Iodine and Selenium in Australia: The Soil Problem Nobody Talks About

Australian soils are low in iodine and selenium. Learn why, how mandatory bread fortification works, and what to look for in a mineral supplement.
By Health and Heal
3 min read

Australia has a mineral problem that begins in the ground. Our soils are among the most weathered and nutrient-depleted on earth, and two minerals in particular — iodine and selenium — occur at lower levels than in most other developed countries. That shows up in the food grown here.

This isn't fringe speculation. It's documented well enough that the Australian government changed food law over it.

Why Australian soil is low in iodine

Iodine reaches soil largely from the ocean, carried inland by rain. Australia's ancient, heavily leached soils have lost much of theirs over geological time, and vast inland areas sit far from any coast. Crops grown in low-iodine soil contain less iodine, and so does the milk and meat from animals grazing on it.

By the early 2000s, national surveys showed iodine intake had declined enough to concern health authorities. A contributing factor was a change in the dairy industry: iodine-based sanitisers, once widely used to clean equipment, were phased out, and they had been inadvertently adding iodine to the milk supply.

The bread fortification programme

In 2009, Food Standards Australia New Zealand made it mandatory for iodised salt to be used in most commercially produced bread. This is why standard bread contributes meaningfully to Australian iodine intake today.

There's a catch worth knowing about. Organic bread and bread mixes are exempt. So are most home-baked loaves unless you're deliberately using iodised salt. People who avoid commercial bread for dietary reasons — whether gluten-free, low-carb or organic — miss the country's main fortification channel entirely.

Selenium: the other depleted mineral

Australian and New Zealand soils are also naturally low in selenium compared with North America, where wheat grown in selenium-rich plains supplies far more. There's no national fortification programme for selenium.

Brazil nuts are the standout food source, though their selenium content varies enormously depending on where they were grown.

Why iodine and selenium appear together

The two minerals are metabolically linked. The thyroid contains the highest concentration of selenium of any organ in the body, and selenium-dependent enzymes are involved in thyroid hormone metabolism. Iodine is a structural component of thyroid hormones themselves.

Because of this relationship, supplement formulators commonly pair them rather than offering iodine alone — our Iodine, Selenium, Zinc & L-Tyrosine liquid drops are formulated on exactly that principle.

Who's most affected

The groups with the highest requirements or lowest intakes include:

  • Pregnant and breastfeeding women, whose iodine requirements are substantially higher (the NHMRC recommends supplementation, so speak with your doctor or midwife)
  • People who avoid commercial bread
  • Those following plant-based diets, since dairy and seafood are major iodine sources
  • People using non-iodised salts such as pink Himalayan or sea salt, which typically contain little iodine

What to look for in a supplement

  1. Check the elemental amounts in micrograms, and compare them against the NHMRC nutrient reference values.
  2. Don't assume more is better. Iodine has an upper intake level, and exceeding it is not harmless. Follow label directions.
  3. Look for tested sourcing, especially in liquid formulations.
  4. Talk to your doctor first if you have a thyroid condition. This one isn't optional. Anyone with an existing or suspected thyroid condition should not begin iodine supplementation without medical advice.

If you'd rather get selenium and zinc as part of a broader daily formula, our men's multivitamin with zinc and selenium is another option to compare labels against.

Frequently asked questions

How do I know if I'm getting enough?

Your doctor can arrange appropriate testing. Don't self-diagnose.

Does sea salt contain iodine?

Usually very little. Only salt labelled "iodised" is a reliable source.

Is seaweed a good source?

Seaweed contains iodine, but levels vary wildly between species and batches, sometimes far exceeding the upper limit.

Products mentioned in this guide

Always read the label and follow the directions for use. Supplements should not replace a balanced diet. If symptoms persist, talk to your health professional. If you have a thyroid condition, are pregnant or breastfeeding, consult your doctor before taking iodine supplements.