Iodine

Iodine is an essential nutrient, which means your body cannot make it. You only need very small amounts. You must get it from your diet or from supplements.

Iodine is important because it allows your thyroid gland to make thyroid hormones. These hormones:

• keep your metabolism working correctly
• support normal growth and development in tamariki.

Iodine is essential for normal brain development so it is very important unborn pēpi and young tamariki get enough.

Iodine deficiency disorders include a wide range of health effects from having too little iodine. One serious health effect is goitre (enlargement of the thyroid gland leading to a swelling of the neck).

Goitre (enlarged thyroid gland)

In children, moderate and severe iodine deficiency can affect hearing and motor (movement) and cognitive (mental) function.

Children with very severe iodine deficiency can have low physical growth and intellectual disability.

Good sources of iodine can include:

• seafood (fish, shellfish and seaweed)
• milk, milk products and eggs
• commercially prepared bread
• iodised salt.

Iodine levels in meat, chicken, eggs and dairy products can vary because of the iodine content of the different animal feeds used.

Iodine levels in vegetables, fruits and grains vary with the iodine level of the soil in which they were grown.

New Zealand soils are low in iodine so many locally produced foods are low in iodine. This makes it difficult for most people to get enough iodine by eating these foods. It is also why commercially prepared bread products are now fortified with iodine (using iodised salt). This is a mandatory requirement for bread manufacturers.

It is best to choose iodised salt when using salt, but there is no need to increase how much salt you eat. Sea salt, rock salt and pink Himalayan salt are not good sources of iodine.

Iodine fortification of bread became mandatory in Aotearoa New Zealand in 2009. It includes most bread except for:

• organic bread
• non-yeast-leavened bread — bread products that contain no baker's yeast, such as some sourdough breads, flat breads and cornbread
• bread mixes.

Fortifying bread with iodine helps increase the amount of iodine in your diet.

You can find out more about the requirements for fortification at the Ministry for Primary Industries website.

Iodine fortification of bread and bread products — Ministry for Primary Industriesexternal link

Government monitoring of iodine status

There is regular checking of the iodine content of foods. The iodine status of the population is also measured, in particular for the most vulnerable groups, such as tamariki.

Pregnant women and other people taking iodine supplements

The need for iodine increases in pregnancy. Even with a nutritious, well-balanced diet, it is difficult for women to get enough iodine from food alone.

The Ministry of Health recommends pregnant and breastfeeding women take a registered 150 microgram (mcg) iodine-only tablet daily, as well as eating food sources of iodine. Iodine tablets are available at pharmacies.

While taking other iodine-containing supplements and kelp tablets will increase your iodine intake, you need to be careful with choosing to take this type of supplement. They can lead to iodine intakes above the safe upper limit. The margin between too much and too little iodine is very narrow, and the iodine content in seaweed products and kelp tablets is extremely variable.

Nutrients and supplements in pregnancy

Safe and healthy eating in pregnancy — HealthEdexternal link

Folic acid and spina bifida | Iodine and iodine deficiency — HealthEdexternal link

Dietary patterns that exclude foods that are good sources of iodine can increase your risk of iodine deficiency, for example:

• people who eat vegan or vegetarian diets, and who eat no eggs, fish or seafood products, and little dairy products
• people who eat very little commercially produced bread (bread is a major source of iodine in Aotearoa New Zealand).