Nutrition for thyroid health

If you have been told you have a thyroid condition, or you suspect you might, you have probably found conflicting advice about what to eat.

The thyroid gland produces hormones that influence energy use, temperature regulation, heart rate and digestion. The most common cause of an underactive thyroid in the UK is autoimmune thyroiditis (Hashimoto's disease), and an overactive thyroid is most often caused by Graves' disease (British Thyroid Foundation, 2023; NICE, 2019). As a Nutritionist, I also work with clients who have subclinical thyroid issues and are looking for support. 

A functional medicine perspective

Functional medicine looks at the person as a whole. It asks why a system may be under strain and considers nutrient status, digestive health, stress, sleep and lifestyle alongside a diagnosis. This approach provides a framework for asking broader questions when grounded in published evidence and a holistic, science-based perspective.

Key nutrients for thyroid health

Iodine

The thyroid needs iodine to make thyroid hormones. Milk, dairy and white fish are the main sources of iodine. UK research has found that mild iodine deficiency is present in some groups, including pregnant women (Bath et al., 2013), and that many plant-based milk alternatives contain very little iodine unless fortified (Bath et al., 2017). More is not better: excessive iodine, including from kelp supplements, can worsen some thyroid conditions, so I do not recommend high-dose iodine without medical guidance.

Selenium

Selenium is involved in thyroid hormone metabolism and in protecting the gland from oxidative stress. Food sources include fish, eggs, meat and Brazil nuts, though the selenium content of Brazil nuts varies widely.

Iron, vitamin D and B12

Low levels of these nutrients are common in people with autoimmune thyroid disease and can add to fatigue, which is easily mistaken for a thyroid symptom alone (Rayman, 2019). Testing through your GP is a good first step.

Food and medication: what to know

If you take levothyroxine, the timing matters. It is usually taken on an empty stomach, and certain products can reduce its absorption, including iron and calcium supplements (NHS, 2023; BNF, 2024).

Keep your routine consistent and check the patient information leaflet or ask your pharmacist about spacing. Do not change your dose or timing without advice from your prescriber.

Common myths

"Cruciferous vegetables like broccoli are off limits."

They contain compounds that can affect iodine uptake in laboratory conditions, but at normal dietary intakes, with adequate iodine, this is unlikely to be a concern. Cooking reduces the effect further (Rayman, 2019). They remain part of a healthy diet.

"Everyone with a thyroid condition should go gluten-free."

Autoimmune thyroid disease is associated with coeliac disease, and NICE recommends testing for coeliac disease in people with autoimmune thyroid disease (NICE, 2015). 

A practical starting point

If you’re looking to support your thyroid health through nutrition, these simple steps can be a good place to start:

• Follow the Eatwell Guide pattern: plenty of vegetables, wholegrains, beans and pulses, oily and white fish, and dairy or fortified alternatives (PHE, 2016).
• Check that your diet includes reliable iodine and selenium sources.
• Ask your GP whether iron, vitamin D and B12 levels have been checked.
• Keep medication timing consistent.
• Discuss any supplement with your GP or pharmacist first.

When to see your GP

Speak to your GP if you have persistent fatigue, unexplained weight change, feeling unusually cold or hot, palpitations, a swelling in your neck, or changes in mood or bowel habit. If you are pregnant or planning a pregnancy, tell your healthcare team about any thyroid condition, as your needs will differ.

This article is for general information and does not replace individual medical advice. Do not stop or change prescribed treatment without consulting your doctor.

References

Bath SC, Steer CD, Golding J, Emmett P, Rayman MP. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC). Lancet 2013;382:331–337.

Bath SC, Hill S, Infante HG, et al. Iodine concentration of milk-alternative drinks available in the UK in comparison with cows' milk. Br J Nutr 2017;118:525–532.

British National Formulary (BNF). Levothyroxine sodium. NICE. bnf.nice.org.uk

British Thyroid Foundation. Information on thyroid conditions. btf-thyroid.org

NHS. Underactive thyroid (hypothyroidism); Levothyroxine. nhs.uk

NICE. Thyroid disease: assessment and management (NG145), 2019.

NICE. Coeliac disease: recognition, assessment and management (NG20), 2015.

Public Health England. Government Dietary Recommendations, 2016; The Eatwell Guide, 2016.

Rayman MP. Selenium and human health. Lancet 2012;379:1256–1268.

Rayman MP. Multiple nutritional factors and thyroid disease, with particular reference to autoimmune thyroid disease. Proc Nutr Soc 2019;78:34–44.

SACN. Vitamin D and Health, 2016.

van Zuuren EJ, Albusta AY, Fedorowicz Z, et al. Selenium supplementation for Hashimoto's thyroiditis. Cochrane Database Syst Rev 2013;(6):CD010223.