Iodine and Thyroid Health

The story of iodine

All the minerals needed by the human body originated in the earth’s crust and so are found somewhere in nature; iodine is found concentrated in the sea and around coastal areas.

This is a result of the last ice age when iodine was leached from the soil as the glaciers melted and carried the iodine into the rivers and out towards the sea.

This left vast areas of soil across the earth iodine depleted.

As a result, iodine deficiency is a big problem globally and a significant one as it can lead to irreversible physical and mental developmental delays in children, as well as fertility and metabolic problems in adults. The area between the Rockies and the Great Lakes was particularly affected in Canada.

Why is iodine important?

Iodine is concentrated in the thyroid gland, a little butterfly shaped gland at the front of the neck. It is a building block for the thyroid hormones, which are key hormones responsible for a healthy metabolism.

We don’t need much of this little mineral, a mere 150 micrograms a day, and more if you are pregnant or breastfeeding, see table below. However, a shortage can have profound effects including, poor concentration and memory, low mood, poor energy levels, dry skin, hair loss, infertility, weight changes, and poor digestive health.

However, it was concerns with a deficiency in the soil affecting pregnant and breast feeding mothers and the long term consequences to their children, which spurred Health Canada into action in 1949. Iodine deficiency can affect babies during pregnancy, infancy and into childhood resulting in irreversible stunted growth and intellectual disabilities. Health Canada mandated the fortification of table salt with iodine in 1949, which led to an immediate and significant decline in iodine deficiency in Canadians.

Iodine requirements

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*This includes sources of iodine from food and supplements.

Sources of iodine

  • The best sources of iodine are seawater fish and seaweeds such as arame, nori, wakame. Seaweeds are like the dark green leafy vegetables of the sea. Seaweed can be sprinkled on salads or added to soups and stews.

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Note: Avoid hiziki (hijiki) seaweed as this has been found to contain dangerous amounts of arsenic. Avoid kelp too as it contains too much iodine, which can also cause thyroid problems.

  • Freshwater fish have some iodine, but not as much as seawater fish.

  • Fortified table salt. Half a teaspoon of salt provides 190mcg of iodine.

  • Some foods can interfere with normal thyroid function, and are known as goitrogens. These include soy, and cruciferous vegetables (broccoli, cabbage, Brussels sprouts, cauliflower etc.). However, in the presence of enough iodine, these foods have very little to no effect on thyroid function. It is probably significant that in countries where soy and cruciferous vegetables are dietary staples, seaweed and fish are also commonly consumed. Lightly steaming or sautéing cabbage, broccoli and Brussels sprouts also markedly reduces any negative effects while preserving their nutritional value.

  • Environmental contaminants, specifically perchlorate, inhibits iodine uptake by the thyroid gland leading to deficiency. This is an emerging environmental concern with health implications for babies and children. Perchlorate is being found in food and water supplies and is in some plastic food wrapping. Some measures have been taken to control use of perchlorate in plastic wrapping. Wash all produce well and be cautious buying foods that are in contact with plastic.

  • Dairy is a source of iodine, however, it is not a natural source. The iodine in dairy comes from the iodine cleaners used in milk tanks. In Australia, the cleaning solution was largely changed from an iodine base and new guidelines were produced to ensure adequate intake from other sources. Indeed, the latest version of the Canada Food Guide puts considerably less emphasis on the consumption of dairy products and encourages eating more plant-based proteins. 

    With a plant-based diet, the nutrients of concern that are most often mentioned are protein, calcium, and iron. Iodine also comes from animal sources and dairy is indeed an important source of this little important nutrient. Coupled with the increasing move towards plant-based eating and removal of dairy from many popular diets, is it time to consider whether we should be concerned about an iodine deficiency?

  • Some prenatal supplements now contain 150mcg iodine. Pregnant and breastfeeding women have additional iodine requirements, as much as 50% more, so should consider topping up their iodine intake to ensure their daily intake is adequate. Breastfed babies are completely dependent on their mother’s breast milk for their iodine supply so ensuring the mother has enough iodine is key to the infant’s growth and development. If pregnant or planning to become pregnant, discuss iodine supplementation with your health care provider.

  • There is some evidence that pregnant mothers following a vegan diet may be low in iodine. If you are vegan and considering becoming pregnant, consider a supplement that contains 150mcgs of iodine. The book ‘Vegan for Life’ by Jack Norris and Virginia Messina is a great resource.

  • For gardeners in coastal areas, adding seaweed to the garden as a fertiliser and mulch is common practice. However, we are a little too far from the coast here, but garden stores stock liquid seaweed which can add some iodine, plus a host of other nutrients, to your garden. Your plants will love it and you will have nutrient rich produce.

In order to ensure adequate intake of iodine - particularly in light of the latest version of the Canada Food Guide - we may need to rethink some of the nutrients that are on our table, or indeed, not on our table.

Find out more on the iodine versus salt public health conundrum here.

If you have questions or concerns about whether you are getting enough iodine in your diet, schedule an appointment and we can discuss your individual needs.

All content provided on this website is for general information purposes only and is not intended to replace medical or specialist advice.

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