed intake of 500ug/day
  • Iodine has also been shown to possess antiproliferative and cytotoxic properties and therefore has supportive research in prevention of cancer, particularly of the breast.
  • In animal and human studies, iodine administration has been shown to cause regression of both iodine-deficient goitre and benign pathological breast tissue and has beneficial effects in fibrocystic breast disease (4) and in cyclic mastalgia
  • Some research suggests that excess iodine intake can contribute to hyperthyroidism (iodine induce hyperthyroidism), however continuous normal iodine intake can avoid this. Although intake should not exceed 1000ug/day


  1. Zimmermann MB, Jooste PL, Pandav CS. Iodine-deficiency disorders. Lancet. 2008 Oct 4;372(9645):1251-62. doi: 10.1016/S0140-6736(08)61005-3. PMID: 18676011.
  2. Haas, EM (2006) ‘Staying Healthy with Nutrition’, Celestial-Arts
  3. Pearce EN, Lazarus JH, Moreno-Reyes R, Zimmermann MB. Consequences of iodine deficiency and excess in pregnant women: an overview of current knowns and unknowns. Am J Clin Nutr. 2016 Sep;104 Suppl 3(Suppl 3):918S-23S. doi: 10.3945/ajcn.115.110429. Epub 2016 Aug 17. PMID: 27534632; PMCID: PMC5004501.
  4. Adams JB, Sorenson JC, Pollard EL, Kirby JK, Audhya T. Evidence-Based Recommendations for an Optimal Prenatal Supplement for Women in the U.S., Part Two: Minerals. Nutrients. 2021;13(6):1849. Published 2021 May 28. doi:10.3390/nu13061849
  6. Aceves, C., Anguiano, B. & Delgado, G. Is Iodine A Gatekeeper of the Integrity of the Mammary Gland?. J Mammary Gland Biol Neoplasia10, 189–196 (2005).
  7. Rösner H, Möller W, Groebner S, Torremante P. Antiproliferative/cytotoxic effects of molecular iodine, povidone-iodine and Lugol’s solution in different human carcinoma cell lines. Oncol Lett. 2016 Sep;12(3):2159-2162. doi: 10.3892/ol.2016.4811. Epub 2016 Jul 5. PMID: 27602156; PMCID: PMC4998524.
  8. Arroyo-Helguera O, Anguiano B, Delgado G, Aceves C. Uptake and antiproliferative effect of molecular iodine in the MCF-7 breast cancer cell line. Endocr Relat Cancer. 2006 Dec;13(4):1147-58. doi: 10.1677/erc.1.01250. PMID: 17158760.
  9. Shrivastava A, Tiwari M, Sinha RA, Kumar A, Balapure AK, Bajpai VK, Sharma R, Mitra K, Tandon A, Godbole MM. Molecular iodine induces caspase-independent apoptosis in human breast carcinoma cells involving the mitochondria-mediated pathway. J Biol Chem. 2006 Jul 14;281(28):19762-71. doi: 10.1074/jbc.M600746200. Epub 2006 May 5. PMID: 16679319.
  10. Cann SA, van Netten JP, van Netten C. Hypothesis: iodine, selenium and the development of breast cancer. Cancer Causes Control. 2000 Feb;11(2):121-7. doi: 10.1023/a:1008925301459. PMID: 10710195.
  11. Pearce EN, Lazarus JH, Moreno-Reyes R, Zimmermann MB. Consequences of iodine deficiency and excess in pregnant women: an overview of current knowns and unknowns. Am J Clin Nutr. 2016 Sep;104 Suppl 3(Suppl 3):918S-23S. doi: 10.3945/ajcn.115.110429. Epub 2016 Aug 17. PMID: 27534632; PMCID: PMC5004501.
  12. Delange F, Lecomte P. Iodine supplementation: benefits outweigh risks. Drug Saf. 2000 Feb;22(2):89-95. doi: 10.2165/00002018-200022020-00001. PMID: 10672891.
  13. David Brownstein, Iodine, Why You Need It, Why You Can’t Live Without It

Last updated on 22nd February 2022 by cytoffice


29 thoughts on “Iodine- it’s not just about the thyroid

  1. Good article. I had benign breast lumps and my go told me to put a dab of iodine on each one every morning. It has definitely reduced them.

