A senior dietician shares the best and worst foods for thyroid health

While thyroid conditions are commonly treated with medication, what you eat can also influence how well your thyroid functions and how you feel day-to-day. From key nutrients that support hormone production to common foods and supplements that may interfere with treatment, understanding the role of diet can make a meaningful difference in managing symptoms.

What does your thyroid do?

The thyroid may be small, but it has a big job, regulating everything from your metabolism and mood to energy levels and weight. When it’s out of balance, as in conditions like hypothyroidism, hyperthyroidism or Hashimoto’s disease, what you eat can play a meaningful role in managing symptoms and supporting your treatment. Hyperthyroidism occurs when the thyroid produces too much hormone, often leading to symptoms like rapid heartbeat, anxiety, and weight loss. Hashimoto’s disease, on the other hand, is an autoimmune condition that gradually damages the thyroid, typically causing it to become underactive over time. While medication is still essential, certain nutrients like iodine, selenium, zinc and iron are key to keeping your hormones in check – just as some foods and supplements can get in the way.

What happens if you have a thyroid condition?

If you have a thyroid condition, your body may either produce too little or too much thyroid hormone, both of which can throw your system off balance. Symptoms vary depending on the type, but may include fatigue, weight changes, sensitivity to temperature, hair thinning, brain fog, anxiety, or even irregular menstrual cycles. Because these symptoms are often vague and overlap with other health issues, thyroid disorders can sometimes go undiagnosed for years.

Thyroid diet advice is everywhere, but what should you actually follow?

If you’re living with a thyroid condition, you’ve probably tried to “heal your body” by relying on superfoods or cutting out things like gluten or dairy. With advice coming from all directions, it’s not always easy to tell what really works.

To clear up the confusion, we spoke with Grace Yanti, Senior Dietitian at Mount Elizabeth Hospital, about what dietary choices truly support thyroid health, and what’s often misunderstood.

What role does nutrition play in maintaining optimal thyroid function from a medical perspective?

The thyroid requires specific nutrients - iodine, selenium, zinc, among others - to produce and regulate hormones that control metabolism, energy, and growth. Both deficiency and excess of these nutrients can disrupt thyroid function. A balanced diet supports healthy thyroid function and overall well-being.

Which nutrients are most critical for thyroid hormone production and regulation? Which ones should be avoided or minimised?

Key nutrients include:

Iodine: The main building block of thyroid hormones (found in cod, shrimp, dairy products, like yogurt and milk)

Caution: Too much iodine, especially from supplements or seaweed, can worsen thyroid issues in people with conditions like Hashimoto’s or Graves’ disease.

Selenium: Converts inactive T4* hormone into the active T3* form and offers antioxidant protection (found in Brazil nuts, tuna, sardines, eggs, whole grains

Zinc: Needed for hormone production and conversion (found in oysters, beef, lamb, pumpkin seeds, cashews, chickpeas and lentils)

Iron: Required for hormone synthesis (found in red meat, spinach, tofu)

Vitamin A: Supports hormone synthesis and receptor function (eggs, carrots, sweet potatoes, dark leafy greens like kale and spinach

Vitamin B12: Aids metabolism and hormone production (eggs, dairy products
fish like salmon, sardines, chicken, fortified plant-based milks (for vegetarians/vegans)

Tyrosine: An amino acid essential for thyroid hormone production (chicken, turkey, yogurt, cheese, soy products like tofu and tempeh, avocados, bananas, almonds)

How does diet impact the progression or management of Hashimoto’s?

Diet can help manage Hashimoto’s by reducing inflammation and supporting thyroid function. Some people notice improvements after cutting out gluten or lactose, eating less overall, or adding black seed (Nigella sativa). These changes may improve thyroid hormone and antibody levels, but restricting iodine doesn’t seem to help. Results vary widely between individuals, likely due to differences in thyroid health and nutrient status. While diet can be a valuable way to support your overall health, it should be seen as a complement to - not a replacement for - your prescribed medication. More research is needed, but diet can play a supportive role.

