The thyroid glands convert iodine – usually from food, but sometimes supplements – into thyroid hormones.
These hormones, triiodothyronine and thyroxine, help keep cells and the metabolic rate healthy.
According to the US Office of Dietary Supplements it’s important for proper bone and brain development during pregnancy and infancy.
You can get iodine from food sources, such as sea fish and shellfish.
It can also be found in plant foods – such as cereals and grains – but the level depends on amount of iodine in the soil.
It’s recommended adults get 0.14mg a day.
The NHS suggest that it’s possible to get enough iodine from dietary sources.
However, some people may need to take supplements.