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Iodine

Iodine is essential in our diet to ensure the thyroid gland in our neck functions normally. The thyroid is responsible for growth, brain development and the rate at which we burn energy. Iodine deficiency can lead to thyroid disease such as goitre or hypothyroidism and impair brain development.

How much iodine do we need?

 Age (years)RDI* Iodine (µg/day)
Infants7-12 months110
Children1-390
4-890
Boys9-13120
14-18150
Girls9-13120
14-18150
Men19-70+

150
Women19-70+150
Pregnant women14-50220
Breastfeeding women14-50270

Who needs more and why?

Pregnant and breastfeeding women need more iodine to support the brain development of their growing babies. The Ministry of Health advises pregnant and breastfeeding women to take a daily iodine-only tablet (150 micrograms), along with eating iodine-rich foods. Visit the Pregnancy & Breastfeeding page for more details

Which foods contain iodine?

You can iodine from:

  • iodine-rich foods: seaweed (kelp, nori, kombu, and wakame) is an exceptionally good source of iodine, seafood, eggs, milk and milk products are good sources.
  • foods fortified with iodine: bread, iodized salt.

Because of the low levels of iodine in New Zealand (NZ) soil, bread in NZ has to be fortified with iodine (except for organic and salt-free bread, and some bread mixes). Iodine has been added to salt since 1924. Note that some rock or sea salts sold in New Zealand are not iodised. Check the label to check if your bread or salt is fortified with iodine.

It is still important to limit, particularly if you have high blood pressure, but when you are cooking with salt, choose iodized salt.

Iodine supplements?

Iodine should only be taken on the advice of your doctor. Kelp supplements are generally not recommended as they can contain variable amounts of iodine and traces of other heavy metals (but note that eating kelp as food is perfectly healthy as part of a balanced diet).

 

Iodine deficiency

The iodine content of food is affected by soil, irrigation, fertilisers and cooking.  NZ soils are low in iodine, resulting in low iodine levels in locally grown foods.  Iodophores (cleaning products used by the dairy industry) were once the main source of iodine for NZers, but since the 1970s changes in industry practices have reduced the amount of iodine in milk. There has also been a decline in the use of iodised salt.  As a result, studies have shown the re-emergence of mild to moderate iodine deficiency across most age groups in NZ. Even at a mild level, iodine deficiency can affect hearing, intelligence and mental capability. Cases of severe iodine deficiency can result in goitre (swelling of the thyroid gland in the neck with associated lethargy) and hypothyroidism (caused by insufficient production of the thyroid hormone by the thyroid gland).

More info

 

Last reviewed: 10 March 2022

Last modified: March 10, 2022