  2. Great article with widely unknown facts of the benefits of iron for most of the people! I worked with a GP and he made his patients putting some liquid iron daily on the wrists when they had their first signs of a cold. I observed that the cold just disappeared within 24 hours.
    Could you have included the different iron products we find on the markets? I believe that iron containing alcohol (almost all do) are not beneficial. Good iron isn’t that easy to get.

    1. Hi Hermine – This blog was in relation to iodine not iron. It is important to only supplement iron if you know you have additional requirement. I am unaware of this method and has not been substantiated by research but very interesting thank you.

      1. So sorry! Of course I meant Iodine not iron. Iodine is helping when first signs of cold appear. Thank you for your response.

  3. I have an under active thyroid and have been prescribed Levothyroxine. The 25 rate does nothing and the 50 rate I appear to get a reaction. Nothing in between. I have just started to take your thyroid support can you please confirm I do not need additional iodine and should I be taking two per day please

    1. Hi Anne – The Thyroid support contains kelp providing 150ug per capsule so you do not need to supplement additional kelp on top.

  4. Thanks for the article and references. I’ve just been investigating this for helping manage sub clinical hypothyroidism / M.E and a low grade long standing fungal infection that happened when I got a virus and subsequently ‘leaky gut’. TBH the main reason I’m taking it is to resolve my gut issues and the fact I can’t even look at something sugary without my gut going mental! (Despite my rigid AIP diet and zero refined sugar and low carb etc) I’ve learnt alot from Dr Sarah Myhill on the uses of Lugol’s Iodine and just took my first dose last night. Be interested to know of anyone else’s experience with this and effectiveness……

  5. I have read this article with interest as I have an overactive thyroid and have been taking carbimazole to control it for 10 years now. I was told by the endocrinologist at the time of diagnosis to avoid iodine supplements and foods such as kelp. I have avoided taking ‘multi’ supplements as they contain iodine. would the amount of iodine in the ‘multi’ supplements be safe for me to take?

    1. Hi Cherry – Levels of iodine in our multi vitamins and minerals are well within safe levels, however I would recommend you discuss this with your endocrinologist. Thanks, Helen

  6. Whenever I’ve been lacklustre in mood and sluggish in body, a short course of seaweed kelp supplements have helped to ‘kickstart’ my metabolism and mood, so much so that I’ve got increased vigour, get up and go and my excess weight has gradually fallen away to return to my energetic ‘wiry’ self. When I was younger (in the 1970’s and 1980’s), we used to eat a lot of local Lavabread (seaweed) which was of course, a better, more natural form of iodine. I was always full of energy and my metabolism was athletic standard! I However, I’m nearly 60 now and am finding that the seaweed supplements in say, Holland & Barrett or Boots chemist, do little to nil in terms of the benefits of kelp iodine from my former times. I feel drained, mentally and physically most of the time these days and I’m leaning towards a good source of iodine but why is your product better? Hope you can help me.

    1. Thank you for your comment. As I have no details on the other sources of kelp I’m afraid I cannot make a direct comparison. However, our kelp is guaranteed 280ug of iodine and is from organic sources produced in the outer Hebrides so if form very clean marine source. I would recommend trying this first, failing that you could try 2 x Thyroid Support. Thanks, Helen

  7. Thank you for this information – definately one to watch out for with there being links to breast & prostate disease.

  8. Interesting article but I thought from previous correspondence that Cytoplan had agreed not to endorse the referencing of animal experiments? This barbaric, unnecessary and arguably unscientific face of science is not acceptable and should not be promoted as such. If scientists did what they do to animals in labs *outside* of labs they would be prosecuted by the RSPCA for animal cruelty. Food for thought.

    In this article there were references to animal experiments, mainly involving rats and mice. As in many such articles the grisly details are not overt, but just follow the references and you will find them.

