There's no special diet that treats an underactive thyroid. The British Thyroid Foundation says there's no specific "thyroid diet" recommended when you're diagnosed with a thyroid condition (BTF). What matters most is a healthy, balanced diet, getting enough (but not too much) iodine, and timing food and supplements around your thyroid medicine so it's absorbed properly.
Key takeaways
- No food treats an underactive thyroid. In the UK, the main cause is Hashimoto's disease, an autoimmune condition, not diet (NHS).
- Don't add iodine, kelp or sea moss if you're being treated for an underactive thyroid (BTF).
- Brassicas such as broccoli and cabbage are fine in normal UK amounts. Soya can reduce how well your thyroid medicine is absorbed, so leave at least four hours between them (BTF).
- Timing matters. Take your thyroid medicine with water on an empty stomach, at least half an hour before eating or drinking anything, and four hours apart from calcium or iron (BTF).
Is there an underactive thyroid diet?
Not as a special eating plan. The NHS says the main cause of an underactive thyroid in the UK is Hashimoto's disease, where the immune system attacks the thyroid. Too little iodine in the diet is a rare cause in the UK (NHS). The standard treatment is medicine that replaces the missing thyroid hormone, with regular blood tests to check the dose.
Diet still matters for your general health, your weight, and how well your thyroid medicine is absorbed.
Key nutrients: iodine and selenium
| Nutrient | How much adults need | Good food sources | Supplement advice |
|---|---|---|---|
| Iodine | 140 micrograms a day (NHS) | Cows' milk and dairy, eggs, sea fish, shellfish; some plant-based drinks are fortified (NHS) | Not needed if you're on treatment for an underactive thyroid. Avoid kelp and sea moss (BTF) |
| Selenium | 60 micrograms a day for women aged 19 to 64 (NHS) | Brazil nuts, fish, meat, eggs (NHS) | NICE couldn't recommend selenium supplements for thyroid disease because of a lack of evidence (NICE NG145) |
Iodine. Your thyroid needs iodine, and most people get enough from a balanced diet. But more isn't better: the NHS says high doses taken for long periods could change the way your thyroid works (NHS).
Selenium. Get it from food rather than high-dose pills. Too much selenium can cause hair and nail loss, and the NHS says 350 micrograms or less a day from supplements is unlikely to cause harm (NHS). The British Thyroid Foundation notes that high-dose selenium (more than 300 micrograms a day) has been linked to higher death rates in research (BTF).
Soya, brassicas and other food myths
Broccoli, cabbage and cauliflower. These are sometimes called "goitrogens". The British Thyroid Foundation says you'd need to eat very large amounts before they became a real concern, and under normal UK dietary conditions they're not a problem (BTF).
Soya. Soya interferes with the absorption of thyroid medicine. If you eat soya, leave as long as possible, at least four hours, between it and your tablet (BTF).
Gluten. Cutting out gluten isn't a recognised treatment for an underactive thyroid. But people with autoimmune thyroid disease have a higher risk of coeliac disease (NHS). If you have gut symptoms, ask a GP about testing, and keep eating gluten until you've been tested, because avoiding it can make the result inaccurate (NHS).
Biotin. High-dose biotin (often in hair, skin and nail supplements) doesn't affect your thyroid itself, but it can distort thyroid blood test results. Stop it two days before a test (BTF).
Timing food around your thyroid medicine
Your thyroid medicine is best taken in the morning, with water, on an empty stomach, at least half an hour before eating or drinking anything, including tea and coffee (BTF).
| Food or supplement | Suggested gap from your thyroid medicine |
|---|---|
| Breakfast, tea, coffee | At least 30 minutes after your tablet (BTF) |
| Calcium supplements | 4 hours (BTF) |
| Iron tablets | 4 hours (BTF) |
| Soya | At least 4 hours (BTF) |
| Other supplements | At least 4 hours, unless told otherwise (BTF) |
Always follow your own prescriber's instructions and your medicine's leaflet.
Underactive thyroid and weight
Weight gain is common with an underactive thyroid, but usually modest. The British Thyroid Foundation says typically 5 to 10 pounds may be down to the thyroid, depending on how severe it is, and most of that is salt and water (BTF).
With treatment you can expect a small weight loss, usually less than 10% of body weight. Once your thyroid levels are back in range, your ability to gain or lose weight is the same as anyone else's (BTF). To see where you are now, try our thyroid symptom checker.
When to see a GP
See a GP if:
- you think you have symptoms of an underactive thyroid, such as tiredness, feeling cold and weight gain (NHS)
- you have an underactive thyroid and are pregnant or planning a pregnancy (NHS)
- you're thinking about starting iodine, kelp, selenium or high-dose biotin supplements
- you notice a swelling in your neck (NHS)
Call 999 if a neck swelling makes it hard to breathe (NHS).
For more on the signs, read our guide to thyroid symptoms in women, or thyroid blood test results if you already have results. Our thyroid service can arrange testing and a clinician review.
If you have not been tested yet, our guide to getting a thyroid test in the UK explains the NHS, private and at-home options.
Honest FAQs
What foods should I avoid with an underactive thyroid?
Most people don't need to avoid any foods. Avoid kelp, sea moss and iodine supplements, and leave at least four hours between soya and your thyroid medicine (BTF).
Can I eat broccoli and cabbage with an underactive thyroid?
Yes. The British Thyroid Foundation says brassicas aren't normally a problem in a typical UK diet (BTF).
Can I drink coffee with my thyroid tablets?
It's best to wait. Take your thyroid medicine with water on an empty stomach, at least half an hour before eating or drinking anything (BTF).
Should I take selenium for an underactive thyroid?
NICE couldn't recommend selenium supplements for thyroid disease because there isn't enough evidence (NICE NG145). Food sources such as fish, eggs and Brazil nuts are the usual way to get it.
Will I lose weight once my thyroid is treated?
Often a little, usually less than 10% of body weight. After that, weight works as it does for anyone else (BTF).
This article is general information, not medical advice. Always speak to a qualified clinician about your own symptoms.
