Iodine can also be found in plant foods such as cereals and grains but the levels vary depending on the amount of iodine in the soil where the plants are grown.
In the UK, iodine can also be found in cows' milk.
How much do I need?
You should be able to get all the iodine you need by eating a varied and balanced diet. Adults need 0.14 mg a day.
What does it do?
It helps make the thyroid hormones. These hormones help keep cells and the metabolic rate healthy.
What happens if I take too much?
Taking high doses of iodine for long periods of time could change the way your thyroid gland works. This can lead to a wide range of different symptoms, for example weight gain.
What is our advice?
You should be able to get all the iodine you need by eating a varied and balanced diet. But if you decide to take iodine supplements it's a good idea not to take too much because this could be harmful.
Having 0.5 mg or less a day of iodine supplements is unlikely to cause any harm.