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Iodine - The Forgotten Mineral

by Penny Crowther(more info)

listed in nutrition, originally published in issue 183 - June 2011

A hundred or so years ago iodine was recognized as a 'universal medicine' and was used to treat conditions such as infections, colds and lung diseases. It was recognized that people weren't getting enough of this essential trace mineral in their diets. In order to prevent goitres, iodine was added to salt and to flour. In the 1940s iodine started to go out of fashion as pharmaceutical medicines developed. There was bias against the use of iodine by the medical profession due to (unfounded) safety concerns (known as Iodophobia).

The terrible earthquake in Japan in March of this year put the mineral iodine in the spotlight again. Tablets of potassium iodide, a form of iodine, were given out by the government in parts of Japan to prevent damage to the thyroid by radioactive by-products. Fear led some people to start stockpiling supplies of iodine.

How does iodine work in the body and what is it needed for? Apart from its protective effects on the thyroid gland in the midst of nuclear fall out, this much neglected and essential trace mineral, if in short supply, leads to a myriad of health problems.

Iodine concentrates in the thyroid gland where it is needed for the production of thyroid hormones which regulate body temperature, weight and energy. The breasts and ovaries in women also have an increased need for iodine and have high concentrations of this mineral. Some preliminary data suggests a link between iodine deficiency and breast cancer.[1] Iodine is also essential for a well functioning immune system, alkalises the body and has powerful antioxidant and detoxifying properties.

The following signs and symptoms may suggest the need for more iodine (they can also indicate other health problems so best discussed with a practitioner):

  • Cracks in the hands and heels
  • Chronic sinus infections,
  • Upper respiratory infections and mucus
  • Viral warts (verrucas)
  • Ovarian dysfunction, low or high oestrogen
  • Underactive thyroid gland
  • Fibrocystic breasts
  • Infertility
  • Fatigue/brain fog
  • Insomnia
  • Muscle aches and pains
  • Depression
  • Dry skin and hair

Iodine Deficiency
Recently iodine has started to come to public notice again as there is concern that deficiency is becoming more widespread than was previously thought. In 1998 the World Health Organisation recognized that iodine deficiency is the greatest single cause in the world of preventable mental retardation. Whilst this type of severe iodine deficiency is not common in developed countries, it seems that over the last 30-40 years we are getting a lot less iodine than we used to. Data for the UK and Ireland has shown that many parts of the country are not reaching an adequate daily intake of iodine.[2]

Iodine Deficiency in Pregnancy
Obtaining enough iodine in pregnancy and breastfeeding is vital for normal brain and nervous system development in the baby and young infant. Severe deficiency results in cretinism which involves irreversible mental retardation and sometimes severe speech and hearing defects. However, even mild to moderate deficiency causes lower intelligence in children.

A recent study carried out by medical scientists at the University of Dundee on 400 pregnant women, discovered that 40% of them consumed less than half the recommended intake of iodine.

What Causes Iodine Deficiency?
Iodine is one of the least abundant minerals in topsoils which means that vegetable crops grown on the land are not rich in iodine. Seawater is high in iodine, making sea foods are the principle source of this mineral.

Another reason for the lack of iodine is the increasing presence of substances called Halogens in our food and environment which displace iodine in the body. Iodine is a halogen, along with fluoride, chloride and bromide. Fluorine and chlorine are regularly found in tap water and bromine is added to food, drugs and pesticides. These three halides are not beneficial to health and block the amount and uptake of iodine in the body.

So iodine is not only in short supply in the first place but has to compete with increasing levels of these other potentially toxic halogens. A leading iodine expert Dr David Brownstein has found that iodine will bind to fluoride, chloride and bromide as well as mercury and remove these substances from the body.

RDA (Recommended daily amount)
The RDA for iodine is 150mcg, 220mcg in pregnancy and 290mcg during breast feeding. Many experts believe that the research shows we need more than 150mcg daily for optimal thyroid, immune and hormone function and possibly cancer prevention.

Safety of Iodine
Like other trace elements, you can have too much iodine. The European upper safety limit has been set at 600 mcg. However to put iodine safety levels in perspective, the Japanese consume around 100 times the RDA on a daily basis in their seaweed rich diet! Interestingly, they have lower levels of breast, endometrial and ovarian cancer and less fibrocystic breast disease.[3] After the Japanese earthquake, the government handed out short term use iodine tablets containing a huge dose of 130mg for adults.

Occasionally, people who have high levels of halogens in their bodies will initially feel unwell when taking iodine as a result of the toxic halogens leaving the body. People who are very deficient in iodine can be hyper sensitive to iodine supplementation. However this can be overcome by very slowly increasing the intake. Occasionally there is an allergy to iodine, which may be more likely if there is a shellfish allergy. Urine iodine levels can be tested through a nutrition practitioner - this test is not available on the NHS.

Iodine should not be supplemented with certain medications such as those for an overactive thyroid and high blood pressure. Anyone wishing to take iodine in higher doses than the RDA should only do so under the guidance of a practitioner.

Dietary Sources of Iodine
Iodine isn't abundantly found in the average diet. The richest dietary source of iodine, seaweed, isn't widely eaten in the UK. Examples are kelp, nori, kombu, and wakame. You can buy these seaweeds dried in health food shops to add to soups, casseroles or salads or sprinkle over rice dishes.

An approximate guide to the iodine content of various foods is given below: The amount of iodine in the same food varies considerably depending on animal feed, soil content and storage.

 Food  Approximate Iodine Content
 100g mackerel  140 mcg
 100g cod/ haddock  100 mcg
 100g atlantic salmon  76 mcg
 100g tuna  30 mcg
 100g sardines  29 mcg
 100g mussels  140 mcg
 100g lobster  100 mcg
 100g oysters  60 mcg
 1g Seaweed dulse  72 mcg
 1g seaweed wakame  32 mcg
 1g seaweed nori  16 mcg
 large egg  13 - 26 mcg
 112g cottage cheese  26 - 71 mcg
 30g Cheddar cheese  5 - 23 mcg
 250g natural yoghurt  87 mcg
 banana one medium  3 mcg
 vegetables average  32 mcg
 baked potato medium with peel  60 mcg
 bread (regular) 1 slice  35 mcg

Regular table salt contains added iodine, but this type of salt is not recommended at all as it is processed and stripped of the trace minerals that are present when salt is in its natural form.

Don't forget to obtain enough selenium, which like iodine, is not always in abundant supply from the average diet. Selenium is required for the metabolism of iodine and thyroid function. Brazil nuts are one of the richest dietary sources of selenium. Fish such as tuna and cod and turkey are also sources

2. The Lancet. Iodine deficiency-way to go yet. Lancet 2008; 372: 88. CrossRef | PubMed
3. Kibirige MS, Hutchison S, Owen CJ, Delves HT. Prevalence of maternal dietary iodine insufficiency in the north east of England: implications for the fetus. Arch Dis Child Fetal Neonatal Ed;89: 436-439. PubMed. 2004.
4. Lazarus JH, Parkes AB, Smyth PPA, Smith DF, Cloughley G. Iodine status in early pregnancy: relation to thyroid function. 13th International Thyroid Congress, Buenos Aires, Argentina. Thyroid Abstracts 15: 218. PubMed. 2005.
5. Nawoor Z, Burns R, Smith DF, Sheehan S, O'Herlihy C, Smyth PP. Iodine intake in pregnancy in Ireland-a cause for concern?. Ir J Med Sci: 175: 21-24. CrossRef | PubMed. 2006.
6. Cann S., Netten J., Netten C., Hypothesis: Iodine, selenium and the development of breast cancer, Cancer Causes and Control 11:121-127, 2000.  Stadel B., Dietary Iodine and Risk of Breast, Endometrial, and Ovarian Cancer, The Lancet, 1:890-891. 1976.

Further Reading
Brownstein D. Iodine: Why you need it. Why you can't live without it. 104. West Bloomfield, MI: Medical Alternatives Press. 2008.


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About Penny Crowther

Penny Crowther BANT CNHC qualified as a nutritional therapist in 1997 and has been in clinical practice ever since. She has seen several thousand clients over the years, at her practice in London and online. Penny now specializes in nutrition for women in their 40s and beyond, particularly around peri and post menopause. Mid Life for women can be a time when fluctuating hormones play havoc with your wellbeing. In the midst of all the publicity around HRT, it's easy to forget just how powerful diet and lifestyle changes can be when it comes to navigating the menopausal years.

Penny will guide and support you through specific changes to your diet, targeted to you specifically, in midlife. She provides practical, easy to follow menu plans with easy and delicious recipes. The food you eat affects every cell and system in your body. It optimizes how you look and feel, both mentally and physically.

To book an appointment view consultation options here >>

As well as being a regular columnist for Positive Health, Penny has written for Holland and Barrett, and contributed to articles for the Daily TelegraphThe Times Literary supplement, Pregnancy & Birth and Marie Claire. She has been featured in the Daily Express, Daily Mirror and on local radio.

Penny is a registered nutritional therapist with standards of training endorsed by BANT (British Association for Applied Nutrition and Nutritional Therapy) and CNHC. This includes completing 30 hours of continuing professional development, annually.

Penny’s approach to health is holistic, and takes into account emotional, mental and environmental factors as well as nutrition. She has trained in coaching and studied many complementary therapies before qualifying as a nutritionist, which provides a broad foundation of knowledge in her nutrition practice. Penny may be contacted on Tel: 07761 768 754;

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