Iodine: a wonder-nutrient for cancer?
What do you know about iodine? If you are anything like the typical person the chances are you know very little. Whilst most people are vaguely aware that iodine is something we all need and that seafood is a good source, knowledge beyond that is generally hazy when it comes to this essential mineral.
Whilst the details of iodine remain unknown to the average lay person, this nutrient has been the focus of much attention within the nutrition community due to its vital role in health and the prevalence of deficiency. Scientists have long been aware that iodine deficiency leads to low thyroid function (hypothyroidism) and that hypothyroidism in young infants due to insufficient iodine is the leading cause of preventable intellectual disability in the world. This has made iodine deficiency a public health problem of serious concern and in various parts of the world iodine fortification (e.g. adding iodine to table salt) has been implemented in order to address the problem. These programmes have generally been successful resulting in improved thyroid function and decreased incidence of goiter (enlarged thyroid gland sometimes caused by iodine deficiency). But although iodine deficiency is now less of a problem worldwide, there are areas; including parts of Europe that still have a problem. UK diets were generally thought to provide sufficient iodine until relatively new research has shown this may not be the case. For example a 2001 study involving around 700 teenage girls found that two-thirds of the girls were mild-to-moderately iodine deficient and that a small number had very low levels1. Concern amongst UK experts has led to the formation of the UK Iodine Group; a group of scientists on a mission to promote awareness of the importance of iodine in the diet and to make evidence-based recommendations to eradicate iodine deficiency in the UK.
Iodine has not only received lots of attention within the nutrition community, but for many decades has also been of great interest to medical practitioners. In the past iodine was renowned for its ability to treat a wide range of conditions including atherosclerosis, infectious diseases, depression and ovarian cysts and for this reason it was considered a Universal Medicine by doctors. Iodine fell out of favour as antibiotics and other drugs took their prominent positions in modern medicine and concerns emerged regarding side effects of high doses but interest in iodine is increasing again and its once expansive therapeutic use is giving scientists clues as to its broad range of physiological functions.
Physiological functions of iodine
Most of the physiological effects of iodine are due to the fact that this nutrient is an essential component of the thyroid hormones thyroxine/tetra-iodothyronine (T4) and tri-iodothyronine (T3), as well as the lesser known di-iodothyronine (T2) and mono-iodothyronine (T1). The role of thyroid hormones is to regulate metabolism – the rate at which we produce and use energy, and they do this by facilitating the entry of nutrients into the cell and then facilitating conversion of these nutrients into energy within the mitochondria. If iodine levels are insufficient and the thyroid hormone balance is disturbed energy production will be altered, and as energy is required for all biochemical reactions, the effects will be very far-reaching.
In addition to thyroid hormone production it appears that iodine has other important functions in the body. Iodine is known to be a potent antioxidant and has been shown to increase the total antioxidant status in human serum, this mineral also appears able to reduce inflammation and may have a normalising effect on stress hormone secretion2,3. Research indicates that iodine also has a role to play in supporting the antimicrobial actions of the immune system. More research is required to gain a full understanding of iodine’s involvement in maintaining healthy immune defences but certainly when it comes to a therapeutic role as an antimicrobial, iodine is renowned for its abilities displaying a broad spectrum of activity against bacteria, mycobacteria, fungi, protozoa and viruses. Before the advent of antibiotics iodine was a commonly used and important weapon for doctors treating patients harbouring pathogenic microorganisms and with the growing problem of antibiotic resistance, iodine and other natural antimicrobial agents may feature more prominently in future medical practice.
One of the reasons scientists have been convinced that iodine has important roles beyond thyroid hormone production is the fact that other organs besides the thyroid gland accumulate significant levels of this mineral. Organs and glands with a particular affinity for iodine include the breasts, ovaries, uterus, prostate, pancreas, salivary glands, parotid glands, thymus gland, stomach and skin. Interestingly, it appears that different chemical forms of iodine are preferentially taken up by different tissues, with the thyroid utilising the reduced form, iodide (I–), and the breasts, prostate and certain other glands having greater affinity for molecular iodine (I2). Although the role of iodine in these tissues is still largely unknown it is suggested that it’s required for their integrity as there is evidence of tissue deterioration when iodine is deficient.