    Did you know, for example, that in order to see whether mice with ‘breast cancer’ are helped by the addition of iodine to the diets — one of the studies quoted in the article above — they have first to be injected with a carcinogen to create ‘breast cancer’? In another of the experiments it says that “At the end of the experiment the rats from each group were sacrificed by decapitation.” And we think we live in a civilised society?

    We do not need to torture animals and I would argue that we should not. Increasingly, and very much in the news lately, animals are being recognised as sentient. (Amazing that it took so long for scientists to acknowledge this; any sensible person with an ounce of awareness and empathy could tell you that!)

    Today there are many alternative ways of conducting research including in vitro testing, nature-identical tissue testing, computer modelling, and most relevant of all, human studies.

    Please, Cytoplan, vet your authors’ contributions more carefully for references to animal experiments or better still give them House Content & Style Guidelines. Thank you for taking the time to read this.

    1. Hi Lindsey – Thank you for your feedback. All references cited are either review paper, epidemiological or have used human cell lines and are not themselves animal studies, although appreciate some have cited animal studies as support for their own study. We do not endorse them but also have a responsibility to source robust research, most research at some point will have come from an animal study. We have not directly cited animal studies.

  9. It’s great to hear that iodine is back in the good books. We, as a family, have been taking nascent iodine for about 5 years now and agree that it’s health benefits are amazing! It not only pushes out toxic halogens from the thyroid, it boosts the health of other organs, especially the breasts. I would never be without iodine. The book called ‘The Iodine Crisis’ is a good read and very informative.

    1. Hi There – headaches can be so multifactorial, with any number of nutrient deficiencies potentially contributing to their occurrence. They may also be related to hormonal fluctuations, blood sugar imbalances or musculoskeletal issues – to name but a few. It would be useful for us to get a little more information in order to make some personalised suggestions for you – please complete our online health questionnaire and one of our Nutritional Therapists will come back to you shortly.

  10. I have often read about the importance of testing iodine levels before supplementing in case it is not needed. I am not a health professional.

  11. In your article your measurements were rather too scientific for me. Would you please explain how ug/day could be expressed in drops/day?
    Thank you

    1. Hi there – I’m afraid we don’t do a liquid iodine supplement so wouldn’t be able to advise on this. Our Organic Kelp provides 280 micrograms of iodine, and we would recommend you took one capsule daily. If you are looking specifically to support thyroid health we would instead recommend our Thyroid Support supplement which provides iodine, as well as several other nutrients needed for thyroid hormone production. The dose for this supplement is 1-2 daily – but please do note that we don’t recommend it is taken alongside levothyroxine.

  12. Thanks for this informative article. How does one get their iodine levels tested? I live in Spain and it does not appear to be offered by GPS here

    1. HI There – I’m afraid I’m not aware of testing available in Spain, but one would assume that you would be able to get a thyroid function test through your doctor? Iodine is one of the most common mineral deficiencies, so if you are displaying and signs of poor thyroid function then our Thyroid Support may be supportive – provided that you aren’t taking prescribed thyroid medication.

  13. Hi I’m on 100 mg levothyroxine . I’ve had underactive thyroid for over 20 years & it runs in the family
    My hair still falls out & v dry . I wake up during the night . Dry skin etc
    Would you suggest iodine or thyroid support ? I’m about to have a blood test to check levels

    1. Hi There – it would be great to get a really thorough picture of your health profile, including diet and lifestyle, so we can make some tailored recommendations. Once you have received your test results, do please complete our online health questionnaire and one of out nutrition team will come back to you – Tailored Health Questionnaire | Cytoplan

  14. I have read on that you should not supplement with iodine if you are already taking thyroid medication? e.g. Levothyroxine.

    1. We do recommend that if you are taking Levothyroxine you should consult with your doctor before taking our Organic Kelp (a rich source of iodine) – but the level of iodine (from kelp) in our multivitamins is akin to a healthy diet and therefore, in most cases, can be taken with Levothyroxine – but always check with your GP if you are unsure.

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