Thyroid Health and Nutrition – What you need to know

This is an area where there's an enormous amount of misinformation online.

You'll find lists of "thyroid superfoods", foods you're apparently never allowed to eat and supplements promising to "boost" your thyroid.

For most women, it's much less complicated.

A varied diet provides the nutrients needed for normal thyroid hormone production and metabolism. There are, however, a few nutrients particularly worth knowing about.

Iodine and Thyroid Health

Your thyroid needs iodine to make thyroid hormones.

Good UK food sources include fish, dairy products and eggs.

But more iodine is not necessarily better.

If you already have a thyroid condition, taking high-dose iodine or kelp supplements can potentially make thyroid problems worse. The British Thyroid Foundation advises that people taking levothyroxine don't need additional iodine supplementation simply because they have hypothyroidism.

So I wouldn't reach for seaweed or an iodine supplement because you've read that it's "good for your thyroid".

If you eat very little or no dairy, eggs or fish – perhaps because you follow a vegan diet – your iodine intake is something worth considering with an appropriately qualified professional.

Selenium and Thyroid Health

Selenium is particularly interesting because the enzymes involved in converting T4 into active T3 are selenium-containing enzymes.

Food sources include fish, eggs, meat, beans, lentils and Brazil nuts.

Again, though, more isn't automatically better.

You don't need handfuls of Brazil nuts or a high-dose selenium supplement because you have a thyroid condition. Selenium deficiency can affect thyroid hormone metabolism, but supplementation hasn't been shown to be universally beneficial for everyone with hypothyroidism.

This is a good example of why I prefer a food-first approach unless there's a clear reason to supplement.

Iron Really Does Matter for Your Thyroid

Iron isn't just relevant because low iron can make you tired.

Your thyroid actually needs iron to make thyroid hormones.

An enzyme called thyroid peroxidase (TPO) is involved in the production of T4 and T3, and it depends on iron to function normally. Iron deficiency can therefore interfere with normal thyroid hormone synthesis.

This is particularly relevant for women who have heavy periods, because they're more vulnerable to developing low iron stores.

It's also another reason not to assume that tiredness, hair loss or feeling cold must have one single explanation. Low iron and an underactive thyroid can produce some very similar symptoms – and sometimes both need investigating.

One practical point: iron supplements can interfere with the absorption of levothyroxine, so they usually need to be taken several hours apart.

What About Broccoli and Other 'Goitrogenic' Foods?

This is one thyroid myth that needs some context.

Cruciferous vegetables such as broccoli, cabbage, cauliflower and kale contain naturally occurring compounds that can interfere with the way the thyroid uses iodine – which is where the advice to avoid them if you have hypothyroidism originally came from.

Cooking reduces the activity of these compounds, so cooked cruciferous vegetables are even less of a concern.

But does that mean you can't eat raw broccoli or kale if you have an underactive thyroid?

For most women, no.

Normal portions are unlikely to cause problems, particularly if your iodine intake is adequate. The concern is much more relevant to consuming unusually large quantities – for example, regularly drinking huge raw kale smoothies – alongside inadequate iodine.

So I wouldn't tell someone with hypothyroidism to stop eating broccoli.

These vegetables provide fibre and a huge range of useful plant nutrients. Enjoy them cooked regularly and don't panic about having a little raw sometimes either.

That's a much more sensible approach than adding another unnecessary food restriction.