What is iodine?

Iodine is an element that is essential for normal growth, and for brain development. A healthy diet needs enough iodine, but too much can cause health problems.

As food hygiene practices have changed, and less people consume iodised salt, iodine deficiency is becoming more common in Australia.

A radioactive form of iodine is sometimes used to treat certain thyroid conditions including hyperthyroidism and thyroid cancer — this is not the same as iodine found in food or dietary supplements.

What does iodine do?

Iodine helps the thyroid gland, in the neck, to make the hormone thyroxine. Thyroxine controls many of the ways certain body cells work.

Thyroxine is important for the growth of bones and nerves, and affects how proteins, fats and carbohydrates are used in the body (metabolism).

Iodine is especially important before birth and in babies and young children. It is essential for the development of the brain and nervous system, the 5 senses, alertness and coordination. Iodine deficiency is the most common worldwide cause of preventable mental retardation.

How much iodine do I need?

How much iodine you need depends on your age and stage of life:

Too little or too much iodine can cause problems.

Too little iodine is a risk factor for hypothyroidism (underactive thyroid). Symptoms of hypothyroidism can include:

• extreme tiredness
• feeling cold
• difficulty concentrating
• hair loss
• an enlarged thyroid (goitre), which shows up as a lump in the neck

Too much iodine (usually from supplements) can be dangerous, especially for people with thyroid disorders.

How do I get enough iodine?

You get iodine from the food you eat. Foods high in iodine include seafoods such as oysters, snapper and seaweed. Tinned salmon, bread, eggs, milk and dairy products such as yoghurt also contain iodine.

Iodine is also added to many types of salt. You can check on the label whether salt is ‘iodised’ (has added iodine).

Iodised salt is now used in commercial bread making, to help make sure all Australians get enough. The packaging will tell you how much iodine the bread contains.

Iodine and pregnancy

If you are pregnant, it’s important to check if you are getting enough iodine. Low iodine levels can increase the risk of a miscarriage. It can also lead to poor growth and intellectual disability in the baby.

The National Health and Medical Research Council recommends that anyone who is pregnant, breastfeeding or planning a pregnancy take an iodine supplement of 150 micrograms each day to top up their dietary intake. This will help ensure that they get all the iodine they need. Ask your doctor or pharmacist for more information.

If you are pregnant, avoid kelp (seaweed) supplements as these may contain varying levels of iodine and may contain heavy metals such as mercury that can be problematic during pregnancy.

If you have a thyroid condition, check with your doctor before taking an iodine supplement. Iodine supplements aren’t recommended for people with certain thyroid conditions.

Resources and support

• Visit Nutrition Australia for more information about iodine and your health, and recipes that are rich in iodine.
• Pregnancy, Birth and Baby has information on vitamins and supplements in pregnancy.
• NSW Health’s iodine supplements factsheet gives iodine requirements before conception, during pregnancy and while breastfeeding.