Even though iodine has received lots of attention from the nutrition and medical community still surprisingly little is known about how exactly this nutrient is digested, absorbed and metabolised. There are also many gaps in the knowledge with regards to the precise physiological functions of iodine, particularly its activities outside of the thyroid gland. As scientists learn more about the basic science of iodine, its importance as a nutrient and its potential as a therapy will become clearer.
Iodine and cancer
An area of health where iodine has generated significant interest is cancer, prompted in part by evidence linking iodine deficiency with several forms of the disease4. Other research has identified a number of mechanisms by which iodine may protect against cancer. For example, apart from the antioxidant actions of iodine, this nutrient also appears to induce apoptosis (natural cell death) in cancer cells in certain situations and it may also encourage cellular differentiation (cancer cells are marked by their loss of differentiation)3.
It is the molecular iodine form rather than iodide that appears to possess most of these anticancer effects but that doesn’t mean that iodide is redundant when it comes to cancer protection. It is iodide that is required by the thyroid for the manufacture of thyroid hormones and if thyroid function is compromised this will undermine energy production within the mitochondria. Increasingly it appears that disturbed metabolism and compromised mitochondrial function have a key role in cancer development and progression.
Breast cancer has received particular attention when it comes to links between cancer and iodine and this is partly due to lower breast cancer rates in Japan where iodine intake is significantly higher than the Western world. A group of Mexican researchers including Aceves, Anguiano and Delgado have conducted a lot of laboratory and animal studies exploring how iodine may protect breast tissue against cancer and reverse particular tissue changes associated with the disease5,6. Human cancer studies are not yet available but clinical studies investigating the non-cancerous condition, fibrocystic breast disease in women indicate that molecular iodine supplementation can successfully treat this condition2.
Like the breasts, the prostate has a high affinity for iodine and the same group of Mexican scientists plus other researchers have begun to investigate the potential effects of iodine in helping protect prostate tissues against cancer. For example, a recent study found that molecular iodine and iodide prevented proliferation and induced apoptosis in prostate cancer cells7.
Growing awareness of the potential role of iodine in protecting against and even treating cancer has led to interest amongst those diagnosed with cancer, possibly you included. This interest has been fuelled by the work of several American doctors, in particular Dr Guy Abraham, Dr David Brownstein and Dr Jorge Flechas, who have done much to highlight the value of iodine as a supplement. For those of you interested in using iodine to support yourself with cancer I will discuss supplementation a little further on but before I do that I think it is important to first consider why it is some of us could be lacking in this essential mineral.
Why are we lacking in iodine?
The richest dietary sources of iodine are seafoods including saltwater fish, shellfish and seaweeds, although the iodine content does vary when it comes to seaweeds and it seems those brown in colour have the highest content. Other foods rich in iodine are dairy products due to livestock being encouraged to lick salt blocks containing iodine, and also eggs and meat, depending on the diet of the animals. Many plant foods also contain some iodine in lower amounts but exactly how much depends on the content of the soil they are grown in. Soil levels of iodine are deficient in many parts of the world (130 countries) including parts of Europe and therefore the iodine content of many foods is hit and miss. Iodised salt is a key source of iodine in many countries but salt is not iodised in the UK at this time.
Overall, iodine deficiency has decreased globally over the last few decades. However, experts are concerned that there has been a re-emergence of deficiency in some developed countries of late. For example, the proportion of the US population with moderate to severe iodine deficiency has more than quadrupled in recent decades8. A declining iodine intake in developed countries is linked to reduced salt intake in those countries where salt is iodised and reduced levels of animal products in the diet. But changing diet does not provide the only explanation as to why iodine levels could be falling as some experts believe that stress depletes iodine and chronic stress is a common problem of modern life.
At the same time that iodine intake may be declining, it’s possible that our need for this nutrient is climbing due to increasing levels of goitrogens in our environment. Goitrogens are compounds that promote enlargement of the thyroid gland and many do this by interfering with iodine uptake and utilisation. Certain chemicals in our environment, including heavy metals like mercury, also nitrates and pesticides, are thought to interfere with iodine uptake as well as certain medications, including a number of antibiotics and Lithium (used to treat bipolar disorder). Compounds present in our surroundings that contain fluorine, bromine or chlorine, elements that compete with iodine for its receptor, are also a potential problem. Fluorine in the form of fluoride is present in toothpastes and fluoridated drinking water, bromine and bromides are found in flame retardants, and chlorine and chlorides are widespread in our environment from our drinking water supply to bleaching agents used in many products. Some natural plant foods also contain compounds with the potential to disturb iodine metabolism, including cruciferous vegetables and foods containing isoflavones such as soya. However, many of these foods are very healthy in other ways and will have a negligible effects on iodine and the thyroid except perhaps when consumed raw in large amounts (juicing cruciferous vegetables on a daily basis is not recommended, particularly when thyroid health is already compromised).
So now let’s address the issue of iodine supplementation, something not as straightforward as it may sound. Although there is general consensus amongst nutritionally trained doctors and health practitioners regarding the benefits of iodine supplements for certain people, there is some controversy when it comes to the amount that should be given. As I mentioned earlier Drs Abraham, Brownstein and Flechas have done a great deal to highlight the role of iodine in health and how valuable it can be as a supplement, but their approach of using very high levels (often 50mg/day) has concerned other nutritional experts.
It does appear that many people taking the high doses of iodine recommended by the aforementioned doctors have experienced great benefits to their health and certainly according to Aceves and colleagues, plus others involved in iodine research, the dose of iodine required to achieve therapeutic benefits does need to be a great deal higher than the Recommended Daily Amount of 150mcg. However, it has long been known that iodine has toxic effects when used in excessive amounts and in particular the iodide form of iodine can be damaging to the thyroid.
Whilst iodide is essential for the normal functioning of the thyroid, too much can lead to autoimmune attack on the gland. Autoimmune conditions, which occur when the immune system starts destroying the body’s own tissues are a growing problem for reasons that are currently unclear. Autoimmune conditions related to the thyroid are Hashimoto’s Condition (results in underactive thyroid) and Grave’s Disease (results in overactive thyroid).
Underactive thyroid or hypothyroidism is a common problem in the UK resulting in symptoms such as fatigue and weight gain and possibly an increased risk of breast cancer. Whilst hypothyroidism can be due to nutrient deficiency, particularly iodine, autoimmunity is now the leading cause of hypothyroidism in developed countries such as America. In other words, many people diagnosed with hypothyroidism have Hashimoto’s Condition, although they may not be aware of this as GPs often don’t test for thyroid autoimmunity except in special circumstances. The upshot for these people is that taking iodine as a supplement may very well exacerbate their condition.
So as you can now appreciate, using iodine as a supplement has its complications. However, that doesn’t mean I’m recommending against it, not at all. As we’ve seen throughout this article, it is quite likely that you need more iodine than you are currently getting and if you have cancer there are many ways in which this nutrient could benefit you. What I am suggesting though is that if you are thinking of taking iodine in doses any higher than 1mg a day you have a thorough check of your thyroid first, including measurement of antibody levels to evaluate whether there is any underlying autoimmunity.
If there is no sign of autoimmune disease you could be a good candidate for iodine therapy in which case you’ll need to decide the appropriate dose and form to take. Because this is a complex area I suggest speaking to a nutritional therapist at this point but for general guidelines bear in mind that researchers such as Aceves and colleagues have found that iodine in the region of 3-15 mg per day was required to see positive changes within the breast and other tissues. Bear in mind also that molecular iodine is the form that demonstrates most powerful anticancer effects and carries less potential for damaging the thyroid, although iodide has potential anticancer benefits too, as previously discussed. Lugol’s solution is a liquid form of iodine with a long history of use. It contains both molecular iodine and iodide and is still a popular supplement used by health practitioners today. Other supplement forms of iodine include iodoral tablets, which again provide both molecular iodine and iodide, Thyadine which is a colloidal form of molecular iodine and potassium iodide (KI), which is the form found in most multivitamin preparations. By-the-way, if you were thinking of using kelp for your iodine, this may be fine if you only want small amounts of the nutrient but for a consistent dose of a higher intake kelp cannot be relied upon as iodine levels in seaweed are so variable.
How to safely optimise your iodine intake
Increasing research evidence and anecdotal reports indicate that iodine holds potential as a supportive treatment for those with cancer or those wishing to reduce their risk of the disease. If you have been inspired by this article and would like to optimise your iodine intake here are some simple guidelines to follow:
- Include seafood in your diet on a regular basis
- Choose a fluoride-free toothpaste
- Filter your drinking water to remove the chlorine
- If you suspect you may have been exposed to heavy metals consider having your heavy metals tested – discuss this with a health practitioner to determine the best test for you
- Consider having your iodine levels checked – discuss this with a health practitioner to determine the best test for you. Please note that the DIY skin patch test for iodine is not an accurate way of determining whether or not you need iodine.
- If you choose to take iodine as a supplement always make sure that you take a multivitamin and mineral alongside to ensure you are getting synergistic nutrients with your iodine. It is particularly important that you take selenium alongside iodine – for most people around 200mcg a day is sufficient
- If you would like to take iodine at doses higher than 1mg per day speak to a nutritional therapist for advice and make sure you have a thorough analysis of your thyroid function before taking the high dose supplements
- Vanderpump MP, Lazarus JH, Smyth PP et al. Iodine status of UK schoolgirls: a cross-sectional survey. Lancet. 2011 Jun 11;377(9782):2007-12.
- Patrick L. Iodine: deficiency and therapeutic considerations. Altern Med Rev. 2008 Jun;13(2):116-27.
- Aceves C, Anguiano B, Delgado G. The extrathyronine actions of iodine as antioxidant, apoptotic, and differentiation factor in various tissues. Thyroid. 2013 Aug;23(8):938-46.
- Venturi S, Donati FM, Venturi A et al. Role of iodine in evolution and carcinogenesis of thyroid, breast and stomach. Adv Clin Path. 2000 Jan;4(1):11-7.
- Aceves C, Anguiano B, Delgado G. Is iodine a gatekeeper of the integrity of the mammary gland? J Mammary Gland Biol Neoplasia. 2005 Apr;10(2):189-96.
- Soriano O, Delgado G, Anguiano B et al. Antineoplastic effect of iodine and iodide in dimethylbenz[a]anthracene-induced mammary tumors: association between lactoperoxidase and estrogen-adduct production. Endocr Relat Cancer. 2011 Jul 25;18(4):529-39.
- Aranda N, Sosa S, Delgado G et al. Uptake and antitumoral effects of iodine and 6-iodolactone in differentiated and undifferentiated human prostate cancer cell lines. Prostate. 2013 Jan;73(1):31-41.
- Hollowell JG, Staehling NW, Hannon WH et al. Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971–1974 and 1988–1994). J Clin Endocrinol Metab 83:3401– 3408, 1998.
As mentioned in the article, the use of iodine as therapy is a controversial subject in the world of nutritional medicine, with some experts recommending high doses and others suggesting that a more moderate intake is optimal. The following books and articles represent views on both sides of this argument.
Iodine: Why You Need It, Why You Can’t Live Without It by David Brownstein, Medical Alternatives Press 2009 – a very good book written by one of the main proponents of high dose iodine therapy
Why do I still have thyroid symptoms? by Datis Kharrazian, Elephant Press 2010 – highly recommended for those who suspect they may have an underactive thyroid
http://www.clinicaleducation.org/resources/reviews/iodine-deficiency-not-just-a-problem-in-developing-countries/ – excellent overview of iodine and its uses
http://www.townsendletter.com/Dec2008/iodine1208.htm and http://www.townsendletter.com/AugSept2005/gabyiodine0805.htm – the first of these articles puts forward arguments for high doses of iodine but in the second article Dr Alan Gaby, highly respected American doctor in the field of nutritional medicine, questions the need for such high doses of iodine
http://www.westonaprice.org/modern-diseases/the-great-iodine-debate/ – thorough and very balanced article on iodine and its benefits for health