Is there a clinical basis for recommending gluten-free or dairy-free diets to Hashimoto’s patients?

For most people with Hashimoto’s, doctors don’t routinely advise gluten-free or dairy-free diets. There’s no strong evidence these diets help unless you have diagnosed celiac disease, gluten sensitivity, or lactose intolerance. In those cases, cutting out gluten or dairy should improve symptoms or medication absorption. Otherwise, cutting out these foods has no clear clinical benefit.

What is your view on anti-inflammatory diets for patients with Hashimoto’s?

Anti-inflammatory diets are widely seen as beneficial for Hashimoto’s. Eating plenty of fruits like berries, oranges and cherries, vegetables such as leafy greens and sweet potatoes, healthy fats like olive oil and fatty fish (salmon, mackerel), nuts (almonds, walnuts), and whole grains like quinoa and brown rice can help lower inflammation and support overall health. While these diets won’t cure the condition or replace medication, they may help ease symptoms and improve quality of life.  It’s also important to limit processed foods and added sugars, especially highly processed snacks, fast food, sugary drinks, and sweets, and to work with a healthcare provider to find what suits you best.

Can diet affect the absorption of thyroid medication like levothyroxine?

Yes. Foods and supplements such as calcium, iron, soy products, high-fiber foods, coffee, and tea can interfere with levothyroxine absorption if taken too close to the medication. To maximize absorption, levothyroxine should be taken on an empty stomach, 30-60 minutes before eating, and interfering substances should be avoided for at least 4 hours afterward. Consistency is key, and any changes in diet or supplements should be discussed with your healthcare provider.

Can weight gain linked to hypothyroidism be managed through diet?

Often, yes. Combined with medication and healthy lifestyle habits, a balanced diet focusing on whole foods, lean proteins, healthy fats, whole grains, fruits, and vegetables can help manage weight. Monitoring calorie intake and reducing processed and sugary foods also supports weight control. Consistency in eating habits is important for better overall health.

What dietary strategies help manage symptoms like weight loss or bone thinning in hyperthyroidism?

A diet rich in energy and protein, such as lean meats, eggs, and whole grains is recommended. Smaller, frequent meals help maintain energy. Adequate calcium and vitamin D are essential to support bone health. Managing iodine intake and staying well-hydrated are also important. Tailoring the diet to individual treatment plans with a healthcare provider is advised.

Are there specific dietary risks for hyperthyroidism patients?

Excessive iodine intake poses a significant risk in hyperthyroidism, potentially triggering or worsening the condition, especially in Graves’ disease or thyroid autonomy. Common iodine sources include seaweed, kelp, iodized salt, and supplements. Monitoring nutrients like selenium, vitamin D, calcium, and iron remains important. Supplementation should always be guided by medical advice and blood tests.

Should patients take supplements like iodine, selenium, and zinc for thyroid health?

Iodine supplements should only be used if a deficiency is confirmed, as excess iodine can worsen thyroid conditions. Selenium may benefit some autoimmune thyroid conditions like Hashimoto’s, while zinc is important but supplementation should be based on testing. Taking these supplements without medical supervision can disrupt hormone levels or interact with medications, potentially making symptoms worse. Always consult a healthcare professional before starting supplements.

Are there any thyroid “superfoods” or “toxins” that are misunderstood?

Yes. Cruciferous vegetables (broccoli, kale) are generally safe in moderation and don’t harm the thyroid. Soy rarely affects thyroid function if iodine intake is sufficient, though those on thyroid medication should be cautious. Iodine supplements can be unnecessary or harmful if not needed. Gluten-free diets benefit only those with celiac disease or gluten sensitivity. Ultimately, a balanced, varied diet is the best way to support thyroid health rather than focusing on so-called “superfoods.”