This post was written very quickly by a non-expert. Do your own reading before changing your diet!
You should make sure you get iodine:
- Unlike most countries, table salt in the UK is not iodised
- Most Brits get plenty of iodine from dairy
- Deficiency risk factors include being vegan, being female
- Iodine deficiency while (pre) pregnant or breastfeeding can cause IQ drop and even cretinism in the child
- For everyone else, symptoms are usually mild
- Buy iodised salt or even supplements. Careful, you can get too much.
On the last point: I take this potassium iodide supplement, which I recommend. (I take one capsule every two days.)
I looked into iodine supplements a while ago—the two main forms are potassium iodide and seaweed/kelp. Two or three legit-looking articles I found said that seaweed/kelp-based iodine supplements can contain very different amounts of iodine to what they say on their labels, which seems like a good reason to be wary. (Additionally, a couple other articles claimed that seaweed/kelp supplements contain high levels of toxic heavy metals, but the veracity of this claim wasn't clear to me.)