Iodine – the forgotten mineral

Are you Iodine deficient?

Iodine is needed for the production of thyroid hormones which regulate body temperature, weight and energy. In women, the breasts and ovaries 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. 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

A brief history of Iodine

A hundred or so years ago iodine was recognised as a “universal medicine” and was used to treat conditions such as infections, colds and lung diseases. It was recognised 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).

Iodine deficiency

Recently iodine has started to come to public notice again as there is concern that deficiency is becoming more widespread. In 1998 the World Health Organisation recognised 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.

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. 

Iodine should not be supplemented with certain medications such as those for an overactive thyroid and high blood pressure.

In my practice, I only recommend iodine supplementation as part of a multivitamin and mineral.


The richest dietary source of iodine, seaweed, doesn’t tend to feature much in the average UK diet. 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.

Look for an organic seaweed which is certified free of all the most likely ocean-borne contaminants. This is important as seaweed can often absorb water pollutants.

Dietary sources of Iodine

As noted above, iodine isn’t abundantly found in the average diet.
The iodine content of the same food varies considerably depending on animal feed, soil content and storage. An approximate guide is given below:


Approximate Iodine content

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

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

1 The Lancet. Iodine deficiency—way to go yet. Lancet 2008; 372: 88. CrossRef | PubMed
2 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 2004; 89: 436–439. PubMed
3 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 2005; 15: 218. PubMed
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 2006; 175: 21–24. CrossRef | PubMed

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.