The thyroid gland regulates metabolism, energy production, body temperature, heart rate, and cognitive function — making thyroid health one of the most foundational aspects of overall wellbeing. An estimated 1 in 20 UK adults has some form of thyroid disorder, with women five to ten times more likely to be affected than men. Nutritional support for thyroid function is an evidence-based complement to medical treatment. See our iodine guide for the most important single thyroid nutrient.
The nutrients the thyroid needs
Iodine is the most critical thyroid nutrient — the thyroid gland uses iodine to produce T4 and T3 hormones. See our complete iodine guide for UK dietary sources and the re-emerging UK deficiency problem. Selenium is required for the conversion of T4 (inactive) to T3 (active) — Brazil nuts (2-3 daily provides adequate selenium), tuna, eggs, and sunflower seeds are the best UK sources. Zinc supports thyroid hormone synthesis and receptor sensitivity — found in meat, shellfish, legumes, and seeds.
Foods that can interfere with thyroid function
Goitrogens — compounds found in cruciferous vegetables (broccoli, cabbage, kale, cauliflower) and soy — can interfere with thyroid hormone production in large raw quantities. However, cooking reduces goitrogenic activity by 30-60%, and moderate consumption of cooked cruciferous vegetables is not a concern for most people. For those with hypothyroidism, the common medical advice to avoid excessive raw cruciferous vegetables and large quantities of soy is a sensible precaution rather than a prohibition.
Medication and nutrition interactions
Levothyroxine (the most commonly prescribed hypothyroidism medication in the UK) must be taken on an empty stomach — food, particularly calcium-rich foods, coffee, and iron supplements, significantly impairs its absorption. Waiting at least 30 minutes (ideally 60 minutes) before eating after taking levothyroxine is clinically important for medication efficacy. Many people are unaware of this interaction — it is one of the most common reasons for suboptimal hypothyroidism management despite correct prescribing.
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Frequently asked questions
Can you eat cruciferous vegetables if you have hypothyroidism?
Yes, for most people with hypothyroidism, cooked cruciferous vegetables are not a problem. Cooking reduces goitrogenic activity significantly, and moderate portions present no meaningful risk. The advice to restrict them is most relevant for people consuming very large quantities raw — not a typical dietary pattern.
What are the signs of iodine deficiency affecting thyroid function?
Iodine deficiency can present as fatigue, cold intolerance, unexplained weight gain, a slowed heart rate, and in more significant cases a visible goitre. Because iodine deficiency is re-emerging in UK populations — particularly in those who have moved away from dairy — it is worth discussing with your GP if thyroid symptoms are present.
Does selenium supplementation help with thyroid conditions?
Selenium is required for converting the inactive thyroid hormone T4 into the active T3 form. Evidence suggests selenium supplementation can reduce thyroid antibody levels in autoimmune thyroid conditions such as Hashimoto's thyroiditis, though the effect on symptoms varies. Dietary sources such as Brazil nuts, tuna, and eggs are adequate for most people who are not deficient.
Is there a link between gut health and thyroid function?
There is a growing body of evidence linking gut microbiome health to thyroid function. The gut influences the conversion and absorption of thyroid hormones, and intestinal permeability has been associated with autoimmune thyroid conditions. Maintaining microbiome diversity through a fibre-rich, varied diet is relevant to thyroid health, though the research is still developing.
Should people with thyroid conditions avoid soy?
Soy can inhibit thyroid hormone absorption when consumed at the same time as thyroid medication, so it is generally recommended to leave a gap of several hours between soy-containing foods and levothyroxine. For people not on thyroid medication, moderate soy consumption has not been shown to significantly impair thyroid function in those with adequate iodine intake.