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FAQs about Iodine Nutrition
What is iodine and where does it come from?
Iodine is a naturally occurring chemical element, like oxygen and iron. Iodine is present in fairly constant amounts in seawater, but its distribution over land and fresh water is uneven. In continents such as Australia and New Zealand, natural iodine levels are very low in the soils where we grow our vegetables, grains and graze livestock.
Why do we need iodine?
Insufficient iodine in the diet results in a range of conditions known as Iodine Deficiency Disorders. Iodine deficiency is becoming an increasingly common cause of thyroid health problems in Australia.
Is iodine deficiency common?
New research shows that thyroid disease affects one in seven Australians.1
Fifty per cent of children and pregnant or breastfeeding women living in Australia have been shown to be iodine deficient, or at risk of developing thyroid disease.
What does my thyroid do?
Your thyroid gland is a critical part of your endocrine system. Its purpose is to secrete thyroid hormones that:
- control the metabolic rate of almost all cells in the body
- control the metabolism of fat and carbohydrates
- boost protein synthesis
- regulate heart rate and blood flow to organs
- are important for energy production and oxygen consumption in cells
- promote linear growth and brain development in children
- are needed for normal reproductive function in adults
- are important in bone and calcium metabolism
What happens if I don't get enough iodine?
Everyone needs iodine in their diet for healthy thyroid function and a healthy metabolism. Hypothyroidism (see symptoms below) can be caused by a lack of iodine in the diet, which prevents the thyroid from making enough of the necessary hormones.
Iodine deficiency is the single most common cause of preventable mental retardation and brain damage in the world. The most alarming consequences of iodine deficiency occur during foetal and infant development. Maternal iodine deficiency may cause miscarriage, other pregnancy complications, such as premature delivery, and infertility.
Thyroid hormones – and therefore iodine – are essential for normal development of the brain. If the foetus or newborn is not exposed to enough thyroid hormone, it may not survive or may have permanent mental retardation. Low birth weights may also result from iodine deficiency.
Iodine deficiency is a major cause of lowered IQ in children, according to leading international health authorities including the World Health Organization (WHO), UNICEF and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD). When the deficiency is very severe the effect can be up to 15 IQ points lower than normal (or a reduction of 15 per cent of the average IQ).2
How do I know if I have an iodine deficiency?
A person may have low iodine levels without showing symptoms. The most reliable way to check your iodine intake is to ask your doctor to order a urine test. Your doctor may also use a blood test to ensure that your thyroid hormone levels are normal.
The most visible consequence of iodine deficiency can be a goitre, or enlarged thyroid gland. A goitre can be difficult to detect in the early stages, especially in children. An ultrasound is the best method to measure the size, shape and texture of the thyroid.
Symptoms of hypothyroidism – which can be related to low iodine levels or other forms of "underactive" thyroid disease – include:
- lethargy and tiredness, muscular weakness and constant fatigue
- feeling cold (even on warm days)
- difficulty concentrating, slowed mental processes and poor memory
- unusual weight gain
- depression
- thick puffy skin or puffiness of the face
- hair loss
- dry skin
- constipation
- weak slow heart beat
- enlarged thyroid or goitre
What are the implications of iodine deficiency for Australia?
Iodine deficiency affects the whole community and can lead to increasing rates of thyroid disease amongst the general population, and higher rates of intellectual impairment in children. Based on overseas studies, it is also estimated that thyroid disease causes about $250 million loss in productivity in Australia each year.3 There are also the costs to the community for health services to support people with impaired development due to iodine deficiency.
How much iodine should I have in my diet?
WHO and UNICEF recommend the following daily amounts:
- age 0-7 years: 90 µg (micrograms or millionths of a gram);
- age 7-12 years: 120 µg
- older than 12 years, adult males and females: 150 µg
- pregnant and lactating women: 250 µg.4
How do I ensure I get an adequate intake of iodine?
Most of our iodine intake comes from what we eat and drink. The main sources of iodine are marine seafood, dairy milk or dairy products and foods containing iodised salt. Plant foods grown in iodine replete soils and meat from animals that have grazed in iodine replete areas only contain low levels of iodine.
International health agencies WHO, UNICEF and ICCIDD recommend that all salt in our diet be iodised. This is called Universal Salt Iodisation (USI).
Women who are pregnant, breastfeeding or considering pregnancy will benefit from taking an iodine supplement, that is safe and recommended to be taken during pregnancy, as part of their daily routine. Check the label to ensure that the iodine contained in each dose is at least 150 µg (micrograms). The only exception to this are women who have thyroid disease, in which case are advised to consult their doctor before taking an iodine supplement.
I am concerned about the use of salt in my diet?
Salt is a necessary part of a healthy diet. The daily recommended salt (sodium) intake for Australian adults is 2.3 to 5.9 grams.5 Most of the salt in the Australian diet comes from processed foods, therefore we should replace, as much as possible, our salt intake with iodised salt.
What if I have a low salt diet?
If you have a low salt diet, make sure the salt you do consume is iodised. A mineral supplement containing iodine can be a better source of iodine for those on a low salt diet. Consult your doctor before taking any supplements.
Can I take too much iodine?
Concern about iodine excess is not a reason to stop or avoid consumption of iodised salt, as the levels in salt are small enough to be tolerated by most people, except for those with a specific diagnosed thyroid autoimmune disease or an overactive nodular goitre. If in doubt, please consult your doctor.
1-5. References provided upon request.