What does iodine do? The understanding nutrients series
We’re back with another edition of the understanding nutrients series! This time we’re looking at the mineral iodine. You can find the previous nutrients I’ve written about here.
Roles of iodine:
Iodine has many roles, but I’ll touch on the main one and
explain how it affects your body in different ways.
Thyroid hormones: iodine is a crucial part of the hormones made in the thyroid gland. The thyroid gland is in your neck and releases these hormones into the body. Triiodothyronine (also called T3), and thyroxine (also called T4) are the two key hormones that iodine helps to make. These two hormones have lots of functions but the key one is your controlling metabolism. Your metabolism is all the chemical reactions in your body, including the reactions that change the food you eat into energy that your cells can use.
There are hundreds of complex reactions that wouldn’t take
place if iodine wasn’t available to make the thyroid hormones.
Growth and development: as I said above, iodine is essential
for making the thyroid hormones. These hormones also play a role in growth and
development of babies. If these hormones are not present, then a foetus’s brain
and nervous system won't develop properly. And the baby will be at risk of
stunted growth and cognitive impairment once born.
How much iodine should you be having?
Iodine is not made in the body and so has to come from our
diet. You should be able to get all the iodine you need from a healthy balanced
diet.
The reference nutrient intake for adults for iodine is 140ug
(micrograms) a day. The reference nutrient intake is the amount of the nutrient
that will be enough for at least 97% of people. In pregnancy and breastfeeding,
the recommended amount is 200ug a day.
For reference, 100g of steamed cod has around 250ug of
iodine.
Sources of iodine:
Fish, eggs, dairy, and seaweeds are sources of iodine. But the iodine content in our food can vary a lot due to farming practices. And the amount we actually digest varies too. This isn’t a complete list but here’s some examples of sources of iodine for guidance.
- 100g haddock – approx. 400ug
- 100ml whole milk – approx. 30ug
- 100ml soya milk (fortified with iodine) approx. 22.5ug
- 1 egg – approx. 27ug
- 100g tinned tuna – approx. 12ug
- 25g of peanuts – approx. 5ug
- 10g of dried nori seaweed – approx. 147ug
What happens if you have too much iodine?
Iodine is one of the nutrients in which we have lots of
evidence of what happens if you have too much This doesn’t mean that you can’t overdo
it with other vitamins and minerals, but just that we know the risks of excessive
iodine intake.
Generally, most people will be okay with a high iodine
intake, but it’s recommended to not exceed 600 micrograms (ug) a day.
Too much iodine can affect your thyroid gland function. It
can lead to hyperthyroidism (also called overactive thyroid) which is where
your thyroid gland produces too much of the thyroid hormones. But it can also
go the other way and lead to hypothyroidism where your thyroid gland produces
too little thyroid hormones. These both can have devastating effects.
Hyperthyroidism can lead to: weight loss, fast/irregular
heartbeat, hand tremors, irritability, fatigue, and excess sweating. Medication
can be used to help the thyroid gland go back to functioning as normal.
Hypothyroidism can lead to: weight gain, weakness, fatigue,
constipation, sensitivity to cold, and dry skin and hair. If your
hypothyroidism is caused by consuming too much iodine, it’s treated by reducing
your intake of iodine or medications that mimic the thyroid hormones functions.
Seaweed and kelp are very high in iodine, so it’s advised to
limit these foods to no more than once a week to prevent an excess.
What happens if you don’t get enough iodine?
If you eat a healthy balanced diet, you should be able to
get all the iodine you need. But if your diet excludes foods like dairy and/or
fish e.g., people who follow a vegan diet, then you may be at a higher risk of
deficiency.
A lack of iodine leads to hypothyroidism, which is where you
don’t have enough thyroid hormones. It has the symptoms I’ve listed above like
weight gain, fatigue, and sensitivity to cold. But hypothyroidism caused by
lack of iodine also presents itself in the formation of a goitre. A goitre is a
large swelling in your neck and it’s your thyroid gland making itself larger in
an attempt to capture all the iodine that may be available in your body.
Having a goitre isn’t common in the UK. But if you have hypothyroidism, it's treated with iodine supplementation or medications that mimic the thyroid hormones.
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Key points:
- Iodine is an essential mineral needed for function of the thyroid gland. The thyroid gland helps control metabolism, and brain function in babies.
- Adults need 140 micrograms of iodine a day. Pregnant or breastfeeding women need 200 micrograms a day.
- The amount of iodine in food varies but fish, dairy, eggs, seaweed, and fortified products are sources of iodine.
- Hyperthyroidism is when you have too much of the thyroid hormones being created. It can lead to fatigue, weight loss, and a fast heartbeat.
- Hypothyroidism occurs when you have too little thyroid hormones being made. This can be caused by iodine deficiency. It can lead to a large swelling in your neck, weight gain, sensitivity to cold, and constipation.
I hope you enjoyed this blog post, and it gave you some
information about a little known nutrient!
Bye for now! 👋
References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4049553/
https://pubmed.ncbi.nlm.nih.gov/21802524